Illustrated Glossary

The gradual accumulation of materials on the surface of an object over time. This can include dust, dirt, soot, corrosion products, or other environmental deposits that adhere to a work of art or historic material. Accretions may obscure the original surface, alter the appearance, or contribute to long-term degradation if not carefully managed.

Adhesive residue refers to the remaining traces of glue, tape adhesive, mounting pastes, or other bonding materials left on the surface of an artwork or object after the original adhesive element has been removed or deteriorated. These residues can cause discoloration, staining, embrittlement, surface distortion, and long-term chemical or mechanical damage. In conservation, identifying the type of adhesive and safely reducing or removing its residue is essential to prevent further deterioration and restore visual integrity.

A network of cracks that forms in a painting over time as part of its natural ageing process. These fissures typically run through all layers, including the ground, paint, and varnish. Ageing cracks result from the slow, cumulative movement of the support—whether canvas, panel, or another substrate—responding to continuous, subtle fluctuations in temperature and relative humidity. As the support expands and contracts over the years, the more brittle paint and ground layers are unable to accommodate these dimensional changes, eventually developing a characteristic crackle pattern that reflects the painting’s material history and environmental exposure.

The component of a paint that acts as the agglutinant, holding pigment particles together and adhering them to the support. The binder forms the continuous, cohesive film that constitutes the paint layer once it dries or cures. Its chemical nature varies according to the painting technique—for example, drying oils in oil painting, animal glue or egg in tempera, or acrylic polymer emulsions in modern paints—giving each medium its characteristic handling properties, appearance, and long-term behavior.

A whitish or hazy appearance that forms in a paint or varnish layer as a result of microscopic defects—such as voids, granules, or fine fissures—that develop over time. These micro-irregularities scatter incident light, causing the affected area to appear lighter or more opaque than the surrounding surfaces. Blanching is often associated with ageing, environmental fluctuations, or localized changes in the optical properties of the coating.

The unwanted diffusion or migration of a colorant—such as dye, ink, or pigment—into adjacent areas of a work of art. Bleeding typically occurs when excess moisture, water, or certain solvents mobilize the colorant, allowing it to travel beyond its original boundaries. This alteration can blur edges, change tonal values, and compromise the visual integrity or legibility of the object.

A raised protuberance on a surface, often bubble-shaped, resulting from the separation of an applied layer—such as paint, varnish, or adhesive—from its underlying substrate. Blisters commonly form due to factors like moisture, heat, chemical reactions, or mechanical stress, and they can compromise both the appearance and stability of the affected material.

A superficial cloudy or dull area that forms within a varnish layer. Blooming is most commonly caused by the deposition of atmospheric pollutants—such as ammonium sulfate—or by condensed moisture trapped in or on the varnish, often resulting from application under humid conditions. These factors alter the varnish’s optical properties, producing a whitish or hazy appearance on the surface.

Undulations, waves, or bulges that appear in a material—such as canvas or paper—that is intended to remain flat. Buckling typically results from uneven tension, fluctuations in humidity, or dimensional changes in the support or mounting materials.Buckling affects an area creating waves in a gradual, continuous way

Localized protrusions on a surface caused by pressure or deformation originating from within or beneath the material. Bulges may result from trapped moisture, structural distortions, detached layers, or the expansion of underlying components. Unlike buckling, which creates waves across a larger area, bulges form isolated bumps.

The powdering or friability of a paint surface caused by the deterioration or failure of the binding medium. As the binder breaks down—often due to weathering, ultraviolet exposure, or ageing—the pigment particles lose cohesion and are easily brushed or rubbed off, giving the surface a dusty or chalky appearance.

A small, thin fragment that breaks away from a surface as a result of external force, impact, or localized mechanical stress. Chips often expose the underlying material, creating sharp-edged losses that interrupt the original surface. They may occur in paint layers, plaster, ceramics, wood, and other brittle or rigid materials, and can be early indicators of structural weakness or damage from handling, accidental knocks, or environmental conditions.

A separation or loss of adhesion between layers in a stratigraphic structure—such as between paint layers, between paint and ground, or between the ground and the support. Cleavage occurs when materials fail, become incompatible, or respond differently to environmental changes. It can manifest as lifting, tenting, or flaking and, if left untreated, may lead to further paint loss or structural instability.

A broad, uneven wrinkling of a material, such as paper or canvas, without sharp creases or folds. Cockling typically occurs when moisture causes differential expansion or contraction across the surface, producing a textured, wavy appearance. Do not confuse cockling and buckling: cockling refers to fine, irregular wrinkles, whereas buckling describes broad, continuous waves.

The process of stabilizing degraded, weakened, or friable areas of a material by introducing or applying substances that bind and hold them together. Consolidation strengthens fragile surfaces—such as flaking paint, powdering pigments, or deteriorated paper—without altering the original appearance, ensuring both structural stability and long-term preservation.

The deterioration of metals or metal-containing materials caused by chemical or electrochemical reactions with their environment. In art conservation, corrosion typically results from exposure to moisture, pollutants, salts, or other reactive agents, leading to surface alteration, loss of material, or the formation of corrosion products that may affect the object’s stability or appearance.

The formation of fractures or fissures in a material caused by internal or external stresses. In art conservation, cracking may result from aging, environmental fluctuations, mechanical forces, or inherent material weaknesses, and can affect both the stability and appearance of an object.

A network of small cracks or fine fracture lines that forms in a paint layer, varnish, or glaze. In art conservation, crackle may result from aging, drying stresses, environmental fluctuations, or incompatibilities between layers, and can affect both the appearance and structural stability of the surface.

Microscopic fissures that develop in the surface of a hardened or dried material, typically as a result of aging, environmental fluctuations, or internal stresses. In a varnish layer, crazing can alter light refraction and produce a hazy or opaque appearance.do not confuse with Booming or Blanching, Crazing is a physical cracking (visible network of micro-cracks), Blooming is a optical effect from moisture or disruption, not cracks.

A line, ridge, or visible mark formed in a flexible material as a result of folding, bending, or wrinkling, whether accidental or intentional. In conservation, creases may weaken the material along the fold and can be associated with distortion, fiber breakage, or surface abrasion.

A condition in which aged or weakened paint begins to lift and curl along crack edges, creating small concave or cup-shaped deformations in the paint layer. Cupping often indicates loss of adhesion and can progress to flaking or paint loss if not stabilized.

A straight, deliberate or accidental separation in a support caused by a sharp slicing action. In conservation, cuts may compromise structural integrity and often require stabilization or mending to prevent further damage.

The process of reducing or neutralizing the acid content of an artwork or artistic object, typically through the application of alkaline agents. Deacidification not only neutralizes existing acids but also deposits an alkaline reserve (buffer) to counteract future acid formation and slow long-term deterioration.

Changes or alterations in the overall form, plane, or dimensions of an object caused by internal or external stresses or forces. In conservation, deformations may include warping, buckling, dents, distortions, or shifts in alignment, and can affect both structural stability and visual appearance.

Similar to cleavage. The separation of a paint layer into its constituent strata, often caused by aging, environmental fluctuations, or loss of adhesion between layers. Delamination can lead to flaking, loss of material, and instability of the painted surface.

A localized impression, hollow, or depression formed on the surface of an object as a result of applied pressure or impact. Dents typically deform the material without breaking it, creating a displacement of fibers or substrate layers rather than a full rupture. In art conservation, dents may appear in paper, canvas, wooden panels, metal objects, or frames, and can be caused by handling, storage pressure, accidental impacts, or contact with protruding objects. Depending on the material and severity, dents may be reversible through controlled humidification, reshaping, or other conservation treatments.

A small, localized depression or indentation on a surface, typically shallow and rounded in form. Dimples may occur in a variety of materials—such as paper, canvas, wood, metal, or coatings—and can result from pressure, impact, manufacturing irregularities, or inherent material characteristics. In art conservation, dimples are usually minor distortions but may disrupt surface gloss, texture, or the visual continuity of an artwork. Treatment options vary depending on the substrate and may include controlled humidification, gentle reshaping, or surface consolidation when associated with more complex structural issues.

An unwanted alteration or shift in the original color of an object or material, typically resulting from aging, light exposure, pollutants, chemical reactions, or previous treatments. Discoloration may appear as darkening, yellowing, fading, or localized staining, and often affects both the aesthetic appearance and the interpretation of an artwork. In some cases, discoloration is irreversible, although some forms—such as surface staining or certain oxidation products—can be reduced through carefully controlled conservation treatments. Understanding the cause and extent of discoloration is essential for determining appropriate intervention and long-term preventive measures.

The process of replacing or filling in missing material in a work of art or object to restore visual continuity and structural integrity. Loss compensation may involve inpainting, filling, or reconstructing areas that have been lost due to damage, deterioration, or wear, while ensuring compatibility with the original materials.