Over-painting an old oil is often a mystery to artists. Why would you do this? When do you do this? Should you do this? And ... HOW do you do this? Yes this is recycling an old panel, but it's important to be mindful of your artistic intent for the painting and how to manipulate what exists into a better visual statement. Live with your painting. Does it say what you want it to say? If not use these technical tips to revamp and restate your art. 3 examples are show with glazes, scumbling, and layers to over-paint.
Terms used:
Transparent - see through to previous layers with a tint no 'milky' look to paint (like stained glass, or rose in a wine-glass for a glaze)
Opaque - no previous paint layer is shown with fully opaque paint (think of milk in a glass)
My opinion these days is I don't want to have mediocre art around... studies, plein air attempts half-done painting. I'd rather ruin a 'good' painting trying to make it better, versus not trying and settling for just okay. Often the last part of creating a painting is very personal. How can you find this intuitive stage and when can you destroy old work? This can be very hard to do. Start with work you know needs revamping. Then work your way up to paintings you know are good, but maybe after 'sitting' a while you know they could be better. Be aware that the art might get ruined. Understand this is how you will grow as an artist.