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MITRA Forum Question Details

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  • GAC 400 on canvas backApproveRejectUn-ApproveSubscribeUn-Unsubscribe
    Question asked 2017-01-06 12:24:16 ... Most recent comment 2017-01-06 12:30:00
    Flexible Supports Acrylic
    Hi, I have 84x30 inch canvas that is sized and primed, Gamblin PVA and Oil Primer. It is stretched on those 1x2 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.

Answers and Comments

  • EditDeleteModerator AnswerI 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.
    Kristin deGhetaldi
    2017-01-06 12:36:19
  • EditDeleteModerator AnswerKristin 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?
    Baade, Brian
    2017-01-06 12:56:04
  • ApproveRejectUn-ApproveUser CommentThanks for the answers. The stretcher can't be keyed because it is one of those so called "Gallery" stretchers, mitred 1x2 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
    2017-01-06 16:25:58
  • EditDeleteModerator AnswerDo 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?
    Baade, Brian
    2017-01-06 17:07:22
  • ApproveRejectUn-ApproveUser CommentHi 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
    2017-01-06 21:36:33
  • EditDeleteModerator Answer

    ​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

    Sands, Sarah
    2017-01-09 09:42:42
  • ApproveRejectUn-ApproveUser CommentThank You Sarah.
    2017-01-09 14:35:40
  • ApproveRejectUn-ApproveUser CommentOccassionally I have a large canvas that sags a bit, and very annoyingling brushstrokes hit the crossbars, especially when dealing with pregessoed linens. Keys can be used but I have found that turning the canvas face down, and spraying a generous amount of water (distilled preferable, but that is not always feasible) over the whole canvas evenly (this is important) has worked well. The canvas gets taut immediately but will sag again once dry and pushed around while painting. I use a water bottle to spot spray the corners at times to help tighten those proble areas. I will try and stretch my next large canvas using the corner in technique described in the Golden's Section on canvas stretching. Hopefully this will eliminate any sagging issues in the future. But for those traditionalists who have already stretched from the centre out, and have saggy corners, and wobbly canvases, your big water bottle or spray hose may be your best friend for now. Joanne Gervais , visual artist, Canada
    2017-01-14 12:47:37

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