Cabinet paint won't adhere properly to a smooth or shiny surface. You don't need to completely remove the prior finish, just rough up the surface enough to give the primer something to stick to.
Many people believe you can't paint over varnished wood. This however is false. In order to paint over it you will need to use either oil or water-based paints. However, it the process is time consuming and you will have to complete all the steps if you want it to look professional.
If you plan on removing the varnish and then painting the wood, sanding can be an effective way to get rid of the varnish while prepping the wood at the same time. It's also a natural and chemical-free way to remove varnish. It can however be labour-intensive: Start with 150-grit sandpaper and sand the entire surface.
Luckily, you don't need to remove all the finish from the surface. Just roughing up the surface with fine grit sandpaper is enough to get the paint to stick to polyurethane. With a little elbow grease, you'll be ready to paint in no time!
Surfaces with varnish, polyurethanes, or other sealants or finishes require sanding before any paint can be properly applied. If not, the newly-painted surface will bubble, peel, crack or generally not stick.
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!
Sanding The Wood Surface
Sanding is one of those things people either love or hate, but whatever the case, many experts will agree it's an extremely important step if you're painting over polyurethane and you want your paint to stick properly. For smooth surfaces, you'll want to go coarse with 60- or 80-grit sandpaper.
Well, much in the same way the acidic properties of vinegar dissolve the bond paint has with wood, it does the same with varnish, although it does have a slightly different reaction compared to the one it has with wood.
Methods for Removing Varnish
Although sanding is quick, it also generates a lot of fine-particle dust that is easy to breathe in, and it may remove more wood than you wanted it to. If sanding isn't an option, then you will need to strip the wood instead. Stripping can be accomplished with a heat gun or solvents.
We recommend using Zinsser Bulls Eye 1-2-3 for glossy surfaces like varnished wood.
Stained wood nearly always has a protective finish of some kind, and this needs to be removed before painting can occur. While there are chemical products that can achieve this, most people choose to use sandpaper to scuff up the surface. As long as the glossiness is removed, your new paint can stick to it.
Even freshly finished cabinet doors won't look good if the cabinets are too worn or damaged. If it's just the finish or the hardware that's worn, but the wood itself is still solid, you should get good results from painting kitchen cabinets.
For the absolute best results, sand the surface thoroughly until you remove the polyurethane entirely, apply 3 layers of oil-based primer, and then paint the surface the same way you'd paint anything else.
You can, but you'll need to use a good primer first. Polyurethane creates a slick, plastic-like finish that most paints won't adhere to. A bonding primer will stick to the polyurethane and create a surface that's just textured enough to paint over easily. Think of primer as a glue.
You can remove both oil- and water-based polyurethanes from wood surfaces using paint stripper, denatured alcohol and lacquer thinner, or baking soda and vinegar.
Applying a Coat of Deglosser
They do not realize that there may indeed be another option. Applying a coat of deglosser, also known as liquid sandpaper, can work in much the same way as sandpaper but without the need for all the sweat. It etches the varnish and provides a new texture for the paint to adhere to.
Apply First Coat
After you've given the primer a chance to fully dry it's time to apply your first coat of paint. Apply a thin coat and give it time to dry completely before applying the next one. Altogether you'll likely need two or three coats.
You can generally skip sanding and priming before applying chalk paint, even when working with varnished wood pieces, because the paint can adhere to most surfaces.
Chalk paint is the best way to paint practically anything without sanding. It offers a gorgeous matte finish and no need to prepare the surface.
And yes, you can use latex over varnish, although that might not be your best choice. But, chances are, unless the chest was handmade by someone, it doesn't even have a varnish finish anyway. Most furniture factories have been using lacquers for decades. You can also paint successfully over lacquer.