A reasonable question
Here's a reasonable question from Jennifer... "Have you ever had any problems with the oil on top of the latex? Do you think house latex is better than say a regular acrylic artists paint?"
Jeni, Thanks for the question. When I was discussing the idea of this way of painting as part of my presentation at the Plein Air convention with Eric Rhodes, he said I should talk to some conservators about it. I talked with two. One said absolutely not, one should never paint with anything but oil on oil primed linen, preferably mounted or glued to a solid ground and never never never use cotton canvas (he seemed a little uptight), the other said no problem painting oil on gessoed canvas but wasn't sure about the oil over latex house paint. If the first guy was right, there will be hoards of disappointed collectors in years to come. For starts, most of the canvases sold in art stores are thinly gessoed cheap cotton canvases made in China. Plus I know a ton of artists who are painting oil over Kilz or house paint primer on wood or masonite. We will see what happens there.
The big issue seems to be that oil dries hard and brittle and latex acrylics expand and contract, but then so does a lot of canvases... including stretched linens, which is why I don't use them. The second issue is that acrylics don't have a surface structure that is ideal for oil to stick to. I looked up what is in commercial gesso, "Modern 'acrylic gesso' is a widely used ground that is a combination of calcium carbonate with an acrylic polymer medium latex". Sounds like acrylic latex to me. The only difference is the chalk thats added in for tooth. Something you can do if you want to spend the time (it's called chalk paint and is sold for crap loads of money at boutique stores).
So, for sure you don't want to paint oil over tube acrylic paint found in the art stores unless it's thinly painted. Though I do know a number of artists who work this way, as well as using water missable oil paints over acrylics. The way I do it is, I do the underpainting with with the house paints on gessoed canvas and then coat that with galkyd light and a tint of oil color, this gives me a binding surface for the oil paint. Then the next layers are thin glazes oil over the latex ground. The thicker I get the the more galkyd I add and the final top notes are mixed with a thickening alkyd medium, like Oleopasto or solvent free gel. My thinking is that with enough alkyd resin based mediums in the mix there should be enough flexibility inherent in the paint to last a long time.
Other ways around this issue are:
1) Just use house paints, you can have any color under the sun mixed by the quart for the price of a small tube of good oil. I'm thinking about going in to Home Depot and having about 25 or 30 colors mixed that I like and then using heavy gesso as a white and maybe a set of acrylic primary colors as tinters to bend the colors as desired.
2) Use house paints under and tube acrylics on top. There are enough kinds of acrylics (like Golden Open acrylics) and mediums to make it work the same as oil.
3) Coat the house latex underpainting with clear gesso to give the oil something to hold on to.
4) Work on a hard ground like masonite or gessoed wood panel.
5) Add plaster in to the house paint, there are ratios on line if you are curious. Just google how to make chalk paint.
6) Don't worry about it. If my paintings start falling apart in 20 years, I won't be around anyway. And apparently, when you buy a painting at any gallery it's an "as is" policy.
7) Let the conservators at the Metropolitan Museum of art deal with it... Latrec painted on cardboard for JimminyCrickets sake.
I will be consulting some paint chemists in the near future to flesh this out more. I want to make sure my paintings last a while. I'll let you know what I find out.