Above you see a commercial grade prestretched canvas. Apart from the crude construction of the thing there is another problem with this unit. The canvas is held in place with a plastic welting forced down into a little channel on the back of the stretcher. This practice only began in the last few years. I am sure it confers some advantage to the manufacturer, but its a problem for you and me. Here's why, they have also put glue around the edges of those stretchers. If the painting doesn't work out, when you pull the canvas off the stretchers you expose that glue. I can find no way to remove it. I have tried water, turpentine and a carborundum grinding wheel, okay, I'm kidding about the grinder, but nothing seems to take that glue off. When you stretch a new canvas on those stretchers inevitably all sorts of debris is embedded in that glue and ends up between your new canvas and the stretchers. It makes an appalling mess. I won't let the damn things in my studio any more.
I know some of you readers out there have never stretched a canvas and only buy the prestretched canvasses. Often the quality of the canvas they use to make those is very low unless you are buying the most expensive sort, which are quite nice. Another problem with only buying readymades is you end up with a house full of old stored paintings that are not the equal of the wonderful things you are making now. There is no reason to let all those stretcher bars go to waste. If you put new canvas on them you save a whole lot over throwing them away and buying new ones, and stretching canvas is not very hard to do.
I will do a post on stretching canvas soon. I can tell some of you are squirming, look, I have met plenty of art school graduates who have never stretched a canvas in their lives, its OK. I don't know who you are. But you need to learn this. Its easier than rolling your own cigarettes. I may do a post on that down the road as well. One of the goals of this blog is to teach you to paint affordably and here's where that starts. If you want to turn any kind of a profit down the road you will have to know how to control costs. When you are rich and famous you can buy prestretched oil primed linen on old growth redwood stretchers with startled looking spotted owls still clinging to them. For now you need to learn to stretch your own .