If you’re going to paint with oils, the simplest approach is just to go to an art or craft store, buy some stretched primed canvases, and paint on those. So far as I can tell, that’s what most people do, because it doesn’t involve any work or thought, and you can get a canvas pretty cheaply.
That’s not what I normally do. I don’t like painting on acrylic primer. (Which is usually, and misleadingly, labeled “gesso.” As I’ve said before, real gesso is made with hide glue and chalk or gypsum, not plastic.) Acrylic primer is rough on brushes because it has abrasives in it to provide tooth. Without those abrasives, it would be much too smooth, and the paint wouldn’t stick to it. It is also too “chattery” for my taste. By that I mean that the paint doesn’t flow as smoothly as I would like it to. Most acrylic-primed canvas is primed too thinly; it would be better if they applied another layer or two of primer. Some artists add more acrylic primer themselves, and that’s an improvement. But it’s still just acrylic primer. It is not fully clear whether oil paint on acrylic primer has good long-term archival properties. It is better than oil painting over acrylic paint, because the abrasives in the primer allow better mechanical adhesion between paint layers, but it has not yet proved itself over the long term.
A much better option, in my opinion, is an oil primer. That’s been the usual priming material for oil painting since about 1500 or so, and it’s still the best. Oil paint goes onto oil priming much more smoothly than it goes onto an acrylic priming. Unfortunately, it takes work and time to get an optimal oil priming.
You can buy oil primed canvas from a number of manufacturers and stretch your own. I’m sure you can get stretched oil-primed canvas, although it’s a bit hard to find. You can also stretch raw canvas, size with hide glue, and apply an oil priming on top of that. Personally, I prefer to paint on panels, so I make my own.
Although you could just use white oil paint, I’d suggest you check out products that are specifically intended as oil primings. Williamsburg makes both titanium and lead white oil primer. Studio Products makes a lead primer ground in black oil. Either way, you’ll pay about $50 US for a pint (0.47 liters) of primer. That much primer goes a very long way. My preference is to use a lead white oil primer, because it is the traditional material, because it has shown its ability to last for centuries, and because it is flexible and therefore highly resistant to cracking. If you don’t like to use lead-based paints, then titanium is certainly adequate.
I personally avoid alkyd-based primers. They dry quickly, but I just don’t trust alkyds as a base coat for oil paint. If you use alkyd paint, then an aklyd primer is probably optimal.
I usually paint on hardboard panels. I cut them to size with a table saw, then even and round the edges with a rasp. I clean the panel with denatured alcohol to remove any grease. Usually, I coat all sides of the panel with a couple of layers of hide glue to protect it, although that’s probably not necessary. Oil primer tends to be pretty thick, so I thin it slightly with spirits of turpentine. I apply it with a spatula, smoothing it down as much as possible. It helps to work in a clean room so that dirt and dust is unlikely to get into the primer. I then smooth it out even more using a soft fan brush dipped in turps. I let it dry for a few days, then apply another layer of primer. Since I am using lead paint, which is toxic, I am very careful to wear painting clothes and wash very thoroughly afterwards.
While you can paint on it within a couple of weeks, oil primer is best when it has cured for about six months. “What the %*@$#?!?,” you might say. “I don’t want to wait six months to paint!” My reply is this: are you going to be painting in six months? Then you can prep a bunch of panels or canvases right now. That won’t stop you from continuing to paint on whatever you have been painting on. If you like, you can see what it’s like to paint on lead priming that’s only a month or two old—it’s still better than acrylic priming. Oil priming that’s less than fully cured is a pleasant surface to paint on, but the paint goes on a little streaky. It’s hard to get a smooth coating on the first pass. I have occasionally used this characteristic to create specific textural effects, but overall it’s better to paint on cured primer.
I usually apply a thin imprimatura to tone the panel. Sometimes I paint into that wet; sometimes I let it dry first. Usually, I use a mixture of burnt umber, Mars black, and lead white, thinned down somewhat (not too much) with turps.
It takes awhile to get used to painting on lead primer. The surface is not absorbent, and it requires a lighter touch than acrylic primer. But, after some practice, I find it a much more pleasant surface to paint on.
31 March 2007: Many oil primers come in cans. After you open the can and put the lid back on, the primer is exposed to oxygen. It will then develop a film of dried paint on top. If you like, you can peel the film off and put it back after you’re done to prevent further drying. My preference is to cut a piece of plastic from a trash bag and press it down against the surface of the primer. This seals out oxygen and prevents drying.