• About This Glossary

• à grain

• abrasion

• absorbent ground

• acanthus

• additive

• alla prima

• anthemia (sing. anthemion)

• aqueous lining

• atmospheric perspective

• back frame

• backing board

• backscattered electron (BSE)

• basse

• beta radiograph

• beta radiography

• binder

• binding medium

• blocking in

• bole

• bolection

• bolt

• bolt match

• book-matched

• canvas

• canvas stamp

• cartouche

• cassetta

• chain lines

• China paper

• chine collé

• chisel

• cleavage

• color merchant

• commercially primed

• complementary color

• consolidant

• consolidate

• Conté crayon

• countermark

• counterproof

• cove

• craquelure

• cross section

• cross-sectional analysis

• crossbar

• cross-hatching

• c-scroll and s-scroll

• cusping

• darkfield illumination

• decape

• deckle edge

• delamination

• differential interference contrast (DIC) microscopy

• double thread fault

• drier

• dry mount tissue

• dry mounting

• drying cracks

• Duthuit

• Duthuit-Matisse and Duthuit

• edge lining

• electron microprobe analysis (EMPA)

• en plein air

• entablature and architrave frames

• escutcheon

• étude

• expansion-bolt stretcher

• extender

• fabricated black chalk

• facing

• figure

• filler

• fillet

• finishing

• fluorescence

• foldover

• Fourier transform infrared microspectroscopy (FTIR)

• foxing

• furnish

• gas chromatography mass spectrometry (GCMS)

• gesso

• gilding

• glaze

• glue-paste lining

• gouge

• graphite

• grisaille

• ground

• hardboard

• hatching

• haute

• ICA spring stretcher

• imitation or simulated deckle edge

• impasto

• impressed watermark

• inductively coupled plasma-optical emission spectroscopy (ICP-OES)

• infrared reflectogram

• infrared reflectography

• inpainting

• interleaf

• IRR

• Japanese paper

• Japanese vellum

• jelutong

• keying out

• keys

• laid lines

• laid paper

• lake pigment

• laminate

• lap joint

• laser-ablation-inductively-coupled-plasma mass spectrometry (LA-ICP-MS)

• lay-in

• laying in

• lean oil paint

• lining

• lisse

• lost-wax casting

• marine

• mat burn

• matrix

• metal soap formation

• miter

• mitsumata

• modeling

• moldmade

• monotype

• mount

• mounting

• natural black chalk

• natural-resin varnish

• ogee

• oil

• orthogonals

• overpaint

• ovolo

• palette

• palette knife

• panel

• patination

• paysage

• peinture claire

• pentimento (pl. pentimenti)

• perspective

• photomicrograph

• picture plane

• piece mold

• pigment

• plain weave

• Plasticine

• plein air

• ply

• polarized light microscopy (PLM)

• pouncing

• pre-primed

• preparatory layer

• primary cusping

• priming

• proof

• quadrillage

• radio opaque

• radio transparent

• raking light

• Raman microspectroscopy

• rebate

• relining

• repaint

• reposes

• reserve

• retouching

• roller

• sand casting

• scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX)

• scanning macro X-ray fluorescence spectroscopy (macro-XRF)

• scotia

• scumble

• secondary cusping

• selvage

• semiglaze

• sight edge

• sinking in

• size

• sizing

• skinning

• specular light examination

• spin

• spun

• sprue

• standard-size supports

• standard format

• stereomicroscopic examination

• stipple

• stippling

• strainer

• stretcher

• stretcher-bar cracks or creases

• strip frame

• stump

• stumping

• substrate

• support

• surface dry

• surface-enhanced Raman spectroscopy (SERS)

• synthetic varnish

• tacking edge

• tacking margin

• tapping out

• thread count

• thread-angle map

• thread-count match

• thread-density map

• tide lines

• tone

• torus

• transmitted-infrared imaging

• transmitted-light imaging

• twill weave

• ultraviolet (UV)

• ultraviolet radiation

• underdrawing

• underpainting

• value

• varnish

• vent

• warp thread

• warp-angle map

• warp-thread match

• warp-thread repair

• wash

• waste mold

• watermark

• wax-resin lining

• weave

• weave match

• weft snake

• weft thread

• weft-angle map

• wet-in-wet

• wet-on-wet

• wet-over-dry

• wove paper

• X-radiography

• X-ray

• X-ray fluorescence spectroscopy (XRF)

• Z spun

• About This Glossary

  • Several sources were particularly helpful in compiling this glossary: American Institute for Conservation of Historic and Artistic Works, Painting Conservation Catalog, vol. 2, Stretchers and Strainers (Paintings Specialty Group of the AIC, 2008); Nancy Ash, Scott Homolka, and Stephanie Lussier, Descriptive Terminology for Works of Art on Paper: Guidelines for the Accurate and Consistent Description of the Materials and Techniques of Drawings, Prints, and Collages, with Rebecca Pollak and Eliza Spaulding, ed. Renée Wolcott (Philadelphia Museum of Art, 2014), http://www.philamuseum.org/doc_downloads/conservation/DescriptiveTerminologyforArtonPaper.pdf; David Bomford, Jo Kirby, John Leighton, and Ashok Roy, Art in the Making: Impressionism, exh. cat. (National Gallery, London/Yale University Press, 1990); Anthea Callen, The Art of Impressionism: Painting Technique and the Making of Modernity (Yale University Press, 2000); Anthea Callen, Techniques of the Impressionists (New Burlington Books, 1982); Canadian Conservation Institute, Condition Reporting: Paintings, vol. 3, Glossary of Terms (Government of Canada, 1994), https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/condition-reporting-paintings-glossary.html; Anne F. Clapp, Curatorial Care of Works of Art on Paper (Lyons & Bueford, 1987); Francis W. Dolloff and Roy L. Perkinson, How to Care for Works of Art on Paper (Museum of Fine Arts, Boston, 1985); E. J. Labarre, Dictionary and Encyclopedia of Paper and Paper-Making, 2nd ed. (Swets & Zeitlinger, 1952); Ralph Mayer, The Artist’s Handbook of Materials and Techniques (Viking, 1982); Joseph Meder, The Mastery of Drawing, trans. Winslow Ames, rev. ed., 2 vols. (Abaris, 1978); Knut Nicolaus, The Restoration of Paintings (Könemann, 1999); Iris Schaefer, Caroline von Saint-George, and Katja Lewerentz, Painting Light: The Hidden Techniques of the Impressionists (Skira, 2008); Kimberly Schenck, “Crayon, Paper, and Paint: An Examination of Nineteenth-Century Drawing Materials,” in Jay McKean Fisher et al., The Essence of Line: French Drawings from Ingres to Degas, exh. cat. (Museum of Fine Art; Walters Art Museum, 2005), pp. 49–57; Silvie Turner, The Book of Fine Paper (Thames & Hudson, 1998); and James Watrous, The Craft of Old-Master Drawings (University of Wisconsin Press, 1957). Framing terms are taken from the glossary to Richard R. Brettell and Steven Starling, The Art of the Edge: European Frames, 1300–1900, exh. cat. (Art Institute of Chicago, 1986).

• à grain

  • By the late nineteenth century, commercially primed canvas—whether purchased ready-stretched or by the roll—was available in two principal thicknesses of ground application: à grain, indicating a single layer of ground; and lisse, indicating two layers. À grain preparations retain more of the canvas texture than lisse applications.

• abrasion

  • The removal of media from the surface of the artwork. When mentioned in condition summaries and previous conservation treatments, the term often refers to damage incurred through previous cleaning (with solvents or water) or physical contact with the paint surface. Abrasion by wiping or scraping back paint with a palette knife can also be part of the artist’s technique.

• absorbent ground

  • A type of ground particularly popular in the second half of the nineteenth century that, often due to its composition, absorbed some of the medium from oil paints, resulting in a faster-drying, matte surface. Although the composition of absorbent grounds varied greatly, many used large proportions of chalk and an aqueous binder such as glue as part of the mixture. See also ground.

• acanthus

  • A decorative motif based on the leaves of the acanthus plant, which has been used in architecture and the decorative arts since classical times.

• additive

  • Materials added to paint other than pigments and binders. These can include extenders and materials such as wax or resins, which may function to stabilize the paint or improve its working properties.

• alla prima

  • A method of painting without building up layers to achieve a form, but going directly to the final paint surface with minimal preparation, often working wet-in-wet. Also called direct painting (in French, au premier coup).

• anthemia (sing. anthemion)

  • A decorative motif consisting of a radiating cluster of leaves, based on the honeysuckle leaf.

• aqueous lining

  • A lining process that uses an aqueous, or waterborne, adhesive such as glue, paste, or a glue-paste mixture. See also lining.

• atmospheric perspective

  • A method of creating the illusion of depth by decreasing the color contrast and strength of borders, and by rendering colors cooler or bluer for objects in the distance, as if by an intervening atmosphere. Also called aerial perspective. See also perspective.

• back frame

  • The structural frame to which decorative carved moldings may be attached. Since the role of the back frame is not decorative, it is often made of wood inferior in quality to that of the carved moldings. The back frame is sometimes called a blind frame.

• backing board

  • Boards—currently often made from foamcore, Coroplast, or dibond, but in the past made from hardboard, cardboard and Masonite—attached to the verso of a painting to provide a buffer for fluctuating temperature and humidity and protection from grime and contact. These can be attached directly to the verso of a stretcher or held in place via pressure from the framing hardware.

• backscattered electron (BSE)

  • See SEM/EDX (scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy).

• basse

  • See standard-format supports.

• beta radiograph

  • An image of paper structure commonly recording watermark features, produced by beta radiography. See also beta radiography.

• beta radiography

  • A radiographic technique that uses a plane beta source to produce an image on radiographic film or computed radiography (CR) imaging plates to record watermarks and other structural characteristics of paper such as laid and chain lines and fiber distribution patterns. A thin polymethacrylate sheet containing radioactive carbon-14 is used. The carbon-14 isotope emits beta particles of low energy (150 keV), which can penetrate a sheet of paper. The technique is performed by first placing film or a CR plate on a flat surface. Then the sheet of paper is placed over the film or CR plate. The beta plate is then positioned on top of the paper, over the watermark or area of interest. Beta particles pass from the polymethacrylate into the paper and are absorbed by the denser areas of the paper yet pass through the thinner areas to strike the film or CR plate. Thus, the image generated, a beta radiograph, shows light and dark areas that correspond to areas of greater or lesser density, respectively, in the paper being examined, with watermarks highlighted in particular since they are thinner generally than the surrounding paper.

• binder

  • The material used to hold various solid, particulate components, including pigments and extenders, of paint together and to the ground or support layer. Traditional paint binders include linseed oil (oil paint), gum arabic (watercolor), or egg yolk (egg tempera). See also lean oil paint, oil.

• binding medium

  • See binder.

• blocking in

  • See laying in.

• bole

  • See gilding.

• bolection

  • A frame profile or section that projects beyond the plane of the painting at the inner sight edge and decreases in thickness to the outer edge. A typical profile would have a bold torus molding at the sight edge of the painting followed with a descending ogee or scotia and an outer smaller torus molding with a fillet and cove thin outer edge.

• bolt

  • The length of fabric, usually between 100 and 200 m in canvas preparation, created by a single length of warp threads on a loom. Bolts were further divided into rolls, which were individually sized and prepared for distribution to color merchants.

• bolt match

  • See weave match.

• book-matched

  • The two adjoining surfaces are produced from the same piece of wood, so that they have (almost) exactly the same grain appearance, but mirrored.

• canvas

  • Textile—usually composed of flax, cotton, hemp, or jute, or combinations of these—used as a primary support for painting and traditionally as a primary or secondary support for pastel or chalk drawings on paper.

• canvas stamp

  • See color merchant.

• cartouche

  • A decorative enclosure resembling a shield or scroll, often with boundaries of c-scrolls or scrolled foliage.

• cassetta

  • Definition to come.

• chain lines

  • Widely spaced lines formed in paper made on a laid mold screen, most clearly seen when light is transmitted through the paper sheet. See also laid paper.

• China paper

  • A smooth, relatively thin paper with characteristic brush marks throughout that are the result of the paper’s manufacture, specifically, the drying process. China paper is bulked with filler, usually kaolin clay, which lends it an opaque quality and gray tone.

• chine collé

  • A printmaking method whereby the image is printed onto a thin, China paper (the chine) that in turn is adhered, during printing, to a larger sheet of thick plate paper. The thin, absorbent China paper can record the finest marks from the printmaking matrix and yield prints of greater delicacy than possible with Western plate papers alone. The process was developed in the late eighteenth century for copperplate line engraving but since has been used as a support for all types of printing processes.

• chisel

  • A long-bladed hand tool with a beveled cutting edge and a plain handle that is struck with a hammer or mallet, used to cut or shape wood, stone, metal, or other hard materials.

• cleavage

  • A condition in which one or more of the layers of an artwork—including varnish, paint, and ground layers—are in the process of separating from the support or from each other. Causes of cleavage include shrinkage of the support and poor adhesion between or within layers. A common form of cleavage is cupping in which the edges along the cracks are raised.

• color merchant

  • Shop selling artists’ materials, including pigments, easels, palettes, oil paints, watercolors, drawing instruments, and supports. These became increasingly common in nineteenth-century Paris and sometimes provided additional services such as framing and restoration. In some cases, supports prepared by a color merchant bear a corresponding stamp on the support verso or stretcher. Also called colormen or marchands de couleur.

• commercially primed

  • Canvas supports prepared with sizing and ground layers in a large factory or a workshop of a color merchant instead of being primed in the artist’s studio. The result is a roll of pre-primed canvas that can be cut down, either by the artist or a color merchant, and individually stretched for painting.

• complementary color

  • Color opposite another on the color wheel: red and green, blue and orange, yellow and purple. When complementary colors are in close contact, the color of each is intensified. In the nineteenth century M. E. Chevreul’s treatise, The Law of Simultaneous Contrast of Colors (Le loi du contraste simultané des couleurs), published in 1839, was widely read by artists.

• consolidant

  • Material, usually solvent- or waterborne, used in conservation treatments to readhere lifting, broken, or flaking materials to the support.

• consolidate

  • See consolidant.

• Conté crayon

  • Fabricated drawing sticks. Although originally manufactured from powdered graphite, these crayons would later be comprised of pigments and clay to substitute natural black, red, and white chalks; depending on their manufacture they can produce powdery to slightly greasy characteristics.

• countermark

  • The smaller or subsidiary watermark found in addition to the main watermark. It serves to convey the name or initials of the papermaker, production date, or location. The countermark is usually placed on the second half of the sheet, opposite the main watermark. See also watermark.

• counterproof

  • A work of art made by pressing a sheet of paper against a freshly printed proof, resulting in a fainter image oriented identically to the design on the matrix from which the proof was pulled. Alternatively, an image created by pressing a sheet of paper onto a drawing in friable media such as pastel, whereby a mirror image of the drawing is transferred onto the paper. See also monotype.

• cove

  • A molding with a concave face.

• craquelure

  • Network of cracks.

• cross section

  • See cross-sectional analysis.

• cross-sectional analysis

  • For this type of analysis, a microscopic sample—including any combination of support, preparatory layers, paint, and surface layers—is taken, usually from the edge of an artwork or an area of loss, and mounted in a transparent resin. The resin block, once hardened, is ground and polished, exposing all the constituent layers of the sample in one plane. Cross sections can be observed and documented with a microscope in reflected light and ultraviolet fluorescence; they can also be subjected to analysis with SEM/EDX, FTIR, and Raman microspectroscopy.

• crossbar

  • An additional vertical or horizontal bar that functions to support the main stretcher or strainer members. Also called cross brace.

• cross-hatching

  • A technique in both painting and drawing in which volume or texture is created by two sets of strokes of varying interval and thickness, usually close to perpendicular to one another, that create a kind of X shape.

• c-scroll and s-scroll

  • Ornamental designs that refer to scrolls of paper, simplified into decorative bands in the basic shape of the letter c or s with simple volutes at each end. They are often used in linked patterns in combination with scrolling leaves and floral ornament.

• cusping

  • The pattern created along the edges of a stretched textile where the weave distorts in reaction to stretching and the attachment to a secondary support, such as a stretcher. Also called scalloping.

• darkfield illumination

  • An optical microscopy technique used for the examination of opaque samples, such as paint cross sections. The sample is illuminated from above through the objective and the light is reflected off of the sample so that it appears bright against a dark background.

• decape

  • A late 19th-and early 20th-century frame finishing technique in which old, damaged gilding is painted over with a translucent wash.

• deckle edge

  • An irregular (wavy or feathered) edge that is typically formed on all four sides of a handmade sheet of paper where pulp has seeped under the inner edge of the paper mold’s removable wooden frame (deckle) during formation; the deckle fits over the mold to contain the paper pulp as it drains through the screen surface.

• delamination

  • The separation of components of an artwork such as the original support from the lining.

• differential interference contrast (DIC) microscopy

  • A technique of illuminating and imaging microscopic samples that shows phase differences in the sample in a relief-like fashion. When examining cross sections with reflected light microscopy, DIC enhances certain aspects of the sample and also masks certain types of imperfections, such as scratches due to the grinding and polishing process.

• double thread fault

  • In Thread Count Automation Project terminology, a weaving defect in which two warp threads are temporarily woven as a single thread.

• drier

  • A compound added to oil paint mixtures to accelerate drying and hardening of the paint film. Typical drying agents are compounds of cobalt, manganese, and iron. Also called siccative.

• dry mount tissue

  • Tissue paper coated on two sides with a thermoplastic resin used to mount a work of art on paper to a secondary support without using a liquid adhesive. This mounting process involves placing dry mount tissue between the artwork and mount then subjecting them to heat and pressure in order to activate the adhesive and bond the artwork to the mount.

• dry mounting

  • Adhering two sheets of paper together using dry mount tissue.

• drying cracks

  • A condition of painted surfaces caused by uneven rates of drying between layers. Drying cracks can occur in the paint or varnish layers and tend to be wide with rounded edges. Also called traction cracks and shrinkage cracks.

• Duthuit

  • Depending on their medium, works included in the two existing catalogues raisonnés are identified by their catalogue numbers in one of the following resources: for prints, Marguerite Duthuit-Matisse and Claude Duthuit, Henri Matisse: Catalogue raisonné de l’oeuvre gravé, in collaboration with Françoise Garnaud, preface by Jean Guichard-Meili, 2 vols. (C. Duthuit, 1983); and for sculptures, Claude Duthuit and Wanda de Guébriant, Henri Matisse: Catalogue raisonné de l’oeuvre sculpté (C. Duthuit, 1997).

• Duthuit-Matisse and Duthuit

  • Marguerite Duthuit-Matisse and Claude Duthuit, Henri Matisse: Catalogue raisonné de l’oeuvre gravé, with the collaboration of Françoise Garnaud, 2 vols. (C. Duthuit, 1983).

• edge lining

  • The reinforcing of the tacking margins of a canvas painting by local lining along the edges of the support with a secondary fabric. Also called strip lining.

• electron microprobe analysis (EMPA)

  • A scientific method of analysis used to determine the composition of small volumes of samples. The instrument uses an electron beam to generate X-rays characteristic of the elements in a few cubic micrometers (μm) of a sample (1 μm = 1/1000 mm). This technique is able to give accurate quantitative analysis of the concentration of specific elements in an artist’s materials, even for small concentrations and for the analysis of lighter elements, such as sodium, aluminum, and silicon, that can be found, for example, in the pigment ultramarine blue.

• en plein air

  • See plein air.

• entablature and architrave frames

  • Neoclassical frames starting after the middle of the 18th century were often of these two basic sections types. Both terms derive from classical architecture and describe the structure of moldings that rests on and above the columns and capitals and beneath the pediment and roof. The architrave is the bottom portion. It rests on the capitals and is the beam between the columns, it is topped by the frieze and finally the cornice; the term entabalature refers to the entire combination. Generally the entababature frames are wider and have an outer projecting cornice like molding followed with a frieze and or an archtitrave bands, which are often fully or partially ornamented. Architrave is also used to refer to the moldings surrounding doors and windows. The architrave frame is simpler like these types of moldings, typically with an outer raised molding, an unadorned flat or shallow scotia center, and a narrow ogee molding on the inside at the sight edge of the frame.

• escutcheon

  • Keyhole cover.

• étude

  • A study made in preparation for a larger, more finished work (tableau). Often painted on a cheaper quality canvas.

• expansion-bolt stretcher

  • A stretcher developed by James LeBron in 1957 with Tite-Joint fasteners instead of keys to expand or contract the stretcher joints. It is still in use today. Also called a LeBron stretcher.

• extender

  • Inert additives, such as calcium carbonate (chalk), calcium sulfate (gypsum), and barium sulfate (barite) to paint and ink, intended to give bulk and dimensionality to the material. Kaolin (hydrated aluminum silicate or China clay) is often used as an extender in chalks, crayons, and pencils.

• fabricated black chalk

  • A commercially manufactured carbon black, particulate drawing material characterized by its intense black color, the minute size and rounded shape of the chalk particles, and the agglomeration of homogeneous particles in drawn strokes of the medium. Unlike [glossary: natural black chalk], sticks are formed with a water-soluble binder such as glue or gum arabic.

• facing

  • The act of applying paper material, often Japanese tissue, to part or all of an artwork to facilitate treatment or protect endangered paint layers. Often paintings were faced with tissue and wheat starch paste to stabilize the paint layer during the lining process. If this layer was not diligently removed after lining or consolidation, facing residues remain that can present aesthetic and structural problems over time.

• figure

  • See standard-format supports.

• filler

  • See extender.

• fillet

  • A molding that resembles a narrow, shallow step in profile.

• finishing

  • The process of filing down and polishing the surface after casting. Bronze castings need extensive surface finishing to remove sprues (pouring channels), vents (channels to allow gases and excess metal to escape), and raised ridges from joins between piece mold parts. During finishing, flaws in the casting would be repaired.

• fluorescence

  • Emission of visible light by an object or material when exposed to ultraviolet radiation.

• foldover

  • The crease made in a canvas where it is folded over stretcher or strainer bars. The original foldover corresponds to the first stretching of the canvas. If a canvas is mounted onto a new stretcher of slightly different dimensions, a new foldover is created. Also called turnover.

• Fourier transform infrared microspectroscopy (FTIR)

  • A technique that allows characterization of a vast array of materials, such as pigments, fillers, binders, and varnishes. A few microscopic particles of a sample are typically compressed into a thin film, placed under a microscope, and produce a graph—called a spectrum—that shows peaks at the discrete frequencies at which the sample absorbs the incoming infrared radiation. By interpreting and comparing this spectrum with a reference database it is possible to identify an unknown material. Using portable instruments, the technique can also be used noninvasively by collecting the infrared radiation that is reflected off the surface of the work of art examined, without the need to remove a sample.

• foxing

  • Small reddish-brown spots on paper typically produced by the chemical action of mold or metallic salts present in paper, activated by elevated humidity and temperature.

• furnish

  • The materials from which paper is manufactured. This term can be used to describe the type of plant fiber used in the raw stock (such as wood pulp and rag) as well as the general composition or combination of materials.

• gas chromatography mass spectrometry (GCMS)

  • A technique that allows the precise identification of organic materials such as those used in adhesives, varnishes, and paint-binding media. A microscopic sample is first treated by pyrolysis (controlled heating in an inert atmosphere) and/or chemical preparation to release volatile organic molecules. These are separated by the gas chromatograph (GC) and enter the mass spectrometer (MS), where they are fragmented in an electron beam. Mass spectra, representing “fingerprints,” or patterns of fragments formed from the sample molecules, are interpreted and compared with reference databases to identify the components of the sample. When used with a pyrolysis interface the technique is termed Py-GCMS; pyrolysis can also be performed in combination with a chemical reagent such as tetramethylammonium hydroxide in a technique known as thermally assisted hydrolysis and methylation, or THM-Py-GCMS.

• gesso

  • Traditional gesso used to prepare a frame for gilding is a mixture of a collagen glue, typically a parchment or rabbit skin glue, to which is added either calcium carbonate, calcium sulfate, Kaolin or a combination of these. It is applied while warm in thin applications in multiple layers. After drying the gesso can be recut to match underlying carved ornament, tooled into additional decorative patterns not included in underlying wood carving or molding, or trimmed and smoothed and polished to differenet degrees. In addition to covering any imperfection in the wood substrate, the gesso layer provides structure and base for application of colored burnishing clays (bole) and of the gold leaf.

• gilding

  • The application of gold leaf to prepared carved wood. There are two main types of gilding used in the finishing of frames: water gilding and oil gilding. In water gilding, the carved wood is first sealed with a water-soluble collagen glue (parchment glue and rabbit-skin glue being the most common). A white primer is prepared using the same glue, to which chalk or a similar substance (calcium sulphate or kaolin, for example) is added. This primer is generally called gesso. After several coats of this primer, the surface is smoothed. The smoothed gesso may be engraved or carved—this technique is called trimming in America—to add details or texture. A second, finer primer is made by combining the same adhesive with a clay-like material (hydrous aluminum silicate). Again, in America this material is called bole or burnish clay. White, red, yellow, and bluish-black are the most common colors; the latter three result from impurities in the material. Several light coatings of this bole are applied over the gesso. Together, the layers of gesso and bole constitute the gilding ground. Leaves of gold are cut to proper size on a special leather-covered cushion. The leaves are lifted with a wide thin brush called a tip, which, in order to make the delicate leaf cling to the brush, is made slightly oily by passing it lightly over the gilder’s cheek or hair. The ground is moistened, reactivating the adhesive in the bole, and the gold leaf is lightly set in place. After drying, the gilding may be left with a matte finish or it may be brought to a brilliant polish by burnishing it with various sizes and shapes of agate or hematite burnishers. In many frames, matte water gilding is juxtaposed with burnished water gilding for contrast. A variety of surface coatings may be used to tint and/or seal the finished gilding. In oil gilding, the primer may be the same as that used in water gilding, or it may be an oil-based white lead primer. If it is gesso-type primer, it must be sealed to render it non-absorbent. Any of a variety of oil-based sizes may be used as an adhesive for the gold leaf. The application of the leaf is the same as in water gilding. Oil gilding cannot be burnished, so it always has a matte effect. As with water gilding, a number of surface coatings may be used to enhance and protect the finished oil gilding. In some frames, both water gilding and oil gilding are used. Silver leaf may be used in place of or in conjunction with gold leaf in any variety of gilding. Since silver lacks the durable qualities of gold, it must always be sealed with a varnish to prevent tarnishing, and it is sometimes covered with an orange varnish to imitate gold leaf. Occasionally, cheaper substitutes for gold and silver leaf are used—copper and aluminum leaf are the most common. Neither of these substitutes, however, can be burnished in leaf form, and they are inferior in appearance to the precious metals. Gold and silver leaf can be pulverized, mixed with a painting medium, and applied like paint.

• glaze

  • A transparent or translucent paint layer, usually highly saturated and incorporating extra medium. Traditionally, glazes were used to add volume to form or to change the value and hue of a particular area.

• glue-paste lining

  • See aqueous lining.

• gouge

  • A chisel with partly cylindrical or curved blade, used to cut holes or any circular sweep. The blade can be sharpened on the convex or concave side of the curve.

• graphite

  • An allotropic form of pure carbon used by artists unprocessed as a stick or lump set into a port crayon (metal holder) or compressed into thin rods and encased in wood-cased pencils. In 1795 a substitute for natural and pure carbon, the fabricated graphite pencil, was invented in France. It consists of finely powdered graphite mixed with clay and water and fired at a high temperature. The ratio of clay to graphite determines the hardness or softness of fabricated graphite pencils. Soft pencils require very little pressure to lay down significant amounts of graphite on the surface, creating broad, dark lines, while hard pencils deposit less graphite on the surface and create fine, silvery lines.

• grisaille

  • Monochrome painting in shades of gray, black and white. Sometimes advocated as an underpainting to be glazed.

• ground

  • An opaque layer applied to the support, usually over a sizing layer, to prepare the canvas to receive paint. Thinner grounds, including á grain, leave more of the canvas texture apparent, while thicker grounds, including the double-layer lisse, mute the canvas texture. Grounds in the nineteenth century were commercially available in white and a variety of pale colors, and in both absorbent and nonabsorbent consistencies. Also called priming or preparatory layer(s).

• hardboard

  • A solid support made from pressed wood fibers.

• hatching

  • An area of parallel brush or drawing strokes of similar, relatively short length.

• haute

  • See standard-format supports.

• ICA spring stretcher

  • The Intermuseum Conservation Association (ICA) spring stretcher, designed by Richard Buck in 1950, is the most common type of spring-tension stretcher. It is constructed with spring-loaded corners intended to exert continuous, even tension on the canvas as it changes in response to fluctuations in humidity. The stretcher was available, under the name Superior Spring-Stretcher, until 2001.

• imitation or simulated deckle edge

  • An irregular edge found on opposite ends of a moldmade sheet of paper. They are formed by bands of rubber placed at regular intervals along the wire screen belt of a cylinder mold machine. Moldmade papers are hand torn along the imitation deckle edge during finishing. False deckle edges are narrower and more uniform than true deckle edges. Also see moldmade.

• impasto

  • Thick, textural application of paint.

• impressed watermark

  • A type of watermark found in machine-made paper where a design fabricated in relief, often in rubber, is affixed to a rolling cylinder (called a dandy roll) and rolled over the moving web of damp pulp, pressing the design into it. The impressed design is then visible in transmitted light similar to a watermark.

• inductively coupled plasma-optical emission spectroscopy (ICP-OES)

  • An analysis technique that allows identification and quantification of the atomic elements present in a sample such as a metal alloy or ceramic. Samples are introduced as a solution into an argon plasma in a process that excites the constituent atoms, which subsequently release energy, generating an emission spectrum. The individual elements can be identified by their characteristic emission lines (wavelengths) and quantified by the intensity of these lines.

• infrared reflectogram

  • See infrared reflectography.

• infrared reflectography

  • This technique exploits the varied transmission, absorption, and reflection properties of infrared radiation by artists’ materials. The degree of penetration depends on the thickness of the paint, the pigments used, and the wavelength of the infrared radiation. Many paints appear partially or completely transparent, while others, such as black, absorb the infrared radiation and appear dark. An infrared-sensitive camera captures the light reflecting from the artwork. The resulting image is known as an infrared reflectogram. Infrared reflectography is used to distinguish pigments, inscriptions, underdrawings (particularly those done in carbon-rich materials such as charcoal and pencil over a white or light-colored ground), and changes in a composition not visible to the naked eye.

• inpainting

  • Painting done by a conservator to restore areas of loss or damage in an original paint layer. Inpainting is limited to the area of loss and is carried out in a medium that remains readily distinguishable from the original, does not discolor, and can be easily removed in the future. Also called retouching.

• interleaf

  • Material between the layers of a lining, usually a secondary, inert fabric or a solid support such as hardboard.

• IRR

  • See infrared reflectography.

• Japanese paper

  • Typically handmade paper composed of the inner bark of the gampi, mitsumata, or mulberry plants. Although these papers do not contain a watermark, they often reveal faint mold impressions from the bamboo screens on which the paper sheets were made.

• Japanese vellum

  • A historical term used to describe a semitranslucent paper that resembles vellum. Produced in Japan, Japanese vellum is characterized as relatively thick, extremely smooth, and having long, lustrous paper fibers. It is durable and wear resistant. A poorer quality imitation vellum paper, called papier japon, is made by acid treating western wove paper to simulate a semitranslucent appearance, and was produced in Europe beginning in the late nineteenth century as a cheap alternative to imported Japanese vellum. Also called papier japon, simili-japon, and vellum paper.

• jelutong

  • Definition to come.

• keying out

  • The act of tapping the keys to expand the stretcher and increase tension on a canvas support. See also keys.

• keys

  • Small wedges, often roughly triangular in shape, inserted into the joints of a stretcher to allow the stretcher to be expanded and tension on the canvas increased. This process is called keying out or tapping out.

• laid lines

  • Tightly spaced, parallel lines imparted to paper by the laid wires of the paper mold, most clearly seen in transmitted light. See also laid paper.

• laid paper

  • A type of handmade or machine-made paper formed on a mold screen of closely spaced, parallel wires (laid lines) that are secured in place by widely spaced wires (chain lines) woven around the laid lines. When the paper mold is dipped into water containing a fine dispersion of paper fibers, the fibers settle selectively along the wires as the water drains off; the formed sheet bears the laid wire screen pattern that is most clearly seen when light is transmitted through the paper sheet. Handmade papers prior to the last quarter of the eighteenth century were formed on a single laid and chain screen secured along the chain lines to the wooden ribs of the mold. When the mold was lifted from the pulp to form the sheet, a slight vacuum was created by the ribs, causing thicker pulp formation along the chain lines, which appeared as shadows in the finished sheet. These shadows are characteristic of paper formed on a single screen (or single-faced mold); such sheets are sometimes referred to as antique laid paper. When a second set of wires is added between the screen and the ribs of the mold, suction along the chain lines is prevented, thus eliminating the shadows. Paper made on these double-faced molds, as they are known, is sometimes referred to as modern laid paper.

• lake pigment

  • A translucent pigment made by precipitating a dye onto an inert substrate. Lake pigments can be made from naturally-sourced or synthetic dyes; common examples include alizarin, madder and carmine (cochineal).

• laminate

  • A thick piece of paper formed when two or more pieces of paper are adhered to one another, either with an adhesive or under pressure exerted during the printing process.

• lap joint

  • A joint made with two pieces of timber by halving the thickness of each member at the joint and fitting them together so that adjoining surfaces are flush.

• laser-ablation-inductively-coupled-plasma mass spectrometry (LA-ICP-MS)

  • An analysis technique that allows highly sensitive elemental and isotopic analysis to be performed directly on a solid sample such as a metal alloy or ceramic. A laser beam is focused on the sample surface and vaporizes a very small amount of solid material—a process known as laser ablation. The ablated material is transferred by a gas stream into a high temperature plasma where it is ionized prior to analysis by mass spectrometry, which separates and quantifies the constituent atomic elements and their isotopes.

• lay-in

  • See laying in.

• laying in

  • The act of establishing either the major elements of a work in solid paint or the initial paint layers. The lay-in is a form of underpainting, also referred to as the ébauche or block-in.

• lean oil paint

  • Paint with a low oil binder-to-pigment ratio.

• lining

  • The act of structurally reinforcing the original canvas or paper support with a similar or like material to provide strength or reinforcement to the artwork. A painting can be lined with a second textile or canvas with an adhesive, typically aqueous materials, wax-resin mixtures, or BEVA 371 (a trademarked thermoplastic adhesive developed for the conservation field by Gustave Berger in 1971, containing varying amounts of ethylene vinyl acetate copolymer, ketone resin, and wax). Works of art on paper are traditionally lined with Japanese kozo (paper made of the inner bark fibers of the mulberry plant), adhered overall with prepared wheat starch paste.

• lisse

  • By the late nineteenth century, commercially primed canvas—whether purchased ready-stretched or by the roll—was available in two principal thicknesses of ground application: à grain, indicating a single layer of ground; and lisse, indicating two layers. A lisse (French for “smooth”) application fills the interstices of the canvas weave to a greater degree than à grain applications.

• lost-wax casting

  • A technique of casting metal sculpture. The process usually began with a gelatin mold, along with a rigid outer mold to keep the gelatin in shape while the wax model was made. The liquid wax was brushed and poured into the gelatin mold and swirled around to make a thin, even layer that would represent the thickness of the final metal sculpture; the excess wax was then poured out. Once the gelatin mold was removed, the artist could make any changes to the soft wax. Then, a heatproof material, called investment, was poured into the interior of the hollow wax to make the core and was carefully added in a thick layer to the exterior to make the outer mold. Pins were added to hold the outer mold and the core in alignment. The mold was then heated to melt out the wax, and the resulting empty space was filled with molten metal.

• marine

  • See standard-format supports.

• mat burn

  • Linear brown discoloration that develops over time in paper that is in direct contact with a window mat manufactured with inferior materials, such as wood pulp. Under certain atmospheric conditions, particularly with elevated humidity and temperature, acid from the window bevel of poor-quality mat board can migrate into the paper adjacent to it and cause oxidation of the cellulose.

• matrix

  • An object, such as a wood block, metal plate, or stone upon which a design is drawn for the purpose of making a print.

• metal soap formation

  • A condition in which new compounds form when metallic components in pigments or driers in the paint or ground layers react with fatty acids in the oil binder or varnish. Frequently these metal soaps form aggregates that can move toward the surface of a work, appearing as small, sometimes white protrusions or bumps. These protrusions can sometimes cause cracks, losses, and destabilization of the paint layer(s) over time.

• miter

  • A way of joining two abutting members such that both are carved at equal angles to create the desired angle of the joint. For example, in most frames and stretchers, both members would be cut at a forty-five-degree angle to make a ninety-degree joint.

• mitsumata

  • A paper fiber obtained from the bark of a shrub, Edgeworthia gardineri (formerly Edgeworthia papyrifera), that is native to Asia and cultivated in Japan. Mitsumata is one of three main fiber types used for making Japanese paper. It has soft, short, absorbent fibers that combine to make a very thin, translucent, and relatively weak paper.

• modeling

  • In two-dimensional art forms (such as drawing or painting), modeling is the depiction of three-dimensional objects achieved through the representation of light and shadow.

• moldmade

  • Paper produced on a cylinder-mold machine to imitate the qualities of handmade paper. The sheet is formed as a cylindrical mold covered with a metal wire screen revolves half submerged in a vat of pulp. A layer of pulp clings to the metal screen as it rises from the vat, then at the apex of the revolution, the pulp is transferred to another wire screen belt and transported to areas for surface finishing, drying, and cutting. A moldmade sheet has two natural deckle edges, formed by the parallel edges of the wire screen, and two false deckle edges. These are achieved by bands of rubber placed at intervals along the wire screen belt. Less pulp accumulates along these rubber bands, and the resulting line of thin pulp facilitates separating the continuous strip of paper into sheets by hand tearing. Sheet size is determined by the width of the cylinder mold and the distance between the rubber bands.

• monotype

  • A print, typically unique, made by painting on a smooth, unworked solid surface such as metal or glass and transferring the image onto paper by running it through a press or by hand burnishing. See also counterproof.

• mount

  • See mounting.

• mounting

  • In a process similar to lining, works of art on paper are adhered overall to a secondary support. For canvas paintings, mounting is a technique of affixing the work to a rigid support such as a board and is also called marouflage.

• natural black chalk

  • A black carbon-based material that is mined and cut into sticks to use for drawing. Natural chalk is comprised of fine, rounded particles and has an inherent hardness. Drawn lines appear less intensely black than fabricated black chalk.

• natural-resin varnish

  • A varnish made from a dissolved resin of natural (plant or insect) origin. Natural resins include damar and mastic.

• ogee

  • A molding that is S-shaped in profile; also called cyma reversa or cyma recta, depending upon the orientation of the curves.

• oil

  • In the present study, this term generally refers to drying oils used in artists’ paint, usually linseed oil but also poppy and walnut oils, among others. Drying oils form a hard film when exposed to air and cure over time.

• orthogonals

  • Lines drawn within the geometry of linear perspective to guide the scale and angular recession of objects and figures in space. Such lines extend into space perpendicular to the picture plane and represent parallel vectors.

• overpaint

  • Paint or restoration material applied over the artist’s original paint. Most often applied by another artist or a restorer at a later date, overpaint was used to cover damages and make aesthetic changes to the artwork. It is often excessive and is generally avoided in favor of localized inpainting.

• ovolo

  • A convex molding that is quarter circular in profile.

• palette

  • Either the range of colors used by an artist for a particular work, or the hard surface used by an artist to stage and mix colors.

• palette knife

  • A spatula-like tool used for mixing and applying paint and ground layers. Palette knives usually consist of a handle and a thin, flexible, blunt-tipped metal blade.

• panel

  • Traditional description for flat, wooden supports used for painting. The term can also refer to more modern supports such as hardboard and Masonite.

• patination

  • The surface finish on bronze sculptures created by applying a chemical solution while heating; foundries jealously guarded patina formulas that were prized by artists.

• paysage

  • See standard-format supports.

• peinture claire

  • A method of including opaque, pale, or white pigments in color mixtures. Also called blonde painting.

• pentimento (pl. pentimenti)

  • A visible trace of a compositional change made by the artist during an artwork’s execution.

• perspective

  • A technique of depicting volumes and spatial relationships on a flat surface. See also atmospheric perspective.

• photomicrograph

  • An image taken through a microscope.

• picture plane

  • The imaginary plane in the image that corresponds to the surface of the picture.

• piece mold

  • A multipart mold used in casting usually plaster, that can be removed from the cast without causing damage to it.

• pigment

  • Colored particles used in artistic media such as oil paint, pastel, chalks, and watercolor.

• plain weave

  • Weave structure where the weft threads are woven over and under every other warp thread reversing the over-under sequence with each subsequent pass of the weft. Also called tabby weave.

• Plasticine

  • A commercial modeling material patented in 1899 formulated to be nondrying and used as an alternative to clay.

• plein air

  • The act of painting or drawing outdoors.

• ply

  • For textiles, this term refers to individual strands twisted together with others to form a thicker continuous strand.

• polarized light microscopy (PLM)

  • This technique uses a light microscope with two polarizing filters (one above and the other below the specimen) to characterize the optical and morphological properties of a specific material. A minute sample is mounted on a glass slide, dispersed in a transparent medium with a known refractive index, and examined in transmitted light. The microscopist studies the color, shape, size, sample homogeneity, refractive index, and other optical phenomena of pigments and fibers and how they interact with light. These observations, when compared to a database of reference materials, allow an experienced analyst to identify the individual pigment or fiber material present in a sample.

• pouncing

  • A method used to transfer an image from one surface to another by puncturing tiny holes in the lines of a drawing and dabbing pounce (usually chalk or charcoal dust) through the pinpricks to create a dotted copy on another support. Pouncing can also refer to the dotted design created on the second surface.

• pre-primed

  • Indicates a canvas that was primed before being cut to size and mounted on a stretcher. The presence of ground extending to the edges of the canvas is indicative of pre-priming. Canvases were sometimes pre-primed by an artist or assistant, but, by the second half of the nineteenth century, more commonly by commercial manufacturers or color merchants who sold pre-primed canvas ready-stretched or in rolls or by the meter for artists to stretch themselves.

• preparatory layer

  • See ground. 

• primary cusping

  • Strong cusping of a textile support that results from stretching before preparation—either by an artist or color merchant stretching an individual canvas before priming or as an effect of larger commercial or industrial preparation of a canvas.

• priming

  • See ground.

• proof

  • An impression pulled from a printing matrix before publication or before the design is completed, in order to evaluate the image.

• quadrillage

  • Definition to come.

• radio opaque

  • A term used to describe materials of high atomic weight (for example, lead white paint), which block X-rays and appear light in X-ray images. See also X-radiography.

• radio transparent

  • A term used to describe materials of low atomic weight (for example, canvas), which are easily penetrated by X-rays and appear darker in X-ray images. See also X-radiography.

• raking light

  • Illumination from an oblique angle used to highlight the topographical features of an artwork.

• Raman microspectroscopy

  • This technique can be used to identify a wide range of materials nondestructively. Using a microscope, spectra can be recorded from samples as small as 1 micron (1 μm = 1/1000 mm) across, and individual pigment particles can be analyzed, either as loose samples or on the surface of cross sections. Visible or invisible laser light is focused through a microscope, and the small portion of light that interacts with the material under study (a phenomenon known as the Raman effect) is scattered back into the microscope onto the detector. This scattered radiation is recorded as a function of wavelength and displayed as a spectrum, a graph in which each particular compound has a characteristic fingerprint. Complementary to FTIR, this technique can characterize inorganic materials such as metal alloys and mineral and synthetic pigments and fillers and some organic compounds, although with organic substances it is sometimes impaired by the fluorescence of the materials under the laser.

• rebate

  • Small margin inside a frame against which a work of art rests. Also called rabbet.

• relining

  • This term can refer to the lining of a painting and also to the act of removing a lining from a painting and lining it again.

• repaint

  • See overpaint.

• reposes

  • The unembellished areas between the carving in center-corner pattern frames. Reposes are sometimes called mirrors, as they are often, if gilded, more light-reflective than the carved parts.

• reserve

  • An area of an artwork left unfinished to be executed later. In practical terms, a figure may be left in reserve while the background of a work is built up, then completed afterward.

• retouching

  • This term is commonly used interchangeably with inpainting; however, it can also refer to overpaint or repaint, generally in reference to a conservator’s intervention. Retouching may also include toning of original paint that has been damaged or abraded.

• roller

  • A printer’s tool made of leather or rubber, ranging from soft to hard, to apply printing ink to a solid matrix such as a wood block, zinc plate, or limestone. In wood-block printing, a soft roller can be used to partially deposit ink into gouged areas while a hard roller can be used to deposit ink only on the high points of the block.

• sand casting

  • A technique of casting bronze sculpture where a piece mold is used to make a version of an artwork in casting sand, a mixture of fine sand and clay, often around a structure of metal rods (an armature). The sand version is then shaved down to create the core of the sculpture, and metal pins are added to hold the core and mold apart while the casting is accomplished. The space between the core and the outer mold is filled with molten metal to make the sculpture. The core material is usually removed after casting, but the rods and pins are often left behind and are visible in X-rays.

• scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX)

  • This technique utilizes electrons, rather than light, to create an image of a sample. It allows for the analysis of very small quantities of materials. The sample is coated with a thin film of carbon or gold, and a small beam of electrons is focused on the sample’s surface. Secondary electrons allow scientists to obtain a three-dimensional image at very high magnification and resolution (up to 100,000×); backscattered electrons (BSE) highlight the distribution of the elements, recording them in different shades of gray according to their atomic weight; and X-ray fluorescence emission allows analysts to determine which elements are present and to infer inorganic (mineral and synthetic) pigments and fillers. The EDX spectrum consists of a graph containing a series of peaks, each one occurring at a precise energy characteristic of a particular element. It is important to note that this technique gives information about what elements are present in a sample but not about their relationships to one another; it also does not indicate the organic compounds (such as binding medium) present. For these reasons, it is best complemented with polarized light microscopy PLM or a molecular fingerprinting technique such as Raman microspectroscopy or FTIR.

• scanning macro X-ray fluorescence spectroscopy (macro-XRF)

  • This technique creates an image of the distribution of specific atomic elements contained in the paint layers of an artwork. An XRF spectrometer is scanned across the area of interest (which may be the entire artwork or only portions of it) and collects XRF spectra for individual spots in successive rows, which are then combined in a single image mapping the distribution of each element in the area examined. These images can be used to formulate hypotheses on the distributions of specific pigments and extenders at or below the surface of the artworks scanned.

• scotia

  • A concave molding that is semicircular in profile; also called a cove.

• scumble

  • An opaque paint layer applied so thinly it appears as a translucent veil over the preexisting layers to soften or dull the appearance. Sometimes a scumble is applied roughly or with a stiff-bristle brush that retains an uneven texture and thickness.

• secondary cusping

  • Cusping related to the stretching of a pre-primed canvas on a stretcher or strainer, usually by either a color merchant or the artist.

• selvage

  • A strip of the woven fabric running along the outer warp threads where the weft changes direction without being cut, thus preventing fraying. There is a selvage at each end of the fabric width. The selvage is often woven differently than the body of the fabric and sometimes includes a colored thread identifying the manufacturer.

• semiglaze

  • A translucent paint layer usually incorporating extra medium and both translucent and opaque pigments.

• sight edge

  • Definition to come.

• sinking in

  • As a paint dries or ages, it may lose its gloss and deep, rich tone unevenly due to absorption of the paint medium by underlying layers.

• size

  • See sizing.

• sizing

  • Material additive or layer, commonly gelatin or glue, added to a support, such as wood, canvas, or paper, to seal it and reduce its ability to absorb paint and other media. In the preparation of canvas, hardboards, and panels, the size is applied before the ground layers. For paper, this material is incorporated internally in the pulp stage or applied to the surface of the formed paper during its manufacture to increase its resistance to water penetration (introduced by ink or watercolor). The process of applying the size layer is called sizing.

• skinning

  • Areas of paper where the fibers have been abraded, or “skinned,” from the surface. The term can also refer to the disruption of a paint surface due to abrasion or solvent action.

• specular light examination

  • Examination of an art object with the illumination angled directly in front of the work in order to maximize specular reflection, or reflection of the light, off the three-dimensional and glossy areas. Images taken under this condition can sometimes show artist changes not readily apparent with other kinds of illumination such as raking light.

• spin

  • For textiles, this term refers to the twisting together fibers of limited length to form a longer continuous strand.

• spun

  • Fibers of limited length twisted together in either a clockwise or counterclockwise direction to form a longer continuous strand within a textile.

• sprue

  • Channels in the mold used to pour molten metal during the casting process.

• standard-size supports

  • See standard-format.

• standard format

  • The range of ready-made commercial supports—canvas, panel, paper, and card—available in an array of fixed sizes that are constant regardless of manufacturer. Standard-size supports are numbered from 1 to 120 and are available in three shapes: portrait (figure), landscape (paysage), and seascape (marine). These three formats have their longer dimension in common, with the short side becoming progressively shorter, so that the portrait format is the closest to being a square, the seascape the narrowest, and the landscape between the two. Some suppliers offered additional variations on select landscape and marine formats, further classifying them as haute (tall) and basse (short). The dimensions of these supports range from 12 to 130 by 22 to 195 cm.

• stereomicroscopic examination

  • Examination of an object with a stereomicroscope, which utilizes reflected light and is designed with two oculars, one corresponding to each eye, to give a three-dimensional visualization of the object at a magnified scale.

• stipple

  • See stippling.

• stippling

  • A painting or drawing technique in which the design is produced by small dots of media arranged to simulate the appearance of volume, light or shade. In printmaking, a similar effect can be achieved by applying ink to a matrix using a hard-bristled brush. Also used in conjunction with stencils.

• strainer

  • A wooden framework with fixed corners used to mount textiles for painting. It is the secondary or auxiliary support for a canvas painting.

• stretcher

  • The wooden framework with expandable joints over which a canvas painting is stretched and attached. It is the secondary or auxiliary support for a canvas painting. Also called a chassis.

• stretcher-bar cracks or creases

  • Paint cracks or canvas creases along the edges of the stretcher members, including the crossbars, from repeated contact between the canvas and stretcher over time.

• strip frame

  • Definiton to come.

• stump

  • See stumping.

• stumping

  • A drawing technique used to blend powdery media in which a piece of soft paper, felt, or leather, rolled to form a point (stump), is held at an angle and rubbed back across the paper surface to transfer the media.

• substrate

  • An inert substance, such as chalk or aluminum hydrate, onto which dyes are precipitated. In the present study, the term is used with regard to lake pigments.

• support

  • The physical surface upon which an artwork is executed. Can include textiles, wood, and other types of board, metal, and paper.

• surface dry

  • A paint layer that is dry to the touch.

• surface-enhanced Raman spectroscopy (SERS)

  • A type of Raman microspectroscopy that requires specific preparation of the sample before analysis. Because of its extremely high sensitivity and its ability to quench fluorescence, it is particularly well suited to the identification of natural organic colorants like those used to make lake pigments. A silver colloid, a suspension of silver nanoparticles obtained by chemical reduction of a silver salt (generally silver nitrate), is typically employed. Prior to analysis, the sample is exposed to hydrofluoric acid vapors in order to increase the absorption of the dye on the metal surface of the silver colloid, thus enhancing the SERS signal. After that, a small drop of the silver colloid is deposited onto the sample and analysis is carried out with a Raman microscope.

• synthetic varnish

  • A type of varnish introduced in the twentieth century that is comprised of a dissolved synthetic polymer.

• tacking edge

  • See tacking margin.

• tacking margin

  • The edges of the textile support that extend over the sides of the stretcher or strainer and by which the support is attached, often with tacks. Also called tacking edge.

• tapping out

  • See keys.

• thread count

  • The number of warp and weft elements in a textile per linear unit of measurement. This can be estimated by localized, manual counting or determined by specially developed automated software. Researchers from the Thread Count Automation Project—including Rick Johnson of Cornell University; Don Johnson of Rice University; and Robert G. Erdmann, Rijksmuseum, Amsterdam, University of Amsterdam, and Radboud University, Nijmegen—use a program that precisely counts the threads in a canvas and maps variations in the weave density from an X-ray. The results can provide information about weaving and priming processes and can be used to identify canvases cut from the same fabric.

• thread-angle map

  • Heat map for the warp and weft threads generated by Thread Count Automation Project software that displays the angles of corresponding threads across the painting. These maps give indications about the weaving and preparation processes and mainly show cusping, both primary and secondary. In addition, weft-angle maps reveal weaving features such as weft snakes and warp-thread repairs.

• thread-count match

  • A statistical agreement between thread-count measurements among two or more canvases in the Thread Count Automation Project.

• thread-density map

  • Heat maps generated by Thread Count Automation Project software that illustrate the deviation of thread counts from the average thread count in the warp or weft direction across an entire painting. Patterns in thread-density maps can be used to determine whether paintings have canvas supports that came from the same bolt of fabric, or bolt matches.

• tide lines

  • A boundary of pigment particles deposited along the edges of a wash or watercolor stroke, often of a darker tone due to a denser accumulation of particles at the boundary edge. Alternatively, tide lines of degradation products in the paper can form at the boundary where a water-damaged area abuts an area of dry, undamaged paper.

• tone

  • Either the relative lightness or darkness of a color (value), or the act of glazing or scumbling for the purpose of changing the color slightly. Toning can sometimes refer to a conservator or restorer’s retouching over abraded original paint.

• torus

  • A convex molding that is semicircular in profile.

• transmitted-infrared imaging

  • This technique is similar to infrared reflectography (IRR), except that the light source is placed behind the canvas, painting, or drawing so that the light is transmitted through it. It has proved especially useful in discovering artists’ changes that are not visible in X-ray or reflected-infrared images, as well as original canvas stamps obscured from view as a result of lining.

• transmitted-light imaging

  • Imaging a work of art, usually with a canvas or paper support, illuminated from behind so that the light passes through the artwork.

• twill weave

  • Weave structure where the weft threads are woven over one or more warp threads then under two or more warp threads in a repeating sequence that is offset with each pass of the weft, creating a characteristic diagonal pattern.

• ultraviolet (UV)

  • Invisible to the naked eye, UV radiation has energies beyond the visible light portion of the electromagnetic spectrum. Materials at the surface of an artwork may exhibit fluorescence in characteristic colors in response to UV radiation, depending on their chemical composition. For example, zinc oxide typically has a greenish-yellow fluorescence when viewed under UV, while certain red lakes often display a pinkish-orange fluorescence. UV-induced fluorescence is visible to the naked eye and can be documented photographically. UV imaging is used to help verify or differentiate surface coatings, pigment composition, and reworkings or restorations and can aid in their identification when coupled with other means of point analysis. UV radiation is also routinely used to study the fluorescence from constituent layers of cross sections under a microscope.

• ultraviolet radiation

  • See ultraviolet.

• underdrawing

  • Compositional sketch drawn usually directly on top of the ground layer in painting or directly onto the paper support in watercolor. Underdrawings can vary in media and level of detail, from simple contours to drawings that are volumetric and heavily detailed.

• underpainting

  • The initial painted layers of a work, which are often subsequently covered. Underpainting can include the initial laying in or blocking in of major compositional forms. Also called ébauche.

• value

  • Value. See toned.

• varnish

  • Resin-based surface coatings on a work of art. Spirit varnishes are made with resins dissolved in a volatile solvent that harden to form a film as the solvents evaporate. These coatings are usually transparent and are intended to protect the surface of a painting from grime and pollution, saturate the colors, and produce a consistent surface gloss.

• vent

  • In the casting process, channels to allow for the escape of gases and excess metal.

• warp thread

  • Fixed longitudinal threads on the loom during the weaving process.

• warp-angle map

  • See thread-angle map.

• warp-thread match

  • Two or more canvases that match in overall thread count (average and distribution) and have thread-density patterns that appear to match in the warp direction. This indicates that the canvases originated from the same bolt (100–200-meter length) of raw canvas. The canvases are aligned laterally on the bolt, but their distance apart cannot be determined. Thread counts and density maps are generated by Thread Count Automation Project software.

• warp-thread repair

  • A starburst-like feature of a weft-angle map—generated by Thread Count Automation Project software—that corresponds to a repair made to the warp thread of a canvas during the weaving process. See also thread-angle map.

• wash

  • Thin paint layer produced by diluting the paint with water or solvent, depending on the binding media. Washes tend to appear more matte and are more liquid than glazes or semiglazes.

• waste mold

  • A two-part mold used to cast a plaster version of a sculpture; the mold is called a "waste mold" because it is destroyed when it is separated from the plaster. This "original" plaster is then used to make a carefully created piece mold or flexible gelatin mold; other plaster versions could be made from these types of mold. From one of the plaster versions yet another mold would have been made, again usually either a piece mold used for sand casting or a gelatin mold for lost-wax casting.

• watermark

  • Formed in paper by attaching wire designs (such as coats of arms, crests, or letters) to the paper mold screen; fewer fibers collect over the wire designs during the sheet formation, resulting in thinner areas visible in transmitted illumination. Watermarks can be studied to learn more about the paper’s date and manufacture.

• wax-resin lining

  • Process of lining a painting using a mixture of wax and natural resin as the adhesive. See also lining.

• weave

  • Woven pattern in textiles created by overlapping warp and weft threads. Common weave patterns include plain, or tabby, weave; twill; and basket weave.

• weave match

  • Two or more canvases which match in overall thread count (average and distribution) and have thread-density patterns that appear to match. Thread counts and density maps are generated by the Thread Count Automation Project software. Also called bolt match.

• weft snake

  • A feature of the weft-angle map—generated by the Thread Count Automation Project software—that appears as a row of weak, cusping-like features away from the edges of the painting and corresponds to a hand-weaving fault. See also thread-angle map.

• weft thread

  • In the weaving process, the weft threads are laterally woven through the fixed warp threads.

• weft-angle map

  • See thread-angle map.

• wet-in-wet

  • The application of wet paint onto a still-wet paint layer; the two paints may be blended or mixed together on the canvas. The presence of wet-in-wet paint application can be used to identify parts of a picture that were painted within a short time frame. Also called wet-into-wet.

• wet-on-wet

  • The application of wet paint onto a still-wet paint layer without mixing or blending the two paints.

• wet-over-dry

  • The application of wet paint onto a paint layer that has already dried or set up. This generally indicates some passage of time between the two applications. Also called wet-on-dry.

• wove paper

  • A type of handmade or machine-made paper formed on a mold screen of finely woven wires lacking the pattern of laid and chain lines. When the paper mold is dipped into water containing a fine dispersion of paper fibers, the fibers settle onto the wire screen as the water drains off; the formed sheet bears the wove wire screen pattern that is most clearly seen when light is transmitted through the paper sheet.

• X-radiography

  • X-radiography involves exposing a painting to X-ray radiation and imaging the transmitted X-rays on film or digitally. Materials vary in their ability to absorb or transmit the radiation, depending on their thickness, density, and chemical composition. X-radiography can reveal changes in composition, artist’s brushwork, damages, and details in the support not visible to the naked eye. Because all of the layers of the painting are superimposed on one plane, the reading of X-ray images (commonly called X-rays) requires careful interpretation.

• X-ray

  • See X-radiography.

• X-ray fluorescence spectroscopy (XRF)

  • This noninvasive means of analysis utilizes a focused beam of X-rays to excite the atoms that constitute the artwork and measure the emitted energy. It provides a characteristic fingerprint of the elements contained in the sampled volume, thus allowing to formulate hypotheses on the artwork's inorganic components (pigments, extenders, metallic elements, and the like, but not binding media or organic pigments). In the case of paintings and works on paper, the sampled volume often includes all painting layers and may also include information about the support.

• Z spun

  • Fibers of limited length twisted together in a counterclockwise direction to form a longer continuous strand.

Click a glossary term on the left to view its definition.