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Acknowledgments
About This Glossary
cartouche
cross-sectional analysis
crossbar
Fourier transform infrared microspectroscopy (FTIR)
glaze
infrared reflectography
scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX)
sizing
specular light examination
strainer
stretcher
tacking margin
transmitted-infrared imaging
ultraviolet (UV)
underdrawing
X-radiography
X-ray
X-ray fluorescence spectroscopy (XRF)
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).
cartouche
A decorative enclosure resembling a shield or scroll, often with boundaries of c-scrolls or scrolled foliage.
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.
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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.
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.
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.
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.
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.
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 or surface coatings not readily apparent with other kinds of illumination such as raking light.
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.
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.
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.
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.
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.
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.
Click a glossary term on the left to view its definition.