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GAC 400 on canvas back

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Hi, I have 84×30 inch canvas that is sized and primed, Gamblin PVA and Oil Primer. It is stretched on those 1×2 so called gallery stretchers. No matter how tight I try to stretch it I still get a wobbly bounce after each brush stroke. Is it safe to apply GAC 400 the back of the canvas to try and stiffen it up and reduce the movement, The stretcher can’t be keyed. Thanks.

Thanks for the answers. The stretcher can’t be keyed because it is one of those so called “Gallery” stretchers, mitred 1×2 frames the corners are fixed together as are the braces. I will try removing the canvas and glue masonite down on the stretcher then re-stretch the canvas. The canvas was pre stretched before I sized and primed it. Lewis, Steven

Hi Brian, I do have pliers and the canvas is cotton duck. I am not sure of the weight. I received the substrate attached to the stretcher and it was raw canvas. I sized and primed the raw canvas with the Gamblin products. I do find the canvas still loose even after priming. When I apply a stroke the canvas keeps bouncing and wobbles. I don’t have experience with large canvases I am not sure if it reasonable the expect that the wobble can be removed. Thanks. Lewis, Steven

Thank You Sarah.

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I would advise NOT applying GAC 400 to the reverse and here is why. It will be extremely hard to apply evenly and will therefore inevitably create subtle or even pronounced planar deformations to the canvas support upon drying. Such deformations would be nearly impossible to remove later on (this is another reason why we do not recommend the product “Tighten Up”). What is preventing the stretcher from being keyed out? You can always remove the canvas, fix/glue a piece of masonite or some type of rigid board to front side of the stretcher (you might consider sealing the panel first with a polyurethane or another type of varnish like Gamvar), and re-stretch the canvas. This will provide a more rigid support while you are painting.

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Kristin has covered the essential points but I have a couple of questions. Did you size and prime the canvas before stretching? It can be very difficult to stretch preprimed canvas (especially linen) when they already have an oil ground. Did you use canvas pliers or only the strength of your hand?

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Do you have canvas pliers? Is the canvas cotton or linen. The procedure would be the same but it is more difficult to stretch preprimed linen with an oil or alkyd ground. Sorry to sound dense, but make it perfectly clear did you size and prime the canvas while it was on the current strecher and it still is loose?

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​Hi – Coming to this a little late but as we make GAC 400 I thought it would be good to chime in. Kristin’s comments are spot on and is exactly why we never recommend applying GAC 400 to the back of a stretched canvas.  Over time it becomes almost inevitable that the difference in tension between the area of canvas you can get to and the perimeter strip that runs above the stretcher bar, which cannot be effectfively reached, will telegraph through to the front and appear as a ghosting on an inset rectangle. And even if that is slow to develop, or never becomes a factor, just setting up that distyinct difference in how planar stress is carried is not ideal.

Anyway, it sounds like you have things headed in the right direction. If you do ever want to give GAC 400 a try do so as a coating on the front of the raw canvas. 
Sarah Sands
Senior Technical Speecialist
Golden Artist Colors

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