The superficial loss or damage of media (and often ground) as a result of mechanical action due to friction (rubbing or scraping)
Visible stress develops over time as a result of adverse environmental conditions, mechanical stresses or other causes. The cracks are through all the layers of paint appearing as individual fissures or a network of straight or barely curved lines, known as craquelure
Localised, rounded protruberances or swellings from within or underneath a paint layer, caused by pressure.
Paint or varnish film which is dry but is mechanically weak or soft. Often it has a greasy appearance.
A change or alteration of the original form, shape and/or dimensions of a material caused by the application of force, without a breech of the continuity of its parts. Deformations can occur due to environmental factors (eg. Humidity), heat produced by fire, direct influence of sunlight or the use of construction/conservation materials
Drying Crack, Alligator crack
A type of cracking found generally only in the upper paint layer, exposing the paint layers and/or support underneath. These generally form during the process of drying and are stable over time. They are formed when the upper layer(s) of paint dry before the lower layers.
Exudates are the components of a paint (often medium related) that have seeped or oozed out of the main body of fluidized paint. They are often yellow or brown. Exudates fluoresce, and can be seen with blue LED light or UV Fluorescence. DTMS of ESIMS is possible for analysis of the polar components that separate from the paint mass.
Feather cracks are a fine pattern of cracks coming out from a central or larger crack. They can affect all the paint and ground layers. Feather cracks are the result of mechanical stress
A defect which is sometimes apparent in dry films of coloured paint containing mixtures of different pigments. During drying one or more of the pigments separates or floats apart from the others and concentrates in streaks or patches on the surface of the film. This produces a variegated effect.
The extreme separation of different coloured pigments in a paint resulting in a different colour over the whole surface of the paint film that is markedly different from the colour of the newly applied wet film.
Hairline cracks are long, thin cracks that can go through all the paint and ground layers, but often are found in the upper layers of paint. They are caused by mechanical damage, sometimes the result of rolling a canvas incorrectly
Missing part of the paint layer(s) which affects its integrity. It produces a discontinuity across a surface. Lacunae are produced by accidents or loss of adhesion.
Mechanical cracks are the result of outside influences. Crack rings or spirals can occur when an object is knocked against an artwork. Scratches or rubbed areas may result in feather pattern cracks. Fragile areas require professional care by a trained conservator.
Microcracks are a fine network of microscopic cracks that can appear as an opaque layer, (partially) obscuring the image. It is often found in the varnish layer, but can also be formed in the upper paint layer. See also: Crizzling/Crazing
A whitish or translucent appearance in a varnish film which should normally be transparent
Impasto paint that has internally regained it's viscosity and moves with gravity at a very slow pace, often with a dry crust. It leaves a trail of liquid or re-dried paint that originates from the 'wet' centre.
The breaking up of the surface of a sprayed finish into cells or with small craters due to the insufficient flow to level out the layer produced by the spray gun
Partial detachment of a superficial layer, a detached coating that has been applied to the surface
Pinholes or Craters
Small circular tiny craters in the (paint) film up to a few millimeters in diameter usually with a centre surrounded by a hollow halo-like space.
Primary craquelure can develop in the ground, paint, or varnish layers as the artwork dries, for example, when a faster drying layer is applied over a slower drying layer or within extremely thick or lean layers of paint. Artificial dryers and additives to paint can make it crack. In the 19th century, the use of bitumen often caused alligator crack patterns that deformed many paintings. Sometimes painters intentionally induce crack patterns for contrived signs of corrosion and synthetic patinas.
Rubberised paint describes the paint texture after exudates have been extracted from the paint; the surface gloss of the paint becomes more matte after medium has been leached
Secondary cracks develop as a response to aging and environmental stresses. Desiccated layers may crack, separate and detach. Fine cracking or crazing occurs when a varnish layer becomes very old. Problems may arise if heavy applications of paint or weighty mixed media are used on comparatively scant supports. Thick paint pulls away from a canvas support or the canvas shrinks, sags or distorts. A panel painting may develop cracks due to the shrinkage of the wood. Structural weakness or damage to an artwork may develop over time.
Spiral Crack/ Radial Crack
Spiral cracks are circular cracks (often multiple circles) around a central point. They are formed by mechanical impact and radiate out from a central point. Spiral cracks are often a larger cracking pattern, and is often found in combination with deformation of the canvas.
star cracks are cracks which radiate out from a central point. They are caused by an impact with a sharp or pointed object. Generally star cracks are a small cracking pattern.
Stress Crack/Mechanical Crack
Cracks caused by various types of pressure or impact in the ground and paint layers, eventually resulting in the cracking (and flaking) of paint film
Stretcher Bar Crack
A line of cracks or crease in the ground and paint layers caused by repeated contact with the inner edges of the stretcher bar. The cracking pattern can indicate the size and shape of an original stretcher if it has been replaced at a later date with a new(er) one.
Metal soap formation within a layer leading to bulging
Exudation of oil matter from a paint film, varnish or lacquer after the film has apparently dried
when the drying process is compromised (the upper layers dry faster than the lower layers) the upper layer of paint pulls apart, leaving the under layer(s) visible. Also known as Alligator cracks or Fissures
The spotty appearance of a paint film which is caused by drops of water on the surface and which remains after the water has evaporated. The effect may or may not be permanent