An oil-based varnish can be applied over completely dry acrylic paint with little difficulty. The polyurethane type of varnish is usually the best choice for this. However, oil-based varnishes typically have a natural amber tint and often become more yellow over time. Varnish will not adhere properly to oil-based paint without first adding a primer. If youre dealing with an older painted surface, the paint is often oil-based. To determine whether the paint is oil-based, test it by rubbing a small area with a cotton swab dipped in alcohol. Latex paint is easier to work with and dries more quickly, but it isnt quite as durable as oil-based paint. Latex is good for general painting projects such as walls and ceilings. Paint comes in a number of different finishes, from flat to high gloss. Yes, you absolutely can paint over varnish with latex -- provided you properly prepare the surface first. Applying latex paint over oil-based paint has less to do with the lower coat being oil-based than with the fact that this is a paint-over-paint project. Additionally, since oil-based paints tend to have a glossy sheen, it follows that the biggest issue to deal with will be glossiness, not the paints base content. polyurethane can be oil- or water-based, and you can use either kind over latex paint however, oil-based polyurethane tends to yellow as it ages, whereas water-based varieties stay. most enamel paints are alkyd resin-based, while some enamel paints have been made by adding varnish to oil-based paint. The origin of enamel paint was in the 1800s when the paints were less reliable and whitewash paints were known to smudge off. a quick video showing why preparation is so important when it comes to changing from an oil or varnished surface to a painted one. If you like this content, please subscribe to our channel for. bear in mind that exterior oil-based or marine spar varnishes have a tendency to yellow over time and will change the paint color. Virtually any type of varnish will work over latex paint except lacquer. Oil-based varnishes and polyurethanes can be used over latex paints. latex and oil base paints are rather toxic and hazardous to the environment. Many of us are surprised to learn this fact and most of us throw away left-over paint without realizing the harm they are doing to their environment.