Old acrylic painting on canvas

​In general painting new paintings on top of old ones is not a good idea, especially with oils, which get more translucent with age. Plus you end up with a complex sandwich of materials aging in different ways, which just adds a lot of unknown risks.  Oil paintings are complex enough in themselves that adding even more variables to the equation is just not great.

That said, if it was purely for a study or casual work, you could apply several coats of an acrylic gesso and proceed from there. At least I think that is less complicated than using an oil ground. But be forewarned, in my experience, you simply never know when a study might go astray and have the gall to become something you love and want to keep! Lastly, if it is about saving money, removing the canvas, flipping it over, restretching and applying a fresh size and appropriate ground would be better than directly painting on top of the older painting.

I am sure others might have other thoughts as well.

​I think most would agree that we artists are a thrifty lot, and we hate waste. I heartily agree with Sarah’s suggestion to prime the reverse rather than top-coating the painted side with additional primer. It is, however, worth considering how a potential collector or gallery owner will react to a recycled canvas. Some may find it charming, and others may leverage it to press for a discount. For a commission, especially a formal portrait, I would use only a brand new canvas.