A gradual loss of material caused by rubbing, wearing, or scraping. Abrasion can be caused by weathering or handling, or by deliberate attempts to smooth the material. Abrasion can also occur during cleaning, particularly with varnish removal, a result historically of using inappropriate solvent combinations and/or mechanical action from a swab or other device. (Adapted from National Gallery of Art online glossary
A substance, in the form of a liquid, paste, powder, or dry film, used to hold materials together by a surface attachment. Properties include solubility, tackiness, bonding time, and bonding strength. Adhesives are most commonly activated by water, solvents, pressure, or heat. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
The brand name for a thermoplastic polyvinyl acetate resin. Characterized by its low molecular weight of about 12,800. Most generally used as an additive to other polyvinyl acetate resins to lower their softening point. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
a raised lip along the edge of a picture plan where the ground once extended onto an engaged frame that was later removed.
A piece of wood that is used as crosspiece to secure the joint between two parallel boards. Frequently found as a structural support on the backs of paintings or altarpieces. (Adapted from Getty Art & Architecture Thesaurus Online
A lightened or white appearance in a paint or varnish layer. Unlike bloom, which is a surface phenomenon, blanching is due to microscopic disruptions that develop within a paint or varnish layer as it ages. These disruptions scatter light making the affected area appear lightener than the surrounding areas. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
A hazy or cloudy appearance to the surface of a painting resulting from the deposition of atmospheric pollutants, or, in the varnish layer, trapped or condensed moisture. A type of bloom can also occur in the paint layer when organic salts, formed by a reaction between pigments and oily components in the binder, migrate to the surface. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
A material used as an underlying layer for gold leaf that is composed of natural red clay processed with water and hide glue. Its color contributes to the appearance of the gold leaf and its smooth texture provides a dense surface for burnishing. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
A variant of the mortise and tenon joint in which the mortise is made with three open sides and both mortise and tenon are cut to the full width of the tenon member. (Adapted from AIC WIKI Stretchers and Strainers: Glossary
A full-scale preliminary design for a painting or tapestry.
Ornamental stalks rising between the leaves of a Corinthian capital, from which the volutes spring and upon which the fleurons are sometimes supported. (Adapted from Getty Art & Architecture Thesaurus Online
(It. “light-dark) A painting technique adapted from CAMEO).rom CAMEO).acute angle on val, g cleaning, a result of using inappropriate solvent combinations and/or mechwhere form is dramatically modelled by almost imperceptible gradations of light and dark. (Adapted from Tate Art Terms Glossary
A wooden grid applied to the reverse of a panel. Cradles were frequently applied in the nineteenth and early twentieth centuries to prevent the panel's warping. In some cases, this was successful, but in many others, cradles restricted the panel's movement and caused splits to form in the original support. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
Irregular, hairline cracks that may occur in a paint layer or varnish coating. Microscopic cracks produce a white, hazy appearance. Crazing may occur due to non-uniform shrinkage on drying or cooling, stress on the object, inherent defects in the material, or as the film becomes brittle (such as the case with varnish). (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
A tiny sample taken from an area of a painting used to study the layer structure of the materials present. The sample is taken along the painting plane, embedded in resin, and polished orthogonally to the layers of interest to reveal the layer structure. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
Distortions along the edges of a canvas caused by tension from the nails or tacks that attach it to the stretcher or strainer. This tension forms a characteristic undulation that is also referred to as scalloping. (Adapted from National Gallery of Art online glossary
A monochromatic underpainting over which subsequent paint layers are applied.
An analytical method for dating wood using the number and width of annual growth rings. Variations in the width of a tree's growth rings indicate yearly climatic conditions for its local growing region. Measuring 50 to 100 years of growth rings produces a pattern that can be compared with master charts to determine a tree's active growing years. This information can thus be used to determine the felling date of trees that were used to make panel paintings.
An interlocking joint between the two pieces of wood in which a flaring mortise and a flared tenon are fit together. The sides are beveled in both the receiving mortise and the tenon. The bevels are away from the exterior of the mortise, creating a lip that helps secure the tenon in the mortise slot. (Adapted from AIC WIKI Stretchers and Strainers: Glossary
Frames that are physically one with the panels they surround, thus serving both a structural the aesthetic function. They sometimes serve to connect numerous panels in a larger structure, such as in an altarpiece. (Adapted from Getty Art & Architecture Thesaurus Online
Layers of tissue or paper applied to a paint surface with an adhesive to create a protective barrier.
On paintings, a material usually used to fill a loss in the paint and/or ground layer and provides a surface for inpainting. Fill materials are often composed of chalk or gypsum mixed with adhesive and are sometimes textured or colored.
A decorative floral motif, square in shape, that can be used for decorative borders and to embellish frames. (Adapted from Oxford Reference
Gamblin Conservation Colors
The brand name for premixed conservation paints containing pigments combined with the low molecular weight aldehyde resin, Laropal A-81. Frequently used by conservators for inpainting.
Traditionally, a mixture of gypsum (calcium sulfate) and animal glue used as a ground for tempera, for some types of oil painting and gilding, and for modelled decoration on furniture and picture frames. Since the late twentieth century, the term “gesso” has been used to refer to commercial canvas primers formulated by synthetic binders and with white pigments such as chalk, zinc oxide, and/or titanium dioxide. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
An initial preparation layer, found primarily on early Italian panel paintings, containing coarse particles of anhydrous calcium sulfate mixed with glue. This initial preparation layer was covered with the more finely ground gesso sottile (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
A final preparation layer, found primarily on early Italian panel paintings, containing fine particles of calcium sulfate dihydrate mixed with glue. Gesso sottile was prepared from the fine particles of suspended gypsum found after soaking the material in excess water. It provided a smooth surface over the coarser gesso grosso layer. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
A transparent paint layer that is composed of a high medium-to-pigment ratio. It is frequently applied over opaque layers of paint to alter their tonality.
A series of closely spaced parallel lines, used in drawing, engraving, and egg tempera painting, to render a uniform color or shadow. In crosshatching, two sets of lines are used, placed across one another, usually at right angles.
Application of paint in thick, highly textured, opaque masses using a brush or palette knife. Marks from the implement of application are often evident. (Adapted from Getty Art & Architecture Thesaurus Online
A thin, even layer of paint that is applied over the ground layer. The imprimatura is used to seal the porous ground and/or create a colored priming layer used to establish tonality. (Adapted from National Gallery of Art online glossary
Lines created by scratching into a ground, imprimatura, or paint layer.
The application of restoration paint solely to areas of lost original paint. Inpainting is applied over an isolating layer, such as a varnish, and is easily reversible. This process aims to visually integrate areas of loss by mimicking the original while carefully adhering to ethical standards for conservation practice. (Adapted from National Gallery of Art online glossary
Laid and chain paper
A type of paper made on a paper mold where paper pulp is placed on a grid of wires. Horizontal wires, known as laid lines, are arranged in rows. Vertical wires, known as chain lines, are more widely spaced and are made of a thicker wire. The pulp sheet that is formed reveals a pattern due to differences in pulp thickness caused when the suction of the water pulls the wet pulp against the wires of different thickness
Metallic salts formed from long-chain organic acids and lead ions. Examples include lead stearate, lead linoleate, lead oleate, and lead naphthenate. Lead soaps commonly appear as microscopic white inclusions in a paint film. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
Lefranc and Bourgeois Couleurs Pour La Restauration
(name changed to Charbonnel Restoration Colors) A brand name for a series of paints that used a mixture of acrylic and ketonic resins. They are non-yellowing, permanently flexible, strongly pigmented, highly light-fast, and characterized by a consistency that is similar to oil paint. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
(also relining) The adhesion of a second piece of fabric to the back of a painting's original support. Lining canvases have been adhered using materials such as glue-paste, wax-resin, and, in modern times, BEVA®371. Linings are usually added to physically reinforce a weak or damaged canvas, but they have been used historically for other reasons, including to flatten the surface of a painting. (Adapted from National Gallery of Art online glossary
A drying oil used in artist paints that is made from the seeds of the common flax plant (Linum usitatissimum
) and produces a hard film when dry. Linseed oil contains a range of fatty acids in the following percentages: linolenic (48–60%), oleic (14–24%), linoleic (14–19%), palmitic (6–7%), and stearic (3–6%). (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
The process of adhering a support to a rigid substrate. It is most often used in painting conservation to refer to the adhesion of a canvas or thinned panel to a rigid support such as wood or metal.
A material made from a mixture of linseed oil and mastic resin that produces a gel-like medium with good working properties. However, its aging properties are poor, and surfaces containing megilp frequently become cracked, blistered, and discolored with age. Megilp was most widely used as a painting medium in the eighteenth and nineteenth centuries. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
A joint between two boards, frequently stretcher or strainer members, meeting at an angle in which each of the abutting surfaces is cut to an angle, usually 45°, equal to half the angle of the junction, usually 90°. (Adapted from AIC WIKI Stretchers and Strainers: Glossary
A gilding process in which gold leaf (usually shell gold) is sprinkled over a thin layer of mordant, usually composed of drying oil sometimes mixed with a pigment such as lead white. Oil gilding was used for small areas of paintings such as halos and gold detailing on the robes of figures. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
(commonly DMF) An organic solvent with the formula (CH₃)₂NCH. It is a colorless liquid that is miscible with water and most organic liquids. (Adapted from Wikipedia: Dimethylformamide
The volatile and flammable components in petroleum. Naphtha contains both aliphatic and aromatic hydrocarbons. It is also used as the common name given to smaller portions of this hydrocarbon distillate mixture. Naphtha is used as a solvent to remove oil and grease. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
The brand name for a thermoplastic acrylic resin composed of a copolymer of ethyl methacrylate and methyl acrylate. It is frequently used as a synthetic varnish, retouching medium, and adhesive in painting conservation. Produced by Rohm and Haas (previously called Acryloid B-72 in the United States). (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
The brand name for a copolymer of methyl methacrylate and ethyl acrylate. It is used as an all-purpose coating material in art conservation. Produced by Rohm and Haas (previously called Acryloid B-82 in the United States). (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
A paint structure in which a greater amount of medium than pigment is proportionately present.
A textile weave pattern made by passing weft threads over and under alternating warp threads. The adjacent weft thread reverses the pattern by going under, then over, opposite warp threads. The thickness of the weft and warp threads are the same on a plain weave textile. Plain weave textiles can be tightly or loosely woven. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
A transfer technique in which small holes are punched in a cartoon. The cartoon is then placed on the painting support and dusted with charcoal (or pigment) to transfer the image to a painting surface.
(Also quartersawn) A cut of wood that follows the longitudinal grain of a tree and is perpendicular to the growth rings, causing the growth rings to appear as parallel lines along the end of the plank. This cut of wood is the most resistant to warp, due to the evenly spaced growth ring pattern, and therefore the most valuable to artists. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
A material that blocks X-rays from penetration and thus appears white in an X-radiograph.
A pattern created by the ray cells (or ray parenchyma) when cut in cross-section. Unlike most cells in the tree, which run vertically up and down the tree, these cells run horizontally and primarily store starches and sugars. This pattern is visible on many species of wood when boards are radially cut. (Adapted from Gene Wengert, “Looking at Ray Fleck,” FDMC Magazine, 23 March 2011
An object or figure placed in the right or left foreground of a composition whose purpose is to direct the viewer’s eye into the picture.
A defined area of a painting, generally corresponding to the area within the outermost contour of an object that is a central feature of the composition, which is left temporarily unfinished or blank while the surrounding areas are partially or fully completed. (Adapted from Essential Vermeer 3.0 glossary
Actions aimed at facilitating appreciation, understanding, and use of an object when the item has lost part of its significance or function through past alteration or deterioration. Most often such actions modify the appearance of the item. Often used to refer to interventions taken to address aesthetic concerns without strict adherence to the modern ethical guidelines of conservation practice. (Adapted from ICOM-CC terminology for conservation
Application of restoration paint to areas of loss to visually integrate them with the color and pattern of the original. Used in this catalogue to refer to restorations done without strict adherence to the modern ethical guidelines of conservation practice (see inpainting). (Adapted from National Gallery of Art online glossary
A style marked by exuberant decoration often modeled on nature, with an abundance of curves, counter-curves, and undulations. It originated in France in the first half of the eighteenth century during the reign of King Louis XV. (Adapted from Wikipedia: Rocaille
The edges of a canvas that run parallel to the warp threads and are created by the weft threads looping around the final warp threads at the end of each row. The presence of both selvages, therefore, indicate the full width of the canvas. (adapted from Wikipedia “Selvage
A technique in which the surface of a paint layer is scratched to reveal a different color or material in an underlying layer. This technique was often used on early Italian panel paintings where a pigment layer was applied over a gilded surface. Patterns were scratched to reveal the underlying gold, creating the effect of gold brocade among other decorative motifs. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
A coating material that creates a smooth finish and a high polish. It is produced a resinous substance excreted by the female lac insect. The resin is placed in alcohol to produce a product that is durable but not completely water-repellent. (Adapted from Getty Art & Architecture Thesaurus Online
A crack pattern that creates a spider-web or bull’s-eye shape radiating out from a single point. It is often the result of impact to the paint surface.
Glue. Frequently used to refer to a layer applied directly to a panel support before the application of the ground, or between layers of ground, as part of the painting preparation process.
(Fabric) A soft lump or irregularity in a yarn of canvas causing a slight inconsistency in the weave pattern.
Ground blue potassium glass containing small amounts of cobalt oxide, primarily used as a pigment from the fifteenth through the eighteenth century. In Europe, the use of smalt was widespread as early as the late sixteenth century because of its low cost. Its manufacture became a specialty in the Netherlands and Flanders in the seventeenth century. (Adapted from Pigments through the Ages
A triangular space found between the top of an arch and a rectangular frame, frequently a space filled with decorative elements. (Adapted from Wikipedia “Spandrel”
The edge of a canvas that attaches to the stretcher or strainer. The tacking margin is wrapped around the side of the stretcher or strainer and tacked or stapled to the wood. (Adapted from National Gallery of Art online glossary
(also referred to as plain sawn or flat sawn) A cut of wood that follows the longitudinal grain of a tree and runs tangentially to the center of the log so that the annular rings are 45° (or less) to the face of the board. This cut of wood is the most readily available but is less resistant to warp than radially cut wood due to the angle of growth rings.
A circular painting. Though created since Greek antiquity, the tondo developed as an independent form in Florence in the first half of the fifteenth century and was produced primarily for domestic settings. The Adoration of the Magi and the Virgin and Child were particularly popular subjects. (Adapted from National Gallery of Art online glossary
Surface markings, in the case of paintings usually on the verso of a wood or copper panel, that were created by the tool that was used to thin and smooth the wood or work the copper flat.
(also alligator craquelure or alligatoring) A pattern of drying crack that is created when an upper layer of paint dries more rapidly than the underlying layers producing a pattern of islands where gaps are wide and disfiguring, often resembling alligator scales. (Adapted from Getty Art & Architecture Thesaurus Online
Inpainting technique in which loss compensation is carried out in short, vertical strokes, resulting in inpainting that is, on close inspection, distinguishable with the naked eye but difficult to notice at a normal viewing distance. (Adapted from Getty Art & Architecture Thesaurus Online
Turbid medium effect
Created when a light color is painted over a darker tone resulting in a cooler appearance than if the same light color was painted over a lighter tone (Adapted from Essential Vermeer 3.0 glossary
A textile weave pattern produced by passing the weft threads over one and under two, or more, threads of the warp. Characterized by parallel diagonal ridges or ribs, the weave may be varied by changing the angle or direction of the twill line, as exemplified in herringbone twill. (Adapted from Getty Art & Architecture Thesaurus Online
A preparatory drawing applied to a prepared support, usually over the ground layer, intended to guide the paint application.
A preliminary paint layer in which composition and tonal values are established. Also used to refer to an area in which an opaque area of paint is applied under translucent glaze layers. (Adapted from Getty Art & Architecture Thesaurus Online
A final coating applied to the surface of a painting to saturate the color, protect the surface, create a uniform gloss, or isolate an original paint layer from conservation interventions such as inpainting. Varnishes can be composed of natural resins, such as mastic, damar, or copal, or synthetic resins, such as Paraloid B-72, Laropal A81, or MS2A.
Vehicular paint structure
A paint composed of a relatively balanced ratio of pigment to medium.
Thin facing sheets intended to be adhered to the surface of an inferior material to enhance its decorative properties. Common veneer materials include wood, plaster, ivory, tortoiseshell, or thin metal. (Adapted from Getty Art & Architecture Thesaurus Online
A layer of paint, usually composed of green earth, which is applied under skin tones to create areas of shadow. Most frequently used to refer to the technique commonly found in late medieval and early Renaissance Italian paintings.
The spiral forms found in capitals of the Ionic, Corinthian, and Composite orders. Also used for other three-dimensional scrolling elements in architecture and the decorative arts such as frames. (Adapted from Getty Art & Architecture Thesaurus Online
The threads that are positioned lengthwise in the loom and run parallel to the selvage in a woven textile. They are usually twisted more tightly than the weft threads. (Adapted from Getty Art & Architecture Thesaurus Online
A technique of applying gold leaf. The surface is typically prepared with a ground layer followed by a bole layer. Once dry, the bole layer is moistened with water or alcohol and glue is applied. Gold leaf is then applied to the prepared bole. Capillary action draws the water into the bole and holds the gold leaf in place as the bole dries. After drying, the gold is burnished to a bright, shiny finish. (Adapted from Conservation and Art Materials Encyclopedia Online [CAMEO]
A surface texture created during the lining process by which the canvas weave of the lining canvas is superimposed on the canvas weave of the original canvas.
A painting technique in which wet paint is applied over underlying layers of wet paint, frequently resulting in the blending or merging of colors.
A painting technique in which wet paint is applied after underlying layers of paint that have dried.
(Ger. “wonder chamber”) Assemblage of art objects and curiosities collected in the sixteenth and seventeenth centuries primarily by European rulers, aristocrats, and early practitioners of science. These collections were in some ways the forerunners of modern museums.