Rethinking old methods of reducing paint cracks in modern paintings
Raised and tented cracks in paint and ground layers, quilted, slackened canvases, and deformations are just a few of many condition issues we can successfully treat at Fraser Spafford Ricci Art & Archival Conservation. These are common conditions we see across many traditional paintings on canvas. Well-developed treatment strategies have been refined over the decades to treat these conditions, and now, we are seeing the issues arise in younger, modern paintings. However, some modern oil paint media do not respond like a traditional oil paint, showing sensitivities that make us reevaluate our treatment approach, pushing us to modify tried and true techniques for each unique case.
During the modern era, artists were introduced to a whole range of new paints and synthetic mediums that opened up their world of artistic expression. Some of these modern materials have different aging properties than traditional oil paintings using centuries-old materials and techniques, rand are much more sensitive to treat. The increased use of cotton canvas since the early 19th century has also added another level of complexity to our treatment strategies due to its higher affinity to absorb water. Compared to traditional linen and hemp supports, cotton is much more reactive to humidity. With this newer generation of paintings showing more paint sensitivity and reactivity to environmental conditions, we are being faced with new complex issues, such as how to treat heavily cracked modern paintings.
Cracks are normal conditions of aging, whether they are accidental or caused through physical force, or inherent from the natural drying or curing process of the paint media. In some cases, they can form depending on the type of paint/ground layers that were used by the artist and whether they become brittle with age. The type and condition of the canvas support could also contribute to their formation. In most cases, the root cause is a combination of many factors, but crack growth tends to be exacerbated by poor storage conditions and environmental factors.
Tented cracks are those where the paint has raised edges surrounding the canvas which is pulled forward toward the paint surface to form a crease.
Sometimes, cracks on a painting are “tented” meaning that the paint has raised edges surrounding canvas which has pulled forward toward the paint surface. Merely lining a painting with tented cracks results in an overlap of the paint at the crack, and the canvas must be eased to remove the crease under the crack for the paint to be able to lay down. Typical treatment of raised, tented cracks in a conservation lab often include: 1) controlled tensioning on a working stretcher (also termed Dutch Stretcher) to maintain planarity and allow expansion of the canvas during treatment to draw out quilting if room is needed for tented paint to lay completely flat and avoid overlap, 2) vapour relaxation treatment to relax the paint and ground layers, in turn lowering the height of raised cracks, and, 3) lining to adhere the painting to a secondary supportive fabric with an adhesive, both strong enough to hold the weak canvas down which in turn holds the paint cracks in a lowered position to keep the painting flat over the long-term.
We should add that we do not treat cracks until a thorough cleaning is completed, because we do not wish to draw dirt and grime into a paint surface nor into cracks; for acrylic paint, we use high conductivity aqueous solutions in special preparations for safest cleaning. Not all cracks require treatment and we normally do not treat cracks unless they are unstable and affect the long-term integrity of the painting. But, in some cases, cracks are so prominent that they become a visual interference, and the artwork cannot be enjoyed with the distraction of visible cracks; in these cases some owners or custodians ask that the cracks be minimized visually to better show the artist’s intent and image.
We can use as examples three complex projects where FSR Conservation has successfully treated modern oil paintings exhibiting varying degrees of crack formation and instability. We were faced with unique challenges with each treatment that we were able to successfully overcome, providing valuable insight into how we can apply this knowledge to future conservation treatments of sensitive modern paintings.
Example 1: Takao Tanabe: “Reflections At Dawn”, 1958, oil on canvas
This painting is a great example of a modern oil painting executed on a thin and fairly reactive cotton canvas. Because the paint/ground layers are stronger than the canvas itself, the painting acquired numerous cracks that were raised, and pulled up the weak canvas along the crack lines. To minimize the height of the cracks and restore flatness to the canvas, this painting needed in-depth repeated tensioning while in a vapour relaxation chamber. The canvas was extremely reactive and had a lot of stretch that required the maintenance of strong continuous tension throughout the course of treatment to ensure flatness of the cracks, paint and ground layers.
Tensioning on working stretcher
Before treatment, raised cracks at bottom left shown in raking light
After treatment, bottom left shown in raking light, cracks are lowered.
After this extensive treatment, the cracks were significantly minimized and the canvas was rendered immobile with lining, but some crack lines were still visible and distracting. We developed a special method of infilling each crack line with a pigmented fill to further recede their appearance. In some cases, like in this treatment, most of the cracks had visually disappeared and the overall visual quality of the painting was restored. We had never seen this type of reactivity of the canvas support before, especially working with more traditional paintings, but this treatment shed light on the inherent sensitivities of cotton canvas, informing us of the best way to approach its treatment in the future.
After lining which immobilizes the canvas, cracks can be infilled with pigmented fills.
Before, detail of raised cracks are visually distracting.
After treatment, cracks are lowered and much less visible.
Example 2: Marion Nicoll: East from the Mountains, 1962, oil on canvas
Condition issues of raised stubborn cracks, a reactive cotton canvas, and sensitive paint media were all encountered in our treatment of this painting. The painting was held under constant tension while being carefully expanded on a working stretcher but the vapour relaxation treatment solution and lining treatments required modification to accommodate the paint media’s inherent sensitivity to the organic solvents and heat levels that are commonly used in the traditional approach.
Painting with canvas extensions attached to working stretcher.
Painting tension increased while humidifying on suction table to draw out raised cracks.
Applying consolidant to warmed painting on heated suction table.
Consolidant carefully applied into each crack.
Measuring temperature of painting during lining
After this extensive treatment, the cracks were significantly minimized and the canvas was rendered immobile with lining, but some crack lines were still visible and distracting. We developed a special method of infilling each crack line with a pigmented fill to further recede their appearance. In some cases, like in this treatment, most of the cracks had visually disappeared and the overall visual quality of the painting was restored. We had never seen this type of reactivity of the canvas support before, especially working with more traditional paintings, but this treatment shed light on the inherent sensitivities of cotton canvas, informing us of the best way to approach its treatment in the future with a network of distracting raised cracks.
Before, the painting has raised cracks in the paint layer. The thin canvas has risen to follow the cracks forward, creating tented cracks.
After treatment, the paint and canvas are more in plane following humidification and tension, consolidation and lining.
Before, the cracks at bottom right are very raised and apparent.
After treatment, the canvas quilting and cracks are lowered and stable.
Before treatment, detail of raised crack patterns at bottom right.
After treatment, the cracks at bottom right are lowered, stable, and less distracting.
Mentorship from seasoned conservation professionals was very important in this treatment, as we learned about the benefits of using pure water vapour versus the use of organic solvents, and the use of a membrane-less lining versus a fully enclosed lining and temperature control in this treatment, which was a first in our lab. We were surprised by the overall efficacy of these modifications, and it has since opened doors to more effective treatment possibilities for highly sensitive paintings.
Example 3: oil on canvas painting, 1960’s
In a more recent treatment, we were faced with a modern 1960s oil on cotton canvas painting showing similar sensitivities to the Marion Nicoll painting. We thus felt we knew exactly how to treat the raised cracks, however, we discovered original artist adjustments which interfered with our ability to support the weak canvas with an adhered lining. To properly line the painting, the artist’s modifications would have needed to be removed, and we try always to preserve the authenticity of the artwork. A conservator brainstorming session in the lab eventually led us, yet again, to modify our approach to preserve the painting’s originality. Following canvas tensioning on a working stretcher and slowly relaxing the painting in a controlled humidity chamber, each crack was consolidated, and underwent repeated localized humidification and flattening cycles while under tension. This method was slow and time-consuming but, in the end, we were pleasantly surprised with what we could achieve without the need of a supportive lining.
Before treatment (raking light), the canvas has deformations and the paint has raised cracks.
After treatment (raking light), the canvas and paint are in plane.
Before treatment (raking light), the raised cracks are very visually distracting.
After treatment (raking light), the canvas and the cracks are eased flat
Without a lining support, the visual authenticity of the painting was retained, but the thin cotton canvas is still inherently reactive and it was necessary to implement supporting preventive conservation measures to aid the canvas in planarity over time. The original fixed strainer was replaced with a new expandable stretcher which allows tension and tautness to be maintained across the canvas to encourage the cracks not to rise over time. Attaching a polycarbonate (Lexan) backing to the verso, and displaying and storing the painting in a minimally fluctuating environment will also help to reduce the future movement of the canvas and paint/ground layers, and the potential growth of cracks.
Emily Min, Senior Conservator of Paintings, May 22, 2024