How do you prepare a canvas for oil painting that already has paint on it, it is a used canvas?

I like to buy canvases at thrift stores because they are cheaper, but how do you prepare it to paint a new oil painting, i cant remember... please help. How do you prepare a canvas for oil painting that already has paint on it, it is a used canvas?
I've been a professional artist all my life http://www.giusepperussottoart.com


What I do is buy paint remover in a hardware store. It comes in a paste in a can. Simply spread the paste over the entire surface of the canvas with a palette knife. Let it stand for a few minutes. The paint will get soft, and you'll be able to scrape it off.


DO NOT use gesso on a canvas, as it is not flexible enough to accommodate the expansion and contraction of the canvas fibers when the weather changes, and, therefore will crack.


If you want to put an additional coating, get some flake white or titanium white paint. Spread it over the canvas evenly with a palette knife. Allow a week or two to dry. This will give you a strong and flexible surface that will outlive both of us.How do you prepare a canvas for oil painting that already has paint on it, it is a used canvas?
I like the idea of sanding...but no more than that... I like used canvases only because you can use them for practice...i like to paint my subject directly over the old, the challenge is more interesting...the faster you go the easier...using flat water based paints,go over your under-painting,then switch to oils...have fun...
I would simply gesso it and hope that the texture of the underpainting would not disturb the painting that went on the top. You are following a time-honored tradition--good luck.
gessoing over the top is an option, or, unstretch the canvas, and turn it around so you are painting on the backside of it
I agree,, I also sand down any high spots and then gesso after that,,, I have paintings that are forty years old and show no signs of anything coming thur