Always sand the polyurethane before painting. If you don't invest time in sanding, your paint over polyurethane project won't be a success. Although these how-to painting steps are for kitchen cabinets, they also can be applied to wood floors, doors, or furniture that have a polyurethane finish on them.
If everything was done correctly, your polyurethane surface should be ready for paint without any issues. Water-based paint works just fine if your surface is primed correctly, however it's recommended you use oil-based paint for a more superior, long lasting finish.
It is generally not recommended to paint over varnished wood without sanding or priming first. Sanding ensures the paint adheres properly, while priming helps with paint coverage and durability. Skipping these steps can result in peeling or chipping paint.
Since the paint won't bond over polyurethane, it would be better to remove the finish with paint remover or sand it down thoroughly, effectively etching the surface of the polyurethane until there's no sheen left. Then it would be best to use a primer first before final painting.
You can paint over varnished wood as long as you use the right materials and painting process. The best paint to use is a water-based acrylic one. If you're using an oil-based paint only use an oil-based primer, not an acrylic one. “Sweet, this means it can be done!
While varnished wood does have some resistance to water and light scratches, it can make the surface of the wood non-porous, which can make it difficult for paint to adhere. However, with a little preparation and the right technique, applying paint to your varnished surface couldn't be easier.
Keep in mind that if you don't prepare the polyurethane surface, all the paint you apply will end up peeling off your project, which is a huge waste of your time and effort.
We recommend using Zinsser Bulls Eye 1-2-3 for glossy surfaces like varnished wood. Zinsser Bulls Eye is a 'bond coat' primer that's great for hard-to-stick surfaces as it offers excellent adhesion without sanding.
Use 180-grit sandpaper and work the wood until the varnish is no longer glossy. For corners and other tight areas, use a sanding sponge or a bit of sandpaper. It is not necessary to remove all traces of the varnish, but it is critical to remove as much of the glossy finish as possible.
Choosing the Best Paint for Varnished Wood
Latex Paint: Water-based, easy to clean, and available in various finishes. Suitable for indoor projects. Oil-Based Paint: More durable and better for high-traffic areas. Takes longer to dry but provides a smoother finish.
Zinsser BIN
This is a shellac-based paint designed to stick to difficult surfaces like varnished wood.
Liquid sandpaper is also referred to as deglosser and wet sanding. The advantage of using liquid sandpaper instead of regular sandpaper is that it's easier to apply and safer to use. You just rub liquid sandpaper over the object you wish to paint, wait a set amount of time and wipe off.
Scrub the polyurethane surface with fine-grit sandpaper.
Use small, circular motions and work in sections to scrape the entire surface and scuff up the polyurethane coating. You don't need to remove all of the polyurethane, but it needs to be scuffed so your primer and paint will stick to it.
Other Common Methods for Removing Polyurethane
Many people use sanding strips, sanders, or metal scrapers to gradually remove the substance. You might also opt to use a planer, which trims the surface to expose the bare wood underneath. Chemical strippers are another popular option.
Note that most polyurethanes do not adhere well to polypropylene, polyethylene, silicone or surfaces coated with fluoropolymers like Teflon.
For the best results, use a water-based primer that adheres to varnished surfaces without the need for sanding.
In most cases only one coat is necessary to prime most surfaces. If excessive absorption occurs over very porous substrates a second coat may be necessary. Spot priming is recommended only under high-hiding topcoat paints. For best results prime entire surface before painting.
Zinsser BIN is shellac-based, whereas 123 is water-based. This makes Zinsser Bullseye 123 a lot quicker and easier to apply. It's also better suited for use on bare wood, or to prime plastic and composite before painting. BIN may be harder to apply, but it is by far the better stain block.
Understanding Deglossers: What is a Deglosser? Deglossers, often referred to as liquid sandpaper, are chemical solutions designed to remove the glossy finish from surfaces without the need for physical sanding.
If you have various stains, shellac Bonding primer is the ideal choice. It can be used to cover rough surfaces and old varnish as well as metal and ceramic.
When it comes to priming varnished wood surfaces, Zinsser's Bulls Eye 1-2-3 is a top contender. This versatile water-based primer-sealer is perfect for interior and exterior use and offers exceptional adhesion without the need for sanding.
Sealing your wood isn't necessary, per se, but it does protect your investment. It prevents wood from becoming discolored or stained by liquids and from absorbing water. It can also provide a protective barrier against wear and tear.
By far the best results we have had and this is now our go-to product is Tikkurila Otex. It has good opacity so blocks the colour of dark varnish very well, it is fast drying so can be painted over very quickly in just over an hour.