GAC attack 100, night of the killer substrates!

Do I need to seal acrylic canvas before painting on it?

Being self-taught, I began painting on vintage “finds” from thrift stores.  My favorite was old luggage.  I rarely used fine art gessoed canvas or artists boards. Painting on all these old, experimental surfaces presented serious archival issues for my artwork.

Why you need an isolation coat if you paint on alternative surfaces, use a lot of heavy gels and textures, or use transparent acrylic pigments.

When acrylic paint and mediums dry, the water molecules actually travel back and forth between your paint and your painting surface.  When they do, they tend to bring dirt, debris, and funky stuff up from the substrate into the paint film.  Think of them as tag-alongs that nobody wants.  The effect is even more obvious when using transparent acrylic paint pigments.

So What?

The results are something called SID.  Surface Induced Discoloration. And it sucks.  Really.  Especially if it messes up your painting and ruins your beautiful colors.

Personally, I have seen this affect my lighter pigments more than dark colors.  When painting on improperly prepared surfaces, my light orange and yellow glazes turned out gritty and speckled looking.  Some of the funk from my substrate travel up into the paint during the drying / curing process.  See How long does it take for acrylic paint to dry?

Easy Fix

To avoid SID, the fix is easy.  Seal your surface before painting it.  Golden makes a product specifically formulated to prevent SID.  It is called GAC 100.  It dries clear and  a little slick.  If  you want a white surface with tooth, apply acrylic gesso on top of the GAC 100.  See our Acrylics101 article,  What is Acrylic Gesso?

Watch out for Gels especially

SID is more common when using heavy gels and mediums with your paint.  SID is also more common with thick transparent acrylic paints.   If you are a transparent person, you might need to worry.  You opaque types don’t need to be as concerned.

If you like to experiment with invent as you go techniques, we recommend playing it safe and using some GAC 100 before you start painting.  A little prep work up front can save you a lot of heartache later on.  If you are a traditional acrylic painter, rarely using gels or modern transparent pigments, you will probably be OK simply using gesso to prime your canvas.

Does this mean I need to GAC those pre-gessoed stretched acrylic canvas that I love to  buy?

We are a society that like convenience and pre-made goods.  I personally don’t want to mess with adding sealer and gesso to my canvas when I can buy them already pre-made.

But if you want to make absolutely certain that your artwork will not suffer from SID, the answer is indeed yes -  You need to GAC  it first.

I read a lot of forums on the internet, as well most every acrylic book I can get my hands on, I rarely see this topic discussed.  My guess is that as more  and more of us begin to use pre-gessoed canvas that are mass-produced in foriegn countries who cut corners to make more profit, we may all become more interested in SID.  My fear is that acrylic paint will get a bad wrap for it when actually it is the canvas manufacturers that are to blame.

GAC100 Wrap-Up:

The Golden website advises that Gesso alone is NOT enough to prevent Surface Induced Discoloration.  They have chemists working for them, I don’t.   So I am taking their word for it and adding a coat of GAC100 to my premade canvas nowdays.  It is another step, and another expensive, but I think it is worth it for a little insurance that my artwork will retain it vibrant color and transparency over time.

Note for Liqitex fans: The Liqutex offers their Gloss Medium and Varnish product as a sealer.  Their website advices to wash and dry your canvas prior to prepping with gesso to avoid SID.

I couldn’t find much mention of this SID phenomena on other fine art acrylic paint manufacturers website.  If you have additional information regarding this topic, by ALL means please contribute  by adding your comments below.

Written by Cindy Davis, editor of Acrylic Paint Review and an working acrylic painter.  Find her work at CindyDavisArt.com.