Can you use water based polyurethane over and oil based stain?

Water based polyurethane has wide application in paints and coatings industry. It is generally used in wood and textile products. Oil based stain is used is widely used in wood applications to enhance the colour and durability of wood. In this article, we will discuss can we use water based polyurethane over oil based stain?

Can you use water based polyurethane over oil based stain? and what precautions should be taken to apply over oil based stain?

Yes, you can use water based polyurethane over oil based stain. But before applying it over oil based stain the following precautions should be taken.

Check compatibility.

First of all, check the compatibility of water-based polyurethane over oil-based stain. This is important because if both paints are not compatible then it creates adhesion problems, surface appearance issues, and finish defects (tackiness, sagging, etc). Due to incompatibility, unwanted chemical reactions may start to proceed, and the repercussions of reactions may be dangerous.

oil based stain should be dried throughly.

Before application of water-based polyurethane over it check oil-based stain is dried or not. It normally takes 24-48 hours to dry. Well, which type of stain is applied on wood decides the drying time for it.

Sanding.

Sanding creates roughness to the surface which helps in improving the inter-coat adhesion between oil-based stain and water-based polyurethane. This mitigates the peeling and delamination of coating over the time.

Mitigation of surface imperfections.

Sanding not only smooths the surface but also mitigates surface imperfections such as brush marks, dirt, drips, and oil residues that may have occurred during the application of oil-based stain. Henceforth, mitigating imperfect surfaces makes easy job for subsequent application of water-based polyurethane coating. I believe that after the application of polyurethane, you will get a more uniform and smooth surface.

Check the quality of water based stain.

Before starting the application on a broad area, check the quality of polyurethane over oil-based stains such as drying, finish, and color.

Application.

Apply the polyurethane topcoat as per the manufacturer’s instructions. I suggest you apply the thin layers of polyurethane so that the initial coat will have sufficient drying time before the application of subsequent coats.

Sanding.

Apply at least 2-3 coats of water-based polyurethane over oil-based satin. After applying each step of polyurethane sanding the surface is a must before applying the subsequent layers. The main solvent used in water-based polyurethane is water. When we apply a coat of polyurethane some water gets absorbed into the oil-based stain. This enlarges the wood fiber ( swelling in wood). This is popularly known as grain raising. Once the polyurethane dries it creates a rough surface that needs to be smoothened. Henceforth, this is an inevitable step during the water-based polyurethane application over oil-based stain.

Cleaning.

After checking compatibility, sanding, removing surface imperfections, checking the quality of water-based stain, and finally, application of water-based polyurethane, clean the polyurethane drips, and brushes with water.

How to apply water-based polyurethane over stain?

Prepare the surface.

The stained surface should be clean, dust-free, with zero oil residue, and dry. After ensuring cleaning, a dust-free surface sand the stained surface with fine-grit sandpaper usually (220grit or more). This will help water-based polyurethane to adhere properly to stained surfaces.

Stir the polyurethane.

Before application stir polyurethane to get uniform mixing over all material. Avoid vigorous mixing, because if you mix it vigorously, bubbles will form. Once the bubbles are formed then it is difficult for us to apply them creating uneven distribution of polyurethane over the surface. This ruins the final finish.

The air bubbles entrapped in polyurethane material enlarge the surface area by creating tiny voids or pockets throughout the material. This delays the water(solvent) evaporation from the coating eventually delaying in drying of water-based polyurethanes. Hence, stir the polyurethane carefully.

Choose the appropriate tool.

Apply the first coat by using a high-quality synthetic bristle brush, foam brush, etc. Apply the coat in the direction of the wood grain to minimize brush marks. Avoid overbrushing on the surface which leads to unwanted bubble formation in the coating. The drying time for the first coat is usually 1-2 hours with DFT(Dry film thickness) of 40-50 microns. The drying time truly depends upon the temperature and humidity in the atmosphere.

Light sanding.

As I discussed earlier point water-based polyurethane creates wood graining which makes the rough surface. To avoid this light sanding is done.

Apply subsequent coats.

For this work, a maximum of 2-3 coats are needed. above same procedure should be followed for subsequent coats.

Final drying time.

After the application of all water-based polyurethane coats, let the system dry for at least 24 hours. It can be fully cured in 1 week, however, it depends upon weather and climate.

Buffing.

To enhance the aesthetic appearance of the surface buffing is done. Hence, the fully dried surface is smoothened by steel wool or an abrasive pad. Buffing is an optional step to use water-based polyurethane over oil-based stain.

How long should oil-based stain dry before applying water-based polyurethane?

Typically, you should wait for at least 24-48 hours for oil-based stain to dry thoroughly. Then you can start applying polyurethane.

Oil-based stain is dried if,

You don’t feel any smell from the stain. The coating powder will form light sanding. Remarkable gloss level difference between immediately after application and after completion of defined drying hours of oil-based stain. You don’t feel any kind of sogginess and color detach when you touch the stained oil surface. You miss the wet shiny spots on fully dried oil-based stain. The surface appears uniformly matt.

How can you determine if the polyurethane on your floor is oil-based or water-based?

Oil-based polyurethane has an amber and darker hue while water-based polyurethane has a clear appearance.

The odor of oil-based polyurethane is strong while water-based polyurethane is mild.

Oil-based polyurethane has a glossy appearance while water-based polyurethane has a milky white appearance but after application, it gives a clear appearance.

You can perform a short test in a small area, take cotton, make it soggy with mineral spirits or any solvent, and then rub it on a small area if the finish softens then it is probably oil-based polyurethane. If the floor is water-based, then there is no reaction. But during a test, the coating on the applied area may damaged.

What is the best finish over an oil-based stain?

Well, which is the best finish over oil-based stain depends upon the need of desired finish, how much protection is needed, personal preference, and financial budget. Let us discuss one by one finish which is applied over oil-based stain.

Water-based Polyurethane.

This is a fast-drying and eco-friendly finish over oil-based stain.

As it dries faster usually takes 2-3 hours, and several coats are applied in one day.

It does not emit any smell during application.

It looks milky white but after application, a clear finish is observed.

They do not stink up the house like oil-based polyurethane.

This can be cleaned easily. Hence, the labor cost requirement is low.

It enhances the durability and color of the oil-based stain.

It is thinner, and harder than oil-based polyurethane which makes it more susceptible to scratching.

Water-based polyurethane has low durability as compared to oil-based polyurethane.

I would suggest using this finish for indoor applications of the house.

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