Varnish starts to look old after a while. So, can you paint over varnished wood?
You can paint over varnished wood, but you must strip some parts of the finish. That’s because varnish has a glossy finish that repels paint and doesn’t allow them to penetrate. The sealant also has a higher solid-to-liquid ratio so it is very difficult for paints to adhere.
So, you must remove parts of it by stress sanding first. It’s recommended to use acrylic over a sealed surface, but oil-based paints also work.
Varnish Formula Explained
You shouldn’t paint directly over varnished wood. The sealant repels any type of paint and makes the adhesion difficult. So, before painting over it, you must remove some parts of the sealant (or the entire finish).
Varnish is common in old houses and furniture. So, this means it has a more traditional formula; it is designed with rigid resins, chemicals, and solvents that protect the material underneath and prevent liquid from penetrating.
Unlike modern sealants that are formulated to be painted over, the varnish is designed to be the final coat. So, its traditional formula makes it almost impossible for the coating to be applied over.
Varnish contains resins, compounds, and solvents, and has a higher ratio of solids to liquid (higher volume of solid compounds), all these chemicals make it super strong.
Why Doesn’t Paint Stick To It?
Paint doesn’t stick to varnished wood because the sealant when dry forms a glossy finish that repels liquid. Because of its moisture-resistant glossy finish, the paint can’t bite into the wood and won’t stick properly.
Varnish is filled with several resins and solvents. These compounds give it a super thick and moisture-resistant finish. Its finish prevents any liquid (oil or water) from penetrating the wood. Since paint can’t get to the wood, it won’t stick over it. Its finish is also glossy, so the coating will slide off.
The combination of these factors makes it almost impossible for the paint to stick to varnish. So, you must either sand or remove the sealant coating.
How To Paint Over Varnished Wood?
Painting over varnished wood isn’t hard, but you must have the right tools. Here are the tools that you need:
- Fine-Grit Sandpaper
- Water-based Acrylic Paint
- Latex Primer
- Drop Cloth
- A Sealant
1. Prep The Wood
First, check the wood condition. If the wood is rotten, you must repair it first. To repair rotten or damaged wood, use wood filler and fill the holes.
2. Stress Sand The Wood
You don’t need to remove the entire finish before painting over it. You just need to remove a part of the sealant and roughen it so the paint can penetrate and bite into it.
To remove varnish from wood, use a sander or a chemical-based paint remover. Removing it by sanding is safer, but takes a lot of time. On the other hand, a chemical-based paint stripper removes it faster, but it can discolor the wood.
For this guide, I’ll recommend sanding it.
To sand off the varnish, use fine-grit sandpaper (220-grit). The fine-grit sandpaper is not coarse enough to remove the entire finish, but it will remove its glossy layer. Sand the entire finish until you can see the wood grain.
You shouldn’t use coarse or medium-grit sandpaper as it will remove the finish and the top layer of wood. Unless that’s what you want.
3. Sand The Wood Again
After sanding off the finish, you must sand the wood grain. Sanding removes imperfections and bumps from the surface and allows the next layer to stick better. To sand wood, start with fine-grit sandpaper (220-grit) and finish with ultra fine-grit sandpaper (320-grit).
You must remove the dust that has been produced by sanding. To remove dust, wipe the surface with a clean rag or a vacuum.
4. Apply Two Coats of Primer
The primer creates a smooth surface (layer), so the next coating can stick better. It also hides imperfections and fills holes in the surface.
You must use a primer compatible with the paint you will apply. For oil-based paints, use an oil-based primer and for water-based paints, use a water-based primer.
Use a paintbrush to apply 2 thin coats of primer. The first coat should dry before you apply the second one. Once the second coat of primer dries, sand the prime coating with ultra-fine sandpaper.
5. Apply Two Coats of Paint
If you applied water-based primer, use acrylic paint. If you apply oil-based primer, use enamel paint. For water-based paints, apply three coats, and for oil-based paints, apply 2 coats.
You don’t need to sand between coats. Just wait until the first coat dries before applying the next one.
6. Seal With Top Coat
Optionally, you can seal the finish (again) with a sealant. The sealant will produce a glossy layer over the finish and protect it from moisture, scratches, and other damage. You can use polyurethane for this.
Related Read: Using Varnish Over Old Varnish?
Types of Paints To Use
It’s recommended to use water-based acrylic or latex paint over varnished wood. Water-based paints are user-friendly, dry fast, and have good adhesion qualities. You can also seal them with any type of sealant and get a high-gloss finish.
However, you can also use oil-based paint, but you must remove the entire finish first. Also, you must apply a stain-blocking primer over the surface.
If you remove the varnish from the wood, you can use any type of paint you want. However, you will wear off the wood every time you remove a finish from it. That’s why it’s recommended to paint over a finish rather than remove it.
Is Sanding Necessary?
You can paint over varnish without sanding, but the paint won’t adhere properly. That’s because sanding helps remove imperfections and creates a smooth surface for the next coating to stick. If you don’t sand, the coating won’t stick properly and the finish will be uneven and have bumps.
However, if you prime the surface, you don’t have to sand it. That’s because the primer will hide imperfections, fill holes, and create a smooth surface for the next coating to stick to. So, sanding isn’t necessary.
Painting over varnished wood is possible. But to get the best result, the sealant must be sanded and primed first or removed entirely.