Since writing this post yesterday, the stats counter has gone nuts. Iguess it's a subject that interests a lot of people. Because of this, I'm adding an update: Windsor and Newton wrote to me this morning and said
Thank you for your enquiry. You are perfectly correct that acrylic will not rot fabric and I am sure that the confusion is that people are getting mixed up with oil colour—that will rot fabric. Most fabric paints are acrylic based and you can safely continue to use the product as you do without fear of rotting.
You might have read the comments yesterday about the use of acrylic paint on fabric. I thought I'd just share my thoughts on why I do what I do, and the way I do it. It's a personal view but is formed after reading about the paints and talking to manufacturers and it's for you to make your own decisions - of course!
Do I need to Gesso?
The old fashioned proper gesso used as a ground for oil painting was a mixture of rabbit skin glue, gypsum, marble dust, and titanium dioxide. It is far too brittle to be used with fabric supports (ie a quilt! It would simply flake off the first time the quilt was rolled or folded.) It was used as a primer for oil painting. Modern gesso isn't gesso. It's an acrylic polymer primer invented about 50 years ago and is simply acrylic paint with calcium. It is used to smooth the surface, and seal it. (it was apparently an early marketing ploy to call it gesso so that it would appeal to traditional oil painters, which can be a bit confusing)
Whether or not you prime canvas or cotton fabrics is entirely a matter of choice rather than a prerequisite to painting. It depends on what look you're trying to achieve. "Acrylic paint itself will effectively seal porous surfaces, so there is no need to prime it if the desired effect is one that incorporates the character of the material" (Rheni Gauchid: The New Acrylics, and Nancy Reyner: Acrylic Revolution)
(It can be used as a glue as is therefore ace in mixed media art on fabric, but beware, if you use other types of media such as markal sticks which are oil based, you need to know that these can cause rot. It's not the acrylic but the linseed oil or other media.) Always use oil based products on top of the acrylic paint and not the other way around.
Acrylic paint dries quickly and is permanent once dry. It is colourfast and relatively flexible and ideal for using on fabric. If you can't get fabric paint I have found acrylic paint to be a brilliant stand in. Many fabric paints are simply acrylic paint with an additional fabric medium to keep the fabric soft after painting. It needs to be fixed with heat because of this medium. Acrylic paint doesn't need to be fixed in any way.
What is acrylic paint?
All paint is pigment mixed with something to make it stick to whatever you're painting on. Pure pigment would "fall" off.
Acrylic paint is adhesive to all sorts of surfaces including fabrics. It seals making it impervious to liquid (but of course, on a quilt, liquids can still get into the back and this will cause rot through mildew - this has nothing to do with the acrylic paint, and everything to do with how a quilt is stored.)
How does it work?
Acrylics are made up of three elements, a polymer emulsion, colour, and various other elements depending on the type of paint you use. They can include a type of anti freeze, surfactant, biocide, fungicide, thickener, defoamer, and PH stabilizer. Harsh, dangerous??? Well strange as it sounds, no!
"Acrylics dry through a continuous chemical reaction. They continue to dry indefinitely whilst in contact with air. Acrylic polymers are fully formed in the wet emulsion and the pigment is suspended in this liquid. As the paint dries, all of the volatile solvents in the paint evaporate from the film and through the substrate by capillary action. "
"As the water exits the film, the acrylic polymers drift closer to each other and form bonds fixing the pigment particles. The other solvents evaporate at a slower rate but they do go completely (hours/days/weeks, depending on the thickness of the paint". (If you use if as I do, then it's very quick indeed) When these elements have gone, the polymers form a honeycombe grid welding themselves to the fabric. The resulting film is very flexible and tough and will not yellow over time and is UV resistant.
Buy the best you can. Always use artists quality as you have a higher degree of pigments to mixers. Some of the very cheap acrylics have a lot of binder to pigment, and I suspect a few unsavoury ingredients as well - but that's just me speculating!
Liquid acrylics, and acrylic inks are especially good on fabric, but I use artists quality buttery textured paint, simply because it's what I already have in the studio.
If you're unsure, then of course you need to do more research yourself, but try to find out by writing to manufacturers who can explain the chemistry better than I can.
I don't have the arrogance to think that my quilts will be handed down through history. In all honesty, their life is limited to the length of mine, so longevity is not a prime concern - but I do feel that acrylics will last longer, and actually help preserve the cloth longer, than other media or indeed any fabric exposed to ordinary light and air.