Is it okay to paint over varnish?
Reader Question: Can you paint acrylic over a varnished acrylic painting - should you find you need to fix something in the painting that has only come to light after varnishing?
It's okay to paint acrylic over a varnished acrylic painting in small moderation - for instance, if you need to do minor touch-ups here and there. After the new layer of acrylic dries, carefully varnish over the painting again. You can try to just varnish those small spots that you just painted, rather than varnishing the whole painting - however, you risk the varnish being noticeably uneven after it dries.
If you find that you have a large area that needs to be painted over, then it is best to remove the varnish. Check the label of your varnish bottle to see if it is removable and to find out how to remove it. The website of the brand you are using should also have instructions on how to remove varnish.
Hope that helps... All in all, as long as you are only touching up small areas with acrylic paint, then it is perfectly fine to paint over a varnish acrylic painting. I've done it a few times myself with no problems!