Sizing Paper/Thinning Acrylic Paint

Discussion in 'Tips, Tutorials & Tools' started by Fishcarver, Aug 22, 2004.

  1. Fishcarver

    Fishcarver Active Member

    If you are going to prepare cardstock for lamination and/or painting, try using some acrylic matte medium (=matte acrylic varnish) thinned with a little distilled water to size the paper. Allow to penetrate/surface dry, then press until needed (I use a stack of smooth-surfaced ceramic tiles. This works also as a medium for thinning acrylic paint. Use 1 part varnish to 2 parts water: a little isopropyl alcohol can be stirred in to speed drying, as can a hair dryer.

  2. Square

    Square Member

    Fishcarver what does this actually achieve?
    I guess I don't understand the need for it...
    Thanx Square
  3. Leif Oh

    Leif Oh Member

    I think I get the idea (maybe). It would pre-shrink the paper, so that laminating (glueing) on to thicker cardboard will not warp the whole thing. Right? Good idea.

    That's what water-colour painters do before starting painting. They tape the paper to a board, and paint the whole sheet with water, then let it dry. No wrinkels or waves in the paper when you apply water colour after that. Same principle, right?

    But why the diluted matt acrylic varnish? And why the distilled water - is it really that sensitive?

    The idea appeals to me, sort of instinctively, but I can't figure out the reason. Can you print on this pre-prepared paper?

    Or is the idea to pre-prepare the thicker cardboard only, not the paper to be glued on? I guess I'll have to find out by trial-and-error.

    Anyway, thanks for the idea - would have never thought of that on my own!

  4. Fishcarver

    Fishcarver Active Member


    Basically, the point of sizing uncoated thicker stock, to/with which you will be laminating thinner pieces, is to prevent the glue being used for the lamination process being absorbed unevenly by the thicker stock, leading to wrinkles/lumps/adhesion problems. I suppose you could do the same thing with a lacquer or acrylic-based sanding sealer, or with "nitrocellulose dope" (whatever that is) as described in Alvar Hansen's book.

    Experience with my carving/painting classes has taught me that some acrylics are sensitive to the chlorine or minerals present in tap water, and may lump or curdle (a deadly problem when using an airbrush): I avoid the problem by using distilled water.

    Also, I've found that giving the printed sheets of the model a light spray of Testors' Dull Cote and allowing them to dry before beginning to cut them out strengthens the paper and protects the finish.

  5. Leif Oh

    Leif Oh Member

    OK. Got it. Wasn't like I thought, but good all the same. Thanks again!

    As for Testor's Dull Cote, I use a spray can of Windsor & Newton's "All purpose Varnish" (for General Purpose, Artis & Crafts; Matt). That's what they recommended at the artists' shop.

    Only objection I have (a big one at that) is that it smells something awfully strong; not suitable really for use indoors, in a small apartment.

  6. Fishcarver

    Fishcarver Active Member

    Sizing and Spraying


    I hear you! WHEW!!! (especially here, in winter!!)

    I'll hunt around for a set of plans for a little home-brew spray booth! :idea:
  7. wunwinglow

    wunwinglow Active Member

    Nitrocellulose dope is the stuff aeromodellers used to paint/spray onto the tissue paper covering on flying models. It has a very volatile solvent, pluse a 'varnish' material, which seals the tissue paper and makes it water, and fuel resistant. You had to get it on very evenly and quickly, as it shrank the tissue ferociously, pulling it tight. And often, pulling the structure out of shape as well! And yes, it stank to high heaven!! And yes, breath the fumes for a minute or two, and you felt like you were floating to heaven...

    I think aeromodellers use iron-on plastic materials now, or fly models made from expanded foam.
  8. Leif Oh

    Leif Oh Member

    Jim, many thanks for the good thought, and the offer of plans for a homebrew spray booth, but one thing I've decided against is to build another unwieldy contraption to clutter up the apartment. If necessary, I'll rather go out on the staircase and make the neighbours wonder what's cooking.

    Tim, I still get off on the smell of tissue dope, after growing up on it, and spending a great part of my life using it on balsa, tissue , and silk covered models.

    Trouble is, not everybody does, and I've finally come to the realization that I've caused enough aggravation around the house over all those years. Enough is enough, which is why I find a particular pleasure in everything water soluble these days.

  9. j77ason

    j77ason New Member

    Ugh, Yukh - I have been building card models for 25 years and i use PVA glue. It is white in colour and quite thick. You only need enough (wet) as you would find on the back of a postage stamp.
    You must paint the PVA glue onto both surfaces, the card which you are going to stick your paper to and the back side of the paper (all over). Then you carefully lay the glued surface of the paper onto the card, making sure you lay it without bubbles, or creases. It is really easy to do with practice.
    Use a soft cloth or towel to finally wipe over the paper to get a good join, but be carefull not to tear the paper.
    Leave the glued up jobs overnight to dry. You will find that the paper will shrink itself onto the card and all bubbles will disappear overnight.
    If your card model is warped (for some reason) lightly spray water onto the warped parts and leave to dry. Usually this solves any warping problems. These are often caused by the way parts are glued together in dry card. Wetting the card allows it to reshape how you want it naturally.
    Any sort of varnish used for sizing or whatever, before assembly causes problems because the varnish absorbs into the pores of the card and restricts the glue you use from making a proper joint. A bit like varnishing 2 bits of wood - then trying to make a glued joint on a varnished finish - not happening.
    With card and paper, it is best to work it in it's green state, only varnishing once the model has been completed and painted.
    If you have a thin card finish and it needs "shrinking or tightening" try assembling the model and painting it with acryllic paints - I don't thin mine, just slap it on.
    THEN paint a thin coating of PVA glue over the final finish of your model and allow to dry overnight.
    Of course, if your model is not very robust, then you will need to pin it down to a flat board or some sort of framework, so that the drying PVA glue, does not cause further warping as the glue dries.

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