This article is about a discussion I came across on POL where suggestions were made on how to avoid over-diluting acrylics.
Artist Robert Jones had an interesting story to tell about a painting accident he had had. The acrylic paint he had used appeared to have been under-bound in places, and lifted off and smeared as he was trying to varnish it. Fortunately Robert has been able to repair it and he doesn´t think the problem lay with the paint itself. He thinks he over diluted it, which caused the thinner paint to lift, and that it hadn’t dried throughout, which caused the thicker to smear.
Robert posted his experience on the POL website to ask if anybody had had a similar experience. There were numerous replies and I will try to give you the gist of it.
Personally I also dilute my acrylics when I want to achieve certain effects. I then tend to leave the painting to dry for a couple of weeks before I apply the varnish. Maybe that is why I have not had the problem Robert described.
I also know some experienced professional artists who use acrylics as an under painting for their oil paintings. Sometimes the acrylics are also watered down and left for about half an hour before starting on the oils. So the professionals could not have been too worried about it lifting off.
In the POL discussion someone put forward that he had seen a video on youtube which advocates using acrylic medium as a small addition to the painting water to help adhesion of the paint to the surface of the board or canvas or paper. It was said that acrylic paints are bound by an acrylic polymer which helps to extend the paint and holds it together. If excessively diluted the polymer binder is so diluted it ceases to hold the pigments together and the paint adhesion is compromised.
John Hammond was quoted warning against over-dilution of acrylics with water in his book “Capturing Light in Acrylics”. He was said to be citing the risk of lack of adhesion resulting from insufficient binder. He uses Liquitex, and his technique involves the use of multiple thin glazes, for which he thins the paint with their gloss glazing medium to produce a transparent glaze.
Robert came back to say that he hadn´t used any medium with acrylic for some 40 years, and has never had the sort of problem before. In future he wants to use a flow enhancer rather than water, and a glaze medium when appropriate, to thin the paint. He might also employ an isolating coat of medium, such as that made by Golden Acrylics, before applying varnish; while also delaying the point at which he applies varnish. Robert believes that early varnishing may have been three quarters of the problem. Incidentally, he also doubts that dilute paint would be a problem on watercolour paper suspecting that the dangers seem to arise with acrylics on canvas.
Professional use of Acrylics
Some professional acting as a technical adviser to a paint manufacturer told Robert that there is a known problem regarding ready-primed surfaces with over-diluted acrylics. It appears that some surfaces are sometimes? often? too shiny to accept the paint – lacking both tooth and absorbency.
His way of dealing with this was to wash the surface of canvas and canvas board with warm water and a very small amount of washing-up liquid – then to hold the panel against a raking light to see which areas continue to repel water. He would attack those, though carefully, with a nail brush, and dry thoroughly. He further recommended a coat of matt medium over the gesso to ensure maximum adhesion.
It was also mentioned that not all acrylic manufacturers actually sell a medium for use with the paint at all, and recommend water. Most of them offer things like glaze medium, gel thickeners, retarders, but not all make a medium for the generality of the painting, because you don’t really need one.
Someone wrote in later to say that he had learned something from the discussion. After never having added flow improver to the water before he bought some Daler-Rowney Flow Enhancer, added a quantity to water, and used just that pot of water for the areas where he wanted the paint to flow. He was happy to see how well it worked.
The discussion further elaborates on the issue of priming a canvas for painting in oils where the base layer or “Imprimatura” is often applied in acrylics to shine through several glazes of thinly applied layers of oil paint.
If you want to follow the whole discussion please click here.