Identifying Causes of Cracks in Paintings: Environmental or Contact-Caused
Editors Note: This is part of a series of posts by Elizabeth Burton on aspects of condition and conservation. This topics offer value to appraisers and collectors who want to understand deterioration and how it should be handled.
Discovering damage to a painting within your collection can be both upsetting and difficult to diagnose. Some damage is due to changes in climate, while much is human caused, such as handling during transport, reframing, rehanging, etc. Even still, some damage is inherent to the artist’s technique and can be stabilized and mitigated but cannot be reversed or protected against in the same way externally caused damage can. Paint layer cracking is one of the most visible and easily diagnosed types of damage to occur in paintings, with many possible causes and remedies. Cracking can result from impact to the front, back, or sides of the painting, from friction within the frame, from changes in climate which can cause stress on the primary support (wood, canvas, etc.), from heaviness of the paint, from interlayer cleavage due to the artist’s technique, from drying of the paint at the time of application, from vibration during transport, from keying out the painting, from poor adhesion, and much more. Here we will discuss a few common types of cracking and their causes.
Climate-Induced Cracking
If you notice cracking in the paint layer that results in pulling away of one layer or multiple layers of the paint, you may be looking at climate-induced or inherent vice-related cracking. The above photo demonstrates both: the painting was placed in a bathroom that experienced frequent dew-point humidity, while the paint was applied directly to a board without priming or much tooth. As such, when the board absorbed moisture, it repelled the paint, which also reacted, cracking and pulling away from the board; this eventually resulted in significant paint loss. You may notice wrinkling or curling of the paint or changes to the canvas or board when this type of cracking occurs.
Cracks may also occur throughout the paint layer along the weave of the canvas or the grain of the wood panel upon which the artist applied paint, typically appearing in a grid pattern. This is generally due to changes in the weave or moisture content of the panel due to fluctuations in relative humidity and is referred to as “tension cracking.”
Ageing, Drying, and Other Inherent-Vice Cracking
Drying cracks are another type of artist technique-related cracking; these generally pose little risk to the painting unless a significant change in the external climate occurs. Drying cracks appear as network cracks and are often shallow, affecting only certain colors or formulations of the paint. These cracks may also occur along brushstrokes. Cracks due to ageing of the paint are also considered artist-related or inherent vice because they result from the ageing processes specific to each formulation of paint within the paint layer.
Impact Cracking
Cracking due to impact is a very common type of cracking that can occur in acrylic, oil, and other paint layers due to contact with external objects, frequently someone’s fingertips as they handle the piece, an errant umbrella or backpack, the painting falling and hitting the ground, etc. Impact cracks will often be sigmoidal, meaning that there is a point of impact (often visible as a bump in the canvas, a loss in the center, or an oily fingerprint) surrounded by concentric, circular cracks. These echo the effect of a pebble dropping in a pool of water.
Keying-Out Induced Cracking
Cracking due to keying-out occurs when a painting on a canvas primary support (linen, cotton duck, etc.) and a wooden or metal secondary support with keys has been over-extended. Keying-out cracks will occur perpendicularly to the force applied and generally appear as a set of fine diagonal cracks at the corners of a painting. These may also occur in other instances of stress on the canvas, e.g. changes in relative humidity.
Stretcher/Strainer-Induced Cracking
Another type of cracking that may occur due to less than ideal circumstances is stretcher/strainer-induced cracking. This type of cracking may occur along the stretcher bars, cross pieces, bead, external edges of the stretcher bars, etc. and is often due to poor storage, framing, handling, or stretching. When the canvas lays too closely to the secondary support (stretcher or strainer), the weight of the canvas may cause the paint layer to crack along the stretcher bar or the bead (the additional raised portion at the far end of the stretcher bar that is intended to prevent contact between the rest of the bar and the canvas). This may also occur if another object is placed on top of the painting or if it is handled poorly. Cracks may also occur when a painting is removed from its stretcher and lined, unlined, or re-stretched.
Rolling-Induced Cracking
Cracking may occur throughout the paint layer when the painting has been removed from its secondary support and rolled for storage or transport. Rolling-induced cracking will appear as a set of horizontal cracks, from bottom to top or top to bottom, with the shortest distance between cracks at the point when the rolling began and the widest distance between cracks towards the end of the roll.
*A conservator should be contacted if the cracking has become more noticeable, is distracting or visually displeasing to the owner, or if peeling or instability of the paint has become apparent.