A Cure for a Warped Oil Painting
The wooden stretcher on which the canvas is stretched upon is warped itself. This might be due to damp or extreme temperature variations causing stresses in the wood. If the painting is large (over 2.5ftx2.5 feet) lack of support via crossbeams at the back of the painting may cause the canvas to ‘droop’ in the centre which could exacerbate over time.
The canvas has been improperly stretched in the first place. Pressure points may vary in the canvas, causing the weave to slacken one area and overstretched in another. This might manifest itself as distortions in the canvas weave which over time begin to give. This pressure difference may show up as small cracks along a ‘fault line’ of the oil painting.
Improper Use of Oil Mediums
Canvas warp can also be caused by improper use of art mediums. Linseed oil for instance retards oil paints’ drying time, whereas alkyd-based mediums will accelerate it. If both mediums were used in the same oil painting, the varying drying rates within the painting could cause pressure points in various areas of the painting which will be transmitted to the canvas, causing it to warp.
A Cure for a Warped Oil Painting
So once the problem occurs, what can the artist do? While there is no solution to cure all, the following actions might help:
Before doing anything, remove the varnish, (if the painting has been varnished). This is recommended as the varnish will over time ‘remember’ the distortion in the canvas. Varnish dries to a hard, clear film that is designed to protect the oil painting from damp and dust. Some of the old traditional varnishes tend to brittle in time and possibly crack at the warped area.
How to Remove Varnish from an Oil Painting
Special varnish removers can be purchased from artshops which is designed for oil painting (never use household products or turps). Follow the instructions. If the painting is old, take extra care. Place the painting on a level worktop. Place a little of the cleaner on a shallow dish to keep the rest clean. Dip a little onto a cotton bud to start with. Watch out if any of the oil paint comes up with the varnish as this is indicative the painting has been varnished before the painting has dried properly.
With a clean cotton swab, work over the oil painting in small sections, changing the swab frequently. Work in a dry, dust-free place.
Once the varnish has been removed, carefully remove the oil painting from the stretcher (if has been stretched). It is recommended to re-stretch a warped oil painting. Once liberated, place the painting face-up on a level worktop. Leave it for a day or so at room temperature. This will make the oil painting a little more flexible for re-stretching later.
Oiling Out an Oil Painting
You may 'oil out' parched areas of the oil painting. Oiling out an oil painting is covered in a separate article but works to renourish the oil paint and aid flexibility. Basically, oiling out entails the application of a little linseed oil to the painting as one would apply oil to parched wood to restore its oil content. Allow the oil to settle in the oil paint prior to restretching.
Now turn the oil painting on its front upon clean soft fabric to protect the surface. Place a new stretcher on top and carefully stretch the canvas. If the painting is particularly old, take care not to stretch it unduly. Follow the instructions on my other article on how to stretch canvas, by using the ‘rotation method’. Be sure that equal pressure has been exerted over the entire canvas during the stretching process but don’t pull too hard; only enough to ‘iron out’ the warp.
If the painting is large, crossbeams will be required at the back of the stretcher prior to stretching to provide extra support. You may revarnish the painting once it has been restretched.
Stretching Warped Canvas
Some warps are more stubborn than others, particularly if the painting has been warped over a long period. Efforts may not eradicate all warps, but could reduce them. The most stubborn types are when the canvas has been improperly stretched in the first place causing some of the weave to stretch more than others. Improper use of art mediums as outlined earlier can also be a stubborn problem.
More Articles about Oil Painting
How to stretch canvas for an oil painting
Guide to types of canvases for oil painting
How to glue canvas onto panel
Why is my painting cracking?
oiling out an oil painting
Types of gessoes for oil painting
A demonstration on working dark to light