Varnish over Old Varnish: Can You Do it And How To?

After a while, varnish gets old, and you need to re-coat it. So, can you apply varnish over old varnish?

You can apply varnish over old varnish, but you must sand and prime the old varnish first. Varnish, when dry, forms a thick and glossy layer that repeals any type of liquid, including varnish and paints. 

If you don’t sand the varnish, the new coat won’t stick properly and will slide off the glossy finish. Sanding will create tiny holes where the new coat can stick. 

So, re-varnishing wood is possible. You just need the right steps, and that’s what we will explain. 

Varnish over Old Varnish Without Sanding

You can apply varnish over varnish without sanding, but you must prime the old varnish. Priming creates a smooth surface and allows the new coat of varnish to stick better. 

Whether you should sand the old varnish depends on how much of the old layer is remaining. If there isn’t much varnish left on the surface, you don’t have to sand it. However, if the old varnish still has a thick and glossy layer, you must lightly sand it.

Unlike traditional finishes, varnish doesn’t need to penetrate the surface to stick. Instead, the varnish is a topical finish that sticks over the top layer of paints. However, making varnish stick over a glossy finish is tricky. The varnish won’t be able to stay still over a glossy finish and will slide off. That’s why sanding is important.

Sanding removes the glossy layer of the previous varnish, removes imperfections, and helps the new varnish stick better. Once the glossy finish is off, the varnish can stay over the surface and will stick. 

However, priming can be an alternative to sanding. The primer will cover the glossy layer of varnish and allow the new varnish to stick without sliding off. 

Related Read: How To Apply Varnish With a Roller?

How To Apply Varnish Over Old Varnish?

You can apply varnish over varnish, but you need the right steps. Here they are:

1. Clean And Sand The Surface

The first thing you want to do when applying varnish over old varnish is to clean and sand the area.

First, you must clean the surface. Use a clean rag and wipe off the dust from the old varnish. Dust prevents the new coat from sticking but can also block some parts of sandpaper.

Once the surface is clean, sand it. To sand varnish, use 220-grit sandpaper. You can use rougher sandpaper if the glossy varnish isn’t coming off. You can use a power sander instead of sandpaper if it’s a large surface.

Sanding will produce a lot of dust, so once you are done, you must remove the dust off the surface. To remove dust, use a damp rag with water and use the dampened rag to wipe the surface. 

Related Read: Should You Paint Over Chalk Paint?

2. Add A Coat Of Primer

To help the varnish stick better, you have to add a coat of primer.

If the paint underneath the old varnish is oil-based, the new varnish won’t stick without priming. 

To know if the paint underneath was oil-based, use the alcohol test; dampen a rag with rubbing alcohol and wipe the surface. If the paint comes off, it’s water-based. If the paint doesn’t come off, it’s oil-based. 

However, priming can be useful for water-based paints too. So, apply a water-based primer before you apply the varnish. To apply primer, use a paintbrush and apply 2 coats. Wait until the previous coat dries before applying the next one. 

Once the premier dries, clean the surface. 

3. Choose The Varnish Gloss

Choose a high-quality varnish gloss.

Choose the sheen of varnish you want to use. You can use high-gloss, semi-gloss, or satin varnish. The high-gloss varnish offers the best moisture-resistant features. It protects the wood underneath best and has a shiny finish.

The satin varnish doesn’t have a shiny finish and doesn’t protect the material underneath from water. However, satin varnish gives you a rough and dry textured finish. 

4. Apply The Varnish

Now, apply the new varnish over the old varnish.

Once you choose the sheen of the varnish, apply it over the old varnish. To apply varnish, use a paintbrush and apply light coats. 

You must apply 2 coats of varnish over old varnish. You must sand between coats of varnish, but you shouldn’t sand the final coat. 

Water-based varnish takes 6 hours to dry enough for a re-coat. While oil-based varnish dries within 24 hours. 

Sanding The Final Coat of Varnish

You must sand varnish if you apply more than 1 coat. Varnish, when dry, forms a glossy finish that won’t allow the next coat of stick. Sanding removes the glossy finish and allows the new coat to stick. 

However, you shouldn’t sand the final coat of varnish. The final coat of varnish has a thick and moisture-resistant layer that protects the material underneath from any liquid. The glossy layer also protects the material from scratches and prevents dust or dirt from getting through. 

If you sand the final coat of varnish, the varnish will lose its glossy finish and won’t protect the wood underneath. 

To sand varnish, use 220-grit fine sandpaper. The fine sandpaper will only remove the glossy finish and leave the remaining varnish on the surface. If you use rough sandpaper, you risk removing the entire old layer.

You should avoid using steel wood while sanding as it can develop rust in the finish later. 

Applying Dark Varnish over Light Varnish (or Vice Versa)

You can apply dark varnish over light varnish. However, you must sand the light varnish (to remove the glossy finish) and apply at least two coats of dark varnish.

You can skip sanding if the light varnish is water-based. That’s because water-based varnish doesn’t have a thick and glossy finish, and you can apply another coat of varnish over it without sanding.

You must apply at least 2 coats of dark varnish over light varnish to prevent bleed-through. If you apply just one coat of dark varnish, the light varnish might bleed through and mix with the dark varnish. So to avoid this, apply 2-3 coats of dark varnish. You can also apply primer to prevent bleed-through. 

If you want to apply light varnish over dark varnish, you must apply 2 coats of primer or remove the dark varnish entirely. If you don’t apply primer, the old dark varnish will bleed through the white varnish. 

Related Read: How To Paint Over Varnished Wood?

Final Words

You can apply varnish over old varnish, but you must sand and prime the old varnish first. However, to get the best result, you have to remove the old varnish and apply a new varnish. 

Leave a Comment