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GAC 400: Fabric and Paper Stiffener

31 thoughts on “GAC 400: Fabric and Paper Stiffener”

  1. Very interesting! I work on lots of collages and have made many papier mache’ figures & painted sculptures. I will give this a try. Thanks for the information.

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    • Tina, not sure the total properties of Paverpol but it appears to be a vinylacetate polymer. Not sure of the other constituents, but possibly including some type of plaster as well? Just a guess based on the uses and drying times. The GAC 400 is an acrylic polymer that was originally developed for the textile industry to create additional hardness to polyesters. It is not a great film former, but an excellent hardener, especially if heat set. The drying time is similar to other acrylics. Hope this helps. Best, Mark

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  2. In traditional recipe for chalk ground you need rabbit skin glue so I’m wondering if I can use gac400 instead, as it’s suggested as the replacement for rsg. Thanks! Anna

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    • Hi Anna,

      We have recommended using our GAC 400 in place of Rabbit Skin Glue, but we do not recommend using it blended with chalk or any other solids to create a chalk ground. When used to stiffen canvas or linen in place of RSG, our recommendation is to apply the GAC 400 directly to the raw fabric so it soaks in well. Allow to dry overnight, then apply a coat of our GAC 100 to block oil absorption. Finally, apply a coat of our acrylic Gesso or an oil ground to the dry GAC 100 film.

      We also have a newer recommendation for using two coats of our GAC 200 to stiffen canvas and block oil absorption. Then, apply either our Gesso or an Oil Ground. Alternatively, we have seen that 3 to 5 coats of our Gesso will both stiffen the canvas and block oil absorption. Here is a link to an article from our Just Paint Newsletter where we outline these methods:

      Preparing a Canvas for Oil Painting: https://justpaint.org/preparing-a-canvas-for-oil-painting/

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  3. Can GAC400 be used as a glue? I looking for a way to make canvas covered panels. I’m wondering if I. Can apply gac400 to a board then stretch unprimed canvas over that and then cover the front with gac 400 too.

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  4. Hi, in the photo, you’re showing a piece of painted canvas being dipped into GAC 400 but the text says it should be applied to bare, unprimed canvas. I read elsewhere that using gac 400 on a painted canvas will case the paint to flake off. I want to paint and make a relatively flat sculptural piece that is supported, but am a bit confused about whether I can paint first, mould after A’s is my preference, or if I need to paint after using the gac 400. Thank you for your guidance.

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    • Hi Rebecca,…..You are right in that there is a photo that shows a piece of canvas with some acrylic color on it, and I can see how that could be confusing, and happy we can address this now. The color on that piece of canvas is very thin washes or stains; Fluid Acrylic thinned with a lot of water, so the canvas is still very porous. And of course, the other side is raw canvas, so the GAC 400 can still soak in very nicely to the canvas. So while using raw, unpainted canvas or other natural fabrics is best, if the acrylic paint is very thinned out, that can work as well. Where it would not work well is if the acrylic paint was a discreet thicker paint film that would block the absorption of the GAC 400 into the canvas. Generally speaking, I would say it would be best to paint after you have soaked, shaped and allowed the GAC 400 to dry thoroughly, but since the GAC 400 remains water sensitive unless heat set, we would suggest heat setting before painting.

      Depending on the exact kind of “flat sculptural” piece you are making, it might be possible to simply rely on some thicker applications of acrylic paints and mediums or gels or pastes to create your piece and not use GAC 400 at all. I have seen some pretty rugged sculptural canvas pieces ( large painted canvas collage ) that just use Gel fortified paint under and on the canvas to maintain enough rigidity for the crumpled canvas. I hope this answers your questions!

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  5. Can I use GAC 400 on (primed, artist grade) polyester canvas? I want to stiffen it to make it easier to adhere to a panel. Without a stiffener it tends to be very difficult to adhere down smooothly as it’s quite light and tends to pop up in numerous places. Hoping you can help!

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    • Hi Jenny,

      GAC 400 will not work very well on synthetic fabrics like Polyester. And I am not so sure stiffening the canvas would really help adhere it to a panel. If you are having trouble smoothing the canvas down onto a panel, it might be due to the particular acrylic medium you are using. Using a too thin medium can sometimes cause this “popping up” since it tends to spread out too thinly and not grab on the the fabric enough. We recommend using our Soft Gels or even our Regular Gels for this. You actually want the fabric to be soft and flexible rather than stiffer, so you can press it down easily into the wet Gel medium. Using a roller of some kind is a good idea. And, for larger areas, a tool called a notched trowel can be very helpful to quickly spread out the Gel onto the panel surface. Here is a link showing one related method adhering watercolor paper to a panel: Adhering Watercolor Paper to Panel: https://www.goldenpaints.com/videos/applying-paper-to-boardadhering-watercolor-paper-to-panel-using-golden-soft-gel

      If you have further questions don’t hesitate to call or email us in Tech Support!

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    • Hello Shelly,

      Our GAC 400 only works on porous fabrics and paper, although best with natural fabrics like canvas. It might stiffen the acrylic skin a bit, but we do not think it would be enough to create rigid structures. It must soak in the the material. You might want to consider using pieces of plexiglas that you attach the skins to, and then glue the plexiglas together using acrylic sheeting adhesive. Or, working on some kind of rigid structure that could hold the skins.

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  6. Hi, can this be applied to a paper sculpture with an airbrush in thin layers? I don’t want the paper to get too wet and lose its form.

    Also:

    -Does it provide water resistance?

    -Is it archival?

    -is it shiny?

    Thanks!

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    • Hello MP,…As we mention in this article, GAC 400 should soak into the fibers of the fabric or paper so it is functioning throughout the material. It will not work well if used as thin layers on the surface, so the only way it could possibly work via spraying, would be if you sprayed very aggressively so a lot of product soaked in to the fabric. But, this is so much more easily accomplished as shown in the article. You have to soak the paper or fabric. It does not provide very good water resistance but with heat setting, as we mention toward the end of the article, can increase water resistance. It can be considered archival in that as an acrylic, it is resistant to changes due to UV light. It tends to dry with a sheen.

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  7. hi! i recently bought raw linen and i’m trying to stretch it to make it work as a canvas. it is my first time to make a canvas with raw fabric and when i stretch it, unlike other ready-made cotton canvas rolls, it is extremely hard to balance the tension at each edge of the wood. (the weaved pattern is not perfectly vertical/horizontal)
    i saw a youtube video of making a canvas out of raw linen and found out that people apply gac400 after stretching the canvas, but would it okay to apply it before stretching it?
    or would there be any tips in making a raw linen canvas?
    thanks
    yoorim kim

    Reply
    • Hello Yoorim Kim,
      thank you for your comment. Linen behaves very differently to cotton canvas. It shrinks more during sizing and therefore it is not necessary, nor recommended, to staple on a raw linen canvas very tightly. This could cause too much stress on the stretcher bars when the linen shrinks. You could try to use pins first to position the canvas on the stretcher as is demonstrated here: A Remarkable Way to Stretch Canvases (https://justpaint.org/a-remarkable-way-to-stretch-canvases-and-other-essentials-of-canvas-preparation/), and then staple the canvas in place. Alternatively, you could adhere the linen to a wooden panel or a wall and size and prime a piece larger than what you need, than cut it and restretch it with the desired size and tension.
      We recommend GAC 400 (applied directly onto the raw canvas) for artists who want a stiffer linen or cotton canvas than what one would get with another acrylic or PVA size, but not as stiff as Rabbit Skin Glue size. Once the GAC 400 is dried we recommend another two layers of either GAC 100 or Fluid Matte Medium, or three coats of Acrylic Gesso. There are even more priming options than what I listed here and you will find them in the article Preparing a Canvas for Oil Painting (https://justpaint.org/preparing-a-canvas-for-oil-painting/). Let us know if you have more questions.

      Reply
  8. Hi Scott,
    I have been using GAC 400 to make small paper sculptures, but now I want to make a larger one and I am not sure that the paper will be rigid enough with just GAC 400. Is there anything that I can spray on to the sculpture after using the GAC 400 to make it stronger and more rigid?
    thanks
    Catherine

    Reply
    • Hello Anette,

      We would not recommend using GAC 400 as a size for handmade paper. It is likely too hard a film. There are many different chemicals used for post sizing of paper ( as opposed to sizing added to the wet paper pulp), and these can be purchased through any number of companies who sell these products. There are two types of sizing for paper: Internal and Surface sizing. Surface sizing can also blend over into the category of painting grounds, or surface preparation for painting, and in this case some of our acrylic mediums can certainly be used. But if you are adding to the wet pulp, then we recommend finding specific paper size chemicals. The most common surface size materials for handmade paper are various kinds of starches or gelatin. Sometimes acrylics are used and much depends on the specific level of absorbency or resistance to absorbency of water that you are looking for. For starters, if you wanted to try surface sizing of a paper, we would suggest something like our Fluid Matte Medium or High Flow Medium.

      https://solenis.com/en/solutions/pulp-paper-solutions/sizing-agents/

      Reply
    • Hi Lynette,

      All water borne acrylics are alkaline by nature, so yes, they are acid free in the wet state and would be considered neutral in the dry state.

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  9. I started work on larger stretched canvas piece, this my first time trying a rather detailed pencil drawing on something stretched and canvas has become rather slack. Can I apply GAC 400 to the back of the canvas to tighten if the front has several layers of gesso on it?

    Thanks A

    Reply
    • Hi Andrew,

      We do not recommend applying any coating to the back of a stretched canvas as this can create uneven tensions and problems in the future for the piece. Your best bet is to first try moistening the canvas from the back with some sprayed water and brushing that in, and then allowing it to naturally shrink and tighten. This can work but if your canvas is just not stretched tight enough, then removing the canvas and re-stretching will really be your best option. Also, be careful bearing down while drawing on a stretched canvas as this can cause the canvas to loosen. Best to have some kind of board under the canvas if possible.

      Reply
  10. Hi! Will this protect my paper from UV damage? I am using thin, coloured paper..similar to gift bag wrapping paper. the kind you stick in the top of the gift bag to hide the gifts! If I cover it with GAC 400 will it prevent Color fading from UV?

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  11. Scott – just got a gallon of GAC 400 to use on stretched canvas. My technique is pretty wet, but there is no submersion. But I want the canvas to be as tight as I can get it short of putting it on wood. So, I would be a candidate for the heat treatment and I have a heat gun I will use. That said, you mention above that for oils, you recommend GAC 400 and then GAC 100. If one were to do that, would that eliminate the need for the heat treatment? I use GAC 100 to seal my wood panels and it seems really water resistant. I appreciate it.

    Reply
    • Hi Greg,

      If you are painting with acrylics then using the GAC 400 to stiffen the canvas may not be a good idea. And using the GAC 100 over it will not make the GAC 400 film less water sensitive, so that could be a problem. Keep in mind that the GAC 400 will stiffen fabric but it will not make a stretched canvas so rigid it will be like a panel. It creates a fairly brittle thin acrylic film that stiffens the canvas but it really can also be delicate. So I don’t think it will do what you want it to do. GAC 100 or any of our fine art grade acrylics, all dry to micro porous films that are water resistant but not water proof. That means they breathe and allow air and water vapor to pass through. They do not technically “seal” a surface. If you want your canvas to be tight, then the way forward for that is to stretch it tightly on the stretcher and make sure your stretcher is sturdy enough to handle very tight stretching without warping. If you wanted to experiment with heat setting GAC 400 on a smaller canvas then I would say give it a try, but again, I am not sure it will offer what I think you want. I would try GAC 200 instead. Our more current advice for oil painters is to use several coats of GAC 200 on the raw canvas to stiffen and block oil. Then, Gesso or another painting ground over that. You must need to allow the GAC 200 to cure at 70 degrees F or higher. It will be more forgiving than the GAC 400 and will stiffen the canvas. Also, multiple coats of Molding Paste can create a pretty stiff canvas. Here is a link with a method: Creating a Smooth Surface Using Molding Paste: https://www.youtube.com/watch?v=NP3br4sx7Uo

      Reply

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