Q. What do you suggest for tightening a loose stretched canvas thats just been painted in oil paint?
A. Let me assume that youve painted on stretcher bars and that you mean really loose instead of only mildly loose. Lets also say that your artwork was painted yesterday as opposed to last month. If this is all true, place the painting in a warm, dry room and wait about a month to see whether the canvas tightens up on its own. Tightening your work before a month has passed might cause some thicker areas of the paint to crack on the surface, and the wet paint beneath could ooze out. But if the painting has been drying for more than a month and its still loose, theres a different procedure you should follow thats easy to do.
If youre using real stretcher bars, youll notice the small slots at the corners of each bar. These holes are for keys that often come with the bars (but, depending on the bars, you might have to buy these keys separately). Stand the painting on one edge and insert two keys in each corner of the stretcher bars. Then place a thin piece of cardboard between the back of the fabric and the bars, and strike each key lightly one time with a small hammer, working your way around the canvas. If that tightens it, youre done. You can tell whether the painting is tight enough by looking at the face plane of the picture: If its flat and taut (it doesnt have to be drum tight), youre finished. If not, repeat the process again, one gentle hammer strike per key, all the way around.
If this doesnt work, youll need to put the painting facedown on a clean piece of protective paper and remove the staples or tacks from two adjacent sides. Restretch these two sides using gentle, even pressure on your stretching pliers. After tightening, use one staple about every 1 to 2 inches to secure the canvas.
One note of caution: Oil paintings get more rigid and brittle as they age, so performing this operation on an older painting can cause it to flake or crack badly. This is especially true for paintings that have been exposed to colder temperatures—as in an oil painting thats been in storage in an unheated studio—so be careful when performing any of these procedures.
Jennifer Ball is an assistant editor for The Artists Magazine and Artists Sketchbook.