Has this ever happened to you? The paint beads up and won't stick to the canvas? (We're talking acrylics here.) When it happens, it's easier to see when you've got more water in your paint. So, what the heck is going wrong, and how do you fix it?
The problem isn't with your paints, it's with that sweet little canvas that you got at such a good deal.... Every ready-made canvas you buy comes pre-primed with gesso (pronounced JESS-oh). Gesso is different from plain white paint, in that it has gluey properties. It covers the surface you're going to paint on, and its gluey properties help the paint stick to the surface. (In years and centuries past, gesso was actually made with glue from rabbit skins.) Most often you'll find white pigment in it (though you can also find black and clear gesso for acrylics).
In order to cut costs and keep the price low on those value canvases, sometimes manufacturers will thin the gesso down to the point where it just doesn't stick all that much. So although the label may say double-primed or triple-primed, the gesso that was sprayed on the canvas was thinned so much that it just doesn't do what you thought it would.
So, the solution? Prime your canvas with a nice coat of gesso. Some people like to apply multiple coats, let each coat dry thoroughly, and then sand it before applying the next coat. Sanding is a nice way of taking out the brush marks left by the gesso when it's thick — if that is important to you.
Then, when it's dry, you can get back to painting. Have fun!
Karen Lynn Ingalls
I am a working artist in Napa and Sonoma Counties, in northern California. I paint colorist landscapes of rural California, teach art classes, workshops, and private lessons, and live in Calistoga, California.