Stretching a Sagging Canvas

High-quality stretched canvas are known to be very archival.   A canvas can be much lighter for hanging on a wall than a solid piece of wood or metal.   

But one issue with canvases is the possibility, over time, of them being slack or sagging.   A high-quality well-made stretched canvas will be less likely to do so.   But it can happen due to extreme temperature or humidity changes, age and time, being stored improperly, among other things.

The best thing to do is avoid these threats to your stretched canvas to begin with.   

There are several things one can do if a stretched canvas starts to sag.   Many canvas frames come with corner wedges than can be pushed by hand or with a small mallet or hammer into the corners of the stretched canvas frame to remove any sag and keep the canvas tight.   

If a stretched canvas has a splined background, one would have to use a special canvas stretching solution on the back that would tighten the weave of the canvas.   It can only do so much tightening though.   

Splined Back

The other two options include removing the canvas entirely and restapling to the stretcher bars.   

And the last option, which many conservators of very old and fragile paintings do, is to remove the canvas from the stretcher bars and gently mount it to a solid panel.   Raymar Panels got this idea from conservators and sells their linens directly on lightweight panels now.   

Linen canvas mounted on archival panel by Raymar Panels

In conclusion, a sagging canvas can be fixed.   The method to restretch it will be depend on the type of stretcher bars, whether stapled or splined onto the stretcher bars, age and value of the painting, and even size of the canvas.   But there is more than hope for a sagging canvas.   There are solutions that can actually improve the painting over time.