Can You Put Thompson Water Seal Over Stained Wood?

Wood stains give amazing color but no waterproofing, so the finish is prone to water damage. But is it possible to make wood stain waterproof by applying Thompson water seal over it?

You can apply Thompson water seal over stained wood. This is a great hack to protect the wood from water damage and mold growth on wood. However, whether this is a good idea or not depends on the type of wood stain on the wood.

Thompson water seal can go over water-based and some oil-based wood stains with proper preparation. However, you shouldn’t use the water seal on varnish or gel stains because it will not stick.

So, what type of Thompson water seal can you apply over stained wood and how do you apply the sealer perfectly? The answers to these questions and more are discussed in detail below. Let’s dive in.

Do You Have To Remove Stain Before Applying Thompson Water Sealer?

You don’t have to remove the wood stain before applying Thompson water sealer because Thompson water sealer sticks to wood stains. As long as the wood stain finish is properly cleaned and sanded, you can apply the water sealer over it.

You should not apply Thompson water sealer on a sealed stain, varnish stain, and gel stain. All of these finishes have water resistance and a high volume of oils. As such, these stains will not accept the Thompson water sealer properly. If you have a sealed stain, you need to remove it before applying the water sealer.

When you want to apply Thompson water sealer, you can apply the sealer on bare wood and already-stained wood. For bare wood, you can apply the water sealer directly but for already stained wood, you’ll need to inspect the type of wood stain before applying the water sealer.

If the wood stain is waterproof or water-resistant, you’ll need to remove the top coat before applying the Thompson water sealer. This is because waterproof and water-resistant wood stains especially the oil-based types don’t accept top coats properly. If you apply the Thompson water seal directly on a waterproof or water-resistant wood stain, the sealer will not stick. Asides from this, the finish will develop problems later such as peeling and chipping.

However, if the existing wood stain is water-based or oil-based, then you can apply the Thompson water sealer directly over the wood stain without removing it. In this case, sanding the wood stain with fine sandpaper is enough to prep the stain before the water sealer is applied.

How To Apply Thompson Water Sealer Over Stained Wood?

There are steps to follow when you want to apply Thompson water seal over already stained wood. If you don’t follow these steps, you’ll struggle to get a good and clean finish. Luckily, this guide reveals how to apply Thompson water seal on stained wood in 5 simple steps. But first, we’ll need a few tools and supplies:

  • Thompson water seal
  • An airless paint sprayer
  • Sandpaper of different grits
  • Masking tape
  • Microfiber cloth
  • A pair of gloves
  • Denatured alcohol
  • Breathing protection
  • Drop sheets

Here is a guide on how to apply Thompson water sealer over stained wood.

1. Prep The Work Area

Prep The Work Area

The first step is to prep your work area. This is important if you want to get a perfect finish. Start by removing all items on and around the wood to be sealed. If you have items or furniture that you can’t remove or lift, you should cover such items with drop sheets.

After removing and covering the items that you don’t want to seal, you should wipe and clean the stained wood. Use a lint-free rag for this.

The purpose of wiping and cleaning the wood is to remove dust nibs and stains on the wood stain finish. After cleaning, use masking tape to demarcate different parts of the wood so you can work in sections.

2. Wipe The Wood Stain With Diluted Alcohol

Wipe The Wood Stain With Diluted Alcohol

The next step is to degrease and remove oils on the wood stain. To do this, mix equal parts of denatured alcohol with water. You can also use mineral spirits if you don’t have denatured alcohol. Use a microfiber cloth and the diluted solution to wipe down the wood stain. Use only a little of the solvent so the wood stain isn’t damaged.

The next thing to do is to inspect the finish using the water test. This is to know if the finish has an existing sealant or not. If the wood stain finish has an existing sealant, you need to strip it with a chemical-based paint stripper. Find out more about the water test below in this article.

3. Sand The Wood Stain

Sand The Wood Stain

After removing the existing sealant, you should sand the wood stain with 320-grit sandpaper. If there was no sealant, you should sand directly with 320 or 400-grit sandpaper. When you are done sanding, wipe off and remove the dust.

The next step is to prep the Thompson water sealer. To do this, follow the manufacturer’s instructions. You might need to stir or shake the Thompson water sealer before application.

4. Apply The Thompson Water Sealer

Apply The Thompson Water Sealer

The final step is to apply the water sealer. You can do this using a paintbrush, roller, or paint sprayer but the best method to use is a paint sprayer, preferably an airless or HVLP paint sprayer.

To use the sprayer, assemble the tools, prime the sprayer, and apply the Thompson water sealer on the wood stain. You can apply up to two thin coats of the water sealer for good coverage and protection.

After applying the sealer, leave it to dry for at least 48 hours before normal service of the surface is resumed.

Next, let’s find out how long it takes for wood stain to dry before Thompson water seal can be applied.

How Long Should Stain Dry Before Applying Thompson Water Seal?

You should let the wood stain cure or dry fully before applying the Thompson water seal. This is because all the moisture content in the wood stain needs to have been evaporated before Thompson water sealer can be applied.

If you apply the water sealer over a damp or fresh wood stain, the whole finish will be ruined. It takes an average dry time of 24 hours for water-based wood stains to cure but oil-based wood stains take about 48 hours. Only when the wood stain has cured should you apply a sealer coat.

Many DIYers get confused when applying Thompson water sealer over a wood stain. This is because Thompson water sealer can be applied over damp wood but the sealer shouldn’t be applied over a damp wood stain.

When wood is damp, you can apply the Thompson water sealer because the moisture in the wood can’t damage the water sealer. However, this is a very different case when dealing with stained wood.

Wood stains don’t just contain water. These wood stains contain oils, solvents, pigments, and additives. Some of these compounds in the wood stain can ruin the Thompson water sealer. So you need to allow all of these solvents, additives, and moisture in the wood stain to evaporate before applying the stain. On average, allow the wood stain to dry for 24 – 48 hours before applying Thompson water sealer.

How To Know if Stained Wood Needs Sealing?

To know if stained wood needs sealing, you should use the water test. To do this, sprinkle some water directly on the stained wood and wait a few minutes.

If the water is absorbed into the wood stain finish, then it means the stained wood needs sealing. If the water beads on the wood stain finish or isn’t absorbed in the wood, then the wood stain doesn’t need sealing.

Here is how the water test works. If the water is absorbed in the wood stain, it means that there is no waterproof coat on the wood stain. Since there is no waterproof coat on the wood stain, it means that the finish can be easily affected by moisture or rainfall.

In this case, the wood stain needs a sealant so it can be waterproof. However, if the water wasn’t absorbed in the wood, it means that there is a waterproof coat on the wood stain. In this case, you don’t need another water sealer because the wood stain is already waterproof enough.

Can You Use Water-Based Thompson Water Seal Over Oil-Based Stained Wood?

You can use a water-based sealer like Thompson water seal on oil-based stained wood. However, the oil-based stain needs to have cured before you apply the Thompson water sealer. Also, you need to wipe down the oil-based stain with a mix of mineral spirits or denatured alcohol and water.

When the oil-based stain is dry, you should then scuff it with 320-400 grit sandpaper before applying the water-based Thompson water seal.

Oil-based stains and water-based sealers aren’t compatible when either finish is wet. So, you need to allow the oil-based stain to dry fully before applying the water-based sealer. If you apply the sealer over the oil-based stain before the oil-based stain has cured, the oils on the stain will affect the water-based sealer and the result is poor adhesion between both coats. You should know that it can take over 2 weeks for an oil-based wood stain to cure enough for a water sealer.

When the stain has cured, you should wipe it with diluted mineral spirits to remove grease and oily residue. When the stain is dry, sand it and apply the sealer.

Can You Use Oil-Based Thompson Water Seal Over Water-Based Stained Wood?

Thompson water seal penetrating timber oil can be used over water-based stain as long as the wood stain is fully dry. This is because water-based stains don’t have any water-resistant top coat or additives that repels paints.

Also, water-based wood stains accept wood sealers and top coats well so an oil-based Thompson water seal will work fine on a water-based stain.

To improve adhesion between the water-based stain and the Thompson water seal penetrating oil, you can scuff the water-based stain with 320-grit sandpaper before applying the water seal.

Final Words

In summary, Thompson water sealer can be applied over already stained wood. You just need to find out what kind of wood stain is on the surface to know how to prep it for the water sealer.

For water-based and oil-based wood stains, you need to clean the stain and sand with fine sandpaper before applying the water seal.

For gel stains, varnish, and other water-resistant stains, you need to remove the top coat of the stain before applying the water seal so the coats can stick. The best way to apply Thompson water sealer on stained wood is to use an airless paint sprayer.

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