Glossary

abonné A season ticket subscriber, in this case at the ballet or opera.
abrasion A loss of surface material due to rubbing, scraping, frequent touching, or inexpert solvent cleaning.
age cracks The formation of cracks that occur due to a loss of elasticity in the paint film and priming as these materials age, combined with responses to environmental changes (i.e. expansion and contraction of the support).
artist supplier(s) Also called colormen and color merchants. Artist suppliers prepared materials for artists. This tradition dates back to the Medieval period, but the industrialization of the nineteenth century increased their commerce. It was during this time that ready-made paints in tubes, commercially prepared canvases, and standard-format supports were available to artists for sale through these suppliers. It is sometimes possible to identify the supplier from stamps or labels found on the reverse of the artwork (see canvas stamp).
atmospheric perspective An artistic technique used to create the illusion of depth in a composition in which distant elements are cooler and more diffuse, causing them to recede.
blanching A whitish haze or discoloration that may indicate deterioration of a varnish layer or an alteration of the paint film caused by inappropriate cleaning.
canvas stamp An ink stamp, often present on the reverse of the canvas, signifying the company that sold or prepared the canvas. As these companies sometimes performed framing and restorations, these stamps could also reflect these services.
Cloisonnism A style of painting associated with some of the painters who worked at Pont-Aven in Brittany in the 1880s and 1890s. It is characterized by flat forms of bold colors separated by dark outlines. The term is derived from cloisonné, a kind of decorative enamelwork.
cognate In monotypes, cognates are multiple prints pulled from an inked image on a plate. The first print is usually the strongest, and the image quality reduces with each subsequent pull. It is usually possible to pull only two or three prints before the image becomes unreadable. See also monotype.
counterproof (pastel) Pastel paintings can be counterproofed by dampening either the original image or a fresh sheet of paper, and running both through a printing press. The resulting image would be reversed and both images would be lighter in tone.
crayon Traditionally, the French term crayon referred to a wide variety of fabricated, dry drawing media including ground and compressed chalks and pastels. For the purposes of this catalogue, crayon refers to a drawing medium where pigments, dyes, or a mixture of the two are mixed with wax, grease, or oils, or any combination of the three, and compressed into a stick.
cradle A grid-like wooden structure attached to the reverse of a panel by a restorer to prevent warping.
cusping A scalloped pattern along the canvas edges that relates to how the canvas was stretched. Primary cusping reveals where tacks secured the canvas to the support while the ground layer was applied. Secondary cusping can form when a pre-primed canvas is re-stretched by the artist prior to painting.
dark-field monotype A subtractive image creation process where the printing matrix (the nonporous surface onto which the ink is applied) is entirely covered with ink, and the design is created by removing the ink. See also monotype.
deckle edge The edge of a paper sheet that is formed by pulp caught between the deckle, metal or wooden frame, and the papermaking screen. The deckle edge typically has less fiber than the remainder of the sheet and is characterized by a lacy appearance.
delamination The separation of layers in a painting. Examples include separation of the original canvas from the lining canvas, or separation of the paint layer from the ground layer.
drying cracks Also known as traction cracks, these are formed as the paint dries. They are usually the result of a "lean" paint with a small percentage of oil drying faster than an underlying "fat" paint layer with a higher percentage of oil. The quick drying of the top layer causes the paint layer to shrink and crack.
drying oil Drying oils are oils which have the property of forming a solid, elastic substance when exposed to the air. Drying oils that commonly occur in oil paints are linseed, walnut, and poppyseed.
ébauche The first applications of paint that begin to block in color and loosely define the compositional elements. Also called underpainting.
effets French for “effects.” An artist’s emphasis on the atmospheric effects of time and weather on the subject matter.
en plein air (adjective: plein-air) French for "outdoors." The term is used to describe the act of painting quickly outside rather than in a studio.
en pointe A term used in ballet to mean, on the tips of the toes.
etching An intaglio printmaking technique where lines are etched with acid into a metal printing plate. The printing plate is covered with an acid resistant ground, and the artist draws a design into the ground with an etcher’s needle (a sharply pointed stylus). The plate is then immersed in an acid bath, and the metal exposed by the needle is eaten away. After removal of the ground, the plate can be printed by rubbing ink into the etched lines and running the plate and printing paper through an intaglio press.
facture The artist’s characteristic handling of paint.
fermier général French for “general farmer.” A private citizen who collects taxes on behalf of the French monarchy.
fêtes galantes French for “gallant parties.” Paintings that feature elite groups of upper-class men and women shown in conversation, role playing, dancing, or flirting outdoors.
fichu French for “thrown over.” A small triangular shawl, worn around a woman’s shoulders and neck.
fill material A material added to a loss of paint and/or ground to create an area level with the surrounding original paint.
fixative An adhesive or varnish which is applied to the surface of powdery media (pastel, chalk, charcoal, or graphite pencil) to prevent smudging or smearing. Fixatives may be applied during the composition process, so that new layers of media can be added without disturbing the underlayers, or after the artwork is complete. Historic fixatives include natural resins, vegetable gums or starches, animal or fish glues, casein, egg white, and a variety of other materials. In the nineteenth century, cellulose nitrate and other early synthetic polymers were available, and in the twentieth century, acrylics and polyvinyl co-polymers were included in fixative solutions. Until the early twentieth century when methods for containing pressurized gasses were developed and disposable spray cans became common, the fixative could be spattered over the paper with a brush or applied with an atomizer (also called a blow-pipe or mouth sprayer).
Fourier-transform infrared spectroscopy (FTIR) A broadly applicable microanalysis method for the identification of paint media classes such as oils, polysaccharides (gum arabic, etc.), proteins (glue and casein tempera), waxes (medium additions and restoration treatments), resins (varnish components), and synthetic media (restoration acrylics). FTIR is also very important for identifying pigments and fillers, and for differentiating closely-related compounds (e.g. neutral and basic lead carbonates, both of which may be found in lead white).
friable When paint is no longer sufficiently bound. Friable paint often appears powdery or crumbles easily.
glaze A transparent, oil or resin-rich paint application that influences the tonality of the underlying paint.
gouache A term originating in eighteenth century France, which, historically, refers to an opaque paint consisting of colored pigments or dyes, a white opacifying pigment, and a polysaccharide binder, usually gum arabic. Traditional gouache recipes sometimes include honey as a humectant. Although twentieth century and twenty-first century gouache paints are often visually indistinguishable from historic gouache paints, modern gouache paints include a variety of additives that produce a reliably uniform paint in terms of tint and handling properties.
ground layer An opaque preparatory layer applied to the support, either commercially or by the artist, to prevent absorption of the paint into the canvas or panel. See also priming layer.
half basket weave A plain weave produced by double yarns in one direction and a single yarn in the other.
impact cracks A characteristic crack pattern that forms after a blow to a painting. When these appear as circular, spiral, or spider web-like, they are sometimes called sigmoid cracks.
impasto A thick application of paint, often creating texture such as peaks and ridges.
imprimatura A thin layer of paint applied over the ground layer to establish an overall tonality.
infrared (IR) photography A form of infrared imaging that employs the part of the spectrum just beyond the red color to which the human eye is sensitive. This wavelength region, typically between 700-1,000 nanometers, is accessible to commonly available digital cameras if they are modified by removal of an IR blocking filter that is required to render images as the eye sees them. The camera is made selective for the infrared by then blocking the visible light. The resulting image is called a reflected infrared digital photograph. Its value as a painting examination tool derives from the tendency for paint to be more transparent at these longer wavelengths, thereby non-invasively revealing pentimenti, inscriptions, underdrawing lines, and early stages in the execution of a work. The technique has been used extensively for more than a half-century and was formerly accomplished with infrared film.
infrared reflectogram An infrared image captured with an electronic infrared imager, typically in the 1000-2500 nanometer range. See Infrared reflectography.
infrared reflectography (IRR) A form of infrared imaging that exploits the behavior of painting materials at wavelengths beyond those accessible to infrared photography. These advantages sometimes include a continuing increase in the transparency of pigments beyond wavelengths accessible to infrared photography (i.e, beyond 1,000 nanometers), rendering underdrawing more clearly. The resulting image is called an infrared reflectogram. Devices that came into common use in the 1980s such as the infrared vidicon effectively revealed these features but suffered from lack of sharpness and uneven response. Vidicons continue to be used out to 2,200 nanometers but several newer pixelated detectors including indium gallium arsenide and indium antimonide array detectors offer improvements. All of these devices are optimally used with filters constraining their response to those parts of the infrared spectrum that reveal the most within the constraints of the palette used for a given painting. They can be used for transmitted light imaging as well as in reflection.
laid paper One of the two types of paper. Laid papers are machine or handmade papers, formed on a screen with parallel and tightly spaced wires that form "laid lines" which are visible on the sheet. The laid wires are held together by more widely spaced wires called "chain" lines. In handmade papermaking, the chain wires also secured the screen to the ribs of a wooden frame (the frame and wire assembly is referred to as a mold) that was dipped into a vat of paper-making fibers. In the late eighteenth century, there were widespread changes in the laid mold structure, and papers produced prior to this time are distinguishable by an accumulation of fibers along the chain lines. The other type of paper is wove paper.
lining A procedure used to reinforce a weakened canvas that involves adhering a second fabric support using adhesive, most often a glue-paste mixture, wax, or synthetic adhesive.
lithography Invented by Alois Senefelder (German, 1771–1834) in the late eighteenth century, lithography is a planographic printmaking technique. The name (literally: stone drawing) comes from the use of a stone as the printing matrix; however, grained aluminum and metal plates are also used. Preparation and printing of the images is a based on the hydrophobic nature of grease. The design is drawn with greasy crayons or an oily ink called tusche. The stone is then synthesized so that printing can be accomplished by first wetting the stone (the water is repelled by the grease in the media) and then inking the stone with a greasy ink (the ink adheres grease in the crayon and tusche). The image is transferred to the paper with a press that exerts tremendous pressure on the stone. Like other printing techniques the printed image reverses the image on the stone. There is no platemark as seen in monotypes; instead the area of contact between the stone and the paper will have a flatter appearance than the surrounding paper.
marine Term used to describe a variety of painted sea subjects, including beach scenes, vistas of the open sea, and shipwrecks or portraits of ships.
mechanical cracks Cracks, either localized or overall, that form in response to movement or stress.
monotype A type of planographic print where a design is drawn or painted on a non-porous surface, such as a printing plate or glass, and the design is transferred, in reverse, to paper by manual pressure, or pressure from a printing press. The monotype process produces unique prints because the ink is depleted each time paper comes in contact with the matrix. The first print is the strongest in terms of tone and contrast, and the quality decreases with each subsequent print. (See also dark-field monotype and cognate).
Orientalist An art-historical term for subject matter depicting the Near East by western artists, primarily in the nineteenth century.
overpaint Restoration paint that covers original paint that may or may not be damaged. Historically, overpaint has often been applied too broadly, altering the intended aesthetic of the painting and sometimes introducing conceptions foreign to the original artist, thereby altering our understanding of the work and the era to which it belongs.
pastel A type of drawing stick made from finely ground pigments or other colorants (dyes), fillers (often ground chalk), and a small amount of a polysaccharide binder (gum arabic or gum tragacanth). While many artists made their own pastels, during the nineteenth century, pastels were sold as sticks, pointed sticks encased in tightly wound paper wrappers, or as wood encased pencils. Pastels can be applied dry, dampened, or wet, and they can be manipulated with a variety of tools including paper stumps, chamois cloth, brushes, or fingers. Pastel can also be ground and applied as a powder, or mixed with water to form a paste. Pastel is a friable media, meaning that it is powdery or crumbles easily. To overcome this difficulty, artists have used a variety of fixatives to prevent image loss.
pastorals A genre of painting that portrays rural life, especially the lives of shepherds, in an idealizing way. Such works represent the courtier’s or city-dweller’s dream of escape.
peinture à l’essence De-oiled paint. Peinture à l’essence was produced by the artist by leaching much of the linseed oil out of commercial paints and mixing the resulting thickened paint with turpentine. The resulting paint could be applied as a wash and dried more quickly than unmodified paint.
pentimento (pl: pentimenti) A change to the composition made by the artist that is visible on the paint surface. Often with time, pentimenti become more visible as the upper layers of paint become more transparent with age. Italian for "repentance" or "a change of mind."
photomicrograph An image captured using a microscope.
picture plane The two-dimensional surface where the artist applies paint.
plain weave A basic textile weave in which one weft thread alternates over and under the warp threads. Often this structure consists of one thread in each direction, but threads can be doubled (basket weave) or tripled to create more complex plain weave. Plain weave is sometimes called tabby weave.
platemark A depression in a sheet of paper caused by the edge of a printing plate. The platemark is the product of the pressure exerted by the printing press onto both the plate and the paper.
polarized light microscopy (PLM) A method used for the study and differentiation of pigments based on the optical properties of individual particles, including color, refractive index, birefringence, etc. PLM is particularly useful in identifying the presence of organic pigments such as indigo and Prussian blue, which often cannot be differentiated from paint medium in the scanning electron microscopy (SEM); differentiating synthetic pigments from their natural analogs by particle shape or the presence of extraneous mineral matter; and disclosing the presence of pigments with similar composition but differing color, such as red and yellow iron oxides.
polyvinyl acetate A thermoplastic resin created by polymerizing vinyl acetate. White in color and tacky when wet, it dries to form a clear, tough film. Polyvinyl acetate is used widely in emulsions for paints and adhesives. Also noted as PVAc, PVAC, or (less inaccurately) as PVA.
priming layer An opaque preparatory layer applied to the support, either commercially or by the artist, to prevent absorption of the paint into the canvas or panel. See also ground layer.
profil perdu French for "lost profile." The artist shows their subject without the profile of the head being visible. A profile of a human head that is not seen directly from the side, but more from the back of the head.
raking light An examination technique in which light is placed at a shallow angle from one direction to reveal the surface topography.
Raman spectroscopy A microanalytical technique applicable primarily to pigments and minerals, differentiating them based on both chemical bonding and crystal structure, often with extremely high sensitivity for individual particles. For example, traditional indigo and synthetic phthalocyanine blue are both carbon compounds not well differentiated by other methods utilized here, especially when used dilutely. However, they give unique Raman spectra. Calcium carbonates derived from chalk or pulverized oyster shell of identical chemical compositions can be differentiated based on their crystal structures (calcite and aragonite, respectively).
reflected infrared digital photograph An infrared image produced in the 700–1000 nanometer range, typically captured using an infrared-modified digital camera. See infrared photography.
Reflected light microscopy (of cross-sections) A procedure used in limited cases with microsamples to determine the layering of paint applications and thereby resolve pigments into successive layers of application. Samples are embedded in mounting resin under vacuum, cured at 60 degrees Celsius, ground, and polished to a one-micron finish. Thereafter they are examined using the reflected light microscope, ultraviolet fluorescence microscope, and scanning electron microscope.
repoussoir An object, motif, or figure placed on the right or left foreground of a painting used to direct the viewer’s eye into the composition and increase the illusion of depth.
reserve An area of the composition left unpainted with the intention of inserting a feature at a later stage in the painting process.
retouching Paint application by a conservator or restorer to cover losses and unify the original composition. Retouching is an aspect of conservation treatment that is aesthetic in nature and that differs from more limited procedures undertaken solely to stabilize original material. Sometimes referred to as inpainting or retouch.
Salon, the Exhibitions organized by the French Royal Academy of Painting and Sculpture (Académie Royale de Peinture et de Sculpture) and its successor the Academy of Fine Arts (Académie des Beaux Arts), which took place in Paris from 1667 onwards.
scanning electron microscopy (SEM) Performed on a microsample of paint, the SEM provides a means of studying particle shapes beyond the magnification limits of the light microscope. This becomes increasingly important with the painting materials introduced in the early modern era, which are finer and more diverse than traditional artists’ materials. The SEM is routinely used in conjunction with an X-ray spectrometer, so that elemental identifications can be made selectively on the same minute scale as the electron beam producing the images. SEM methods are particularly valuable in studying unstable pigments, adverse interactions between incompatible pigments, and interactions between pigments and surrounding paint medium, all of which can have profound effects on the appearance of a painting.
scumble A thin layer of opaque or semi-opaque paint that partially covers and modifies the underlying paint.
simultaneous contrast Simultaneous contrast is the interaction of two colors when placed side by side. Depending on the colors, the viewer’s perception of the color will change. For example, blue will cause red to appear orange, and red causes blue to appear green. Complementary colors (colors that are opposite each other in a color wheel, such as red and green, blue and orange, or yellow and purple) produce most striking simultaneous contrast. While simultaneous contrast was formulated by the French chemist Michel Eugène Chevreul (1786–1889) in his treatise The Principles of Harmony and Contrast of Colors, and Their Applications to the Arts (1839), the use of simultaneous contrast in painting predates the treatise by more than 100 years.
sizing layer A dilute glue layer, usually animal-based protein such as hide glue, applied to a canvas prior to the ground and paint layers. Its purpose is to shrink the canvas before use and to act as a sealant, protecting the canvas from degradation of acidic materials, such as oils. The glue material is often called size, while the process is called sizing.
sous-bois French for ”undergrowth“ A genre of paintings of the forest floor made popular by the Barbizon painters from the 1830s to about 1870.
specular illumination an examination technique in which light is reflected off an artwork’s surface in order to better visualize sheen variation, surface textures, and surface anomalies.
staffage Small figures or animals used to enliven a landscape or architectural painting.
standard-format supports Commercially prepared supports available through art suppliers, which gained popularity in the nineteenth century during the industrialization of art materials. Available in three formats figure (portrait), paysage (landscape), and marine (marine), these were numbered 1 through 120 to indicate their size. For each numbered size, marine and paysage had two options available: a larger format (haute) and smaller (basse) format.
stereographic photography Twin images that, when viewed together through a special device, produce an illusion of three-dimensionality.
stretcher A wooden structure to which the painting’s canvas is attached. Stretchers can be expanded slightly at the joints to improve canvas tension and avoid sagging due to humidity changes or aging.
stretcher cracks Linear cracks or deformations in the painting’s surface that correspond to the inner edges of the underlying stretcher or strainer members.
strip lining A conservation technique used to strengthen/repair tacking margins that have weakened or failed. New fabric is adhered to the painting’s damaged tacking margins to allow the stretcher to exert its normal tensioning on the original canvas.
stumping Blending, removing, lightening, or softening stokes of powdery media (pastel, charcoal, chalk, or graphite pencil) with a stump or tortillon. The stump is made from paper, leather or thin felt, which is rolled so that it forms a point. If blending is the main object of stumping, then the technique is referred to as stump blending to differentiate between blending with fingers, a brush, or chamois skin.
sur le motif French for "in front of the object." A term used for sketching or painting from life.
Synchrotron X-ray fluorescence spectrometry elemental mapping or synchrotron MA-XRF The synchrotron is essentially a vastly brighter and more localized source of X-rays substituted for an X-ray tube. A unique trait of the synchrotron, not shared with X-ray tube sources, is the ability to tune all of its X-ray energy to a single level at which absorption by an overlying lead layer is minimized, thereby partially overcoming the shielding effect of upper layers of paint. The Maia X-ray detector offers an array of 384 individual detector elements capable of simultaneously measuring the torrent of characteristic fluorescent X-rays produced by the pigments under illumination of the synchrotron source. These 384 components surround the synchrotron beam and collect the characteristic fluorescent X-rays of the pigments from each point on the painting as it is swept past the beam and detector.
tacking edge The outer edges of canvas that wrap around and are attached to the stretcher or strainer with tacks or staples. See also tacking margin.
tacking margins The outer edges of canvas that wrap around and are attached to the stretcher or strainer with tacks or staples. See also tacking edge.
turnover edge The junction between the picture plane and the tacking margins.
traction cracks Also known as drying cracks, these are formed as the paint dries. They are usually the result of a “lean” paint with a small percentage of oil drying faster than an underlying “fat” paint layer with a higher percentage of oil. The quick drying of the top layer causes the paint layer to shrink and crack.
transfer lithography Although transfer lithography was introduced in Alois Senefelder’s (German, 1771–1834) treatise on lithography in the late eighteenth century, it was not until the lithography revival of the late nineteenth century that the technique caught on. Transfer lithography involves drawing on a prepared paper with lithographic crayons and tusche (an oily ink). The paper is then laid face down on the stone, wetted with water and solvents such as turpentine, and passed through the press. The image transferred to the stone, and could be processed, inked, and printed. The resulting prints resembled the original drawing in orientation (the image was not reversed) and media application. The original drawing was usually destroyed during transfer process. See also lithography.
transmitted light An examination technique in which light is projected through the painting to examine the painting substrate or to reveal variations in paint application.
twill weave A canvas weave in which one weft thread passes over one or more warp threads before passing under two or more warp threads, creating a pronounced diagonal pattern.
ultraviolet (UV) fluorescence or UV-induced visible fluorescence A non-destructive examination technique whereby the visible fluorescence produced when a painting is illuminated with UV radiation is used to differentiate original paint from restored passages or to characterize the varnish layers. Some pigments exhibit strong UV-induced visible fluorescence, allowing their distribution to be seen across the composition.
ultraviolet radiation (UV) A segment of the electromagnetic spectrum, just beyond the sensitivity of the human eye, with wavelengths ranging from 100-400 nanometers. For a description of its use in the study of art objects, see ultraviolet (UV) fluorescence or UV-induced visible fluorescence.
Ultraviolet-induced visible light fluorescence microscopy (of cross sections) A method used in limited cases with microsamples to determine the layering of paint applications. Differences in both pigmentation and formulation of the paint medium will influence the UV fluorescence behavior of the paint layers.
underdrawing A drawn or painted sketch beneath the paint layer. The underdrawing can be made from dry materials, such as graphite or charcoal, or wet materials, such as ink or paint.
underpainting The first applications of paint that begin to block in color and loosely define the compositional elements. Also called ébauche.
wash An application of thin paint that has been diluted with solvent.
watermark An identifying mark in a paper sheet which is created by tying wires to the papermaking mold. Watermarks are most easily viewed with transmitted light; however, some can be read with raking light.
weave interference A distortion that can occur when excess heat or pressure is applied to a painting, usually during the lining process. As a result, the original canvas weave texture becomes more pronounced or the weave texture of the lining material becomes visible on the painting surface. Also called weave emphasis or weave accentuation.
wet-into-wet An oil painting technique which involves blending of colors on the picture surface.
wet-over-dry An oil painting technique that involves layering paint over an already dried layer, resulting in no intermixing of paint or disruption to the lower paint strokes.
wet-over-wet An oil painting technique which involves drawing a stroke of one color across the wet paint of another color.
wove paper One of the two types of paper. Wove papers may be either machine or handmade, and are produced from molds that have a woven wire mesh. The weave of the mesh can be so tight that it produces no visible pattern within the paper sheet, and often wove papers have a smoother surface than laid papers. Wove papers were developed during the mid-eighteenth century, but did not come into widespread use until later. The other type of paper is laid paper.
X-ray fluorescence spectrometry elemental mapping (MA-XRF) or XRF elemental mapping A non-destructive technique that entails collecting thousands of X-ray fluorescence spectra at regular intervals across a painting to build an alternate set of images depicting the locations and amounts of different elements. Although the information is fundamentally the same as measurements gathered from a single-point XRF, the graphical nature of the result is often a more powerful technique for understanding trends in an artist’s use of materials. The high number of spectra allows statistical manipulations of the elemental information to locate correlations between different pigments that would not be possible from a small number of tests. For example, the consistent occurrence of mercury along with chromium, and iron along with copper, could show that vermilion was used to mute the chrome green and red ocher was similarly employed in a mixture that includes emerald green. The resulting correlation maps then serve to show where the two cases occur in the composition. MA-XRF can also reveal preliminary paint applications that became covered as the composition was completed, thereby disclosing aspects of the painter’s method.
X-ray radiography (also referred to as x-radiography or radiography) Radiography is an examination tool analogous to the use of X-rays in medicine whereby denser components of a painted composition can be recorded as an inverted shadow image cast on film or a digital X-ray imaging plate from a source such as an X-ray tube. The method has been used for more than a century and is most effective with dense pigments incorporating metallic elements such as lead or zinc. It can reveal artist changes, underlying compositions, and information concerning the artwork’s construction and condition. The resulting image is called an x-radiograph or radiograph. It differs from the uses of X-ray spectrometry in being dependent on the density of the paint to absorb X-rays before they reach the film or image plate and being non-specific as to which elements are responsible for the resulting shadow image.
doi: 10.37764/78973.2.1010