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How can I prevent a stretched canvas from warping more with each coat?
August 7, 2014 8:52 AM   Subscribe

The canvas warps when painted and then unwarps when it dries, what can I do to prevent this?

I built a simple but huge (5x8) canvas stretcher. I've built a lot of smaller canvases in past years (up to like 4 feet square), so I was fairly confident that this giant canvas was all good when it came out nice and straight and tight. Once we started painting on it last night pretty quickly the whole canvas started to warp pretty badly, so badly that one corner was skewed by about a foot from the opposite corner. Fortunately once we stopped painting and it dried it unwarped back straight. My painting partner is at home working on it again now, and apparently it's starting to twist again. What can I do to prevent this? Will it just stop doing this if the paint gets thick enough?

Some key information about why this is probably happening:
1. There are no cross bars. I've heard anything bigger than 4 feet needs them but since I've always worked smaller I have never needed them or had any warping problems. At the start I attached some thin molding pieces to the back as token cross bars, but when the warping started they just buckled like paper so they've been removed. We don't have access to the tools to do proper cross bars, and it's already assembled, so I'd really like to avoid dealing with them. But maybe nailing some triangles to the corners would help?

2. The canvas was not gessoed. We wanted to do a really minimal painting with raw canvas showing through. I figured that because we were using only acrylics it would be ok to skip gessoing and let the raw canvas shine through and we'd get a cool paint bleed effect from the canvas sucking up the paint. In retrospect maybe a clear gesso should have been used.

I've come up with a tentative plan for how to deal with this, but I'd like some mefi feedback as to whether or not this will actually work. The plan is to put the canvas face down, weigh down all the corners, evenly paint a thick coat over the entire back and then let it dry weighted down. Will that work? That plus some triangles in the corners maybe?
posted by cirrostratus to Media & Arts (5 answers total) 1 user marked this as a favorite
 
If no cross bars, then make your corner triangles BIG. Also, stop painting, let it dry, then sponge over the back with some hot water and let that dry. And in the future, yes, real cross bars. (You might try putting some in now and hold them in with more big triangles.
posted by sexyrobot at 9:07 AM on August 7


CROSS BARS. The triangles will help, too. Consider doing both. You can sort of nail this kind of thing to a full support of masonite or plywood, but it might just warp and pull the nails out.

Consider working your painting, then removing it from the bar and restretching it to a new bar.

I didn't see a mention of what you're using, but if you're using anything lighter duty than 1x2's, it's too light for this size.
posted by blnkfrnk at 12:17 PM on August 7


The stretcher bars were made of a 2x4 sliced in half at an angle, so each bar is probably about a 1x2.
posted by cirrostratus at 1:07 PM on August 7


That's pretty light weight for a canvas that size. I would definitely add cross bracing - you can get metal brackets to attach at a hardware store.
posted by leslies at 3:31 PM on August 7


Adding triangles to the corners will only reinforce the corners and won't prevent the frame from twisting to the kitty corners. You'll need to add some smaller internal braces that aren't tacked into place.

Gesso is used to create an ultra smooth surface and to prevent linseed oil from leeching into the fabric causing it to rot. You don't have to prime the back. I wouldn't.

Even though you've started painting on it when you/ if you restretch the canvas on the reinforced frame douse the back liberally with really hot water and, if you can, let it sit in front of a warm flow of air to help shrink it more to the frame which helps give the canvas some of its structure.
posted by redindiaink at 5:39 AM on August 8


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