Can You Mix Polyurethane With Stain?

In most cases, wood stain cannot be applied over polyurethane. Applying polyurethane to wet stain leads to discoloration and streaking. However, by following the steps below you can mix polyurethane with stain.

There are dozens of brands and several formulations of polyurethane and stain available at most home stores. Understanding how to differentiate among your options is key to successfully mixing polyurethane and stain.

Types of Polyurethane

There are two primary types of polyurethane: water-based and oil-based. Each type has pros and cons.

Water-based polyurethane dries more quickly than oil. It also emits fewer harmful volatile organic compounds (VOCs). Fewer VOCs makes water-based polyurethane preferable in cases where it will be applied indoors or in poorly ventilated spaces.

Improved water-based polyurethane formulas mean that many water-based polyurethanes are as durable as oil-based polyurethanes.

Oil-based polyurethanes dominated the market for much of the 20th century. Oil-based polyurethane dries slowly but leaves behind a supremely glossy and durable coat.

Woodwork coated in oil-based polyurethane also holds up well in heavily trafficked areas. This makes it ideal for doorways, kitchens, and trimwork.

Types of Stain

There are three common formulations of wood stain. Like polyurethane, water-based and oil-based stains are popular. The characteristics of these two types are similar to polyurethane as well.

Water-based stain tends to have lower VOCs and to dry more quickly while oil-based stain is more commonly found in older homes and has been more reliably durable than water-based stain.

The third type of stain that is gaining popularity is not actually a “stain” at all, though it is branded as such. Gel stains can be applied to the surface of finished wood unlike traditional stains.

Gel stains form a new surface coat on top of underlying finishes. Traditional stains penetrate into open pores of wood to alter the wood’s color. 

How to Mix Polyurethane with Stain

Given that there are two dominant forms of polyurethane, water-based and oil-based, and three common types of stain, can they be combined? The short answer is yes, but there are several caveats.

1. Oil and water do not mix well – ask a chef, mechanic, or a painter. When mixing polyurethane and stain you must be sure to only mix water-based stain and water-based polyurethane. Or conversely, only mix oil-based polyurethane with oil-based stain.
2. Gel stains are not commonly mixed with polyurethanes. If gel stain is all you have on hand, you should test a mixture on a piece of scrap wood before applying it to your project.

With that in mind, it’s time to move on to calculating mix ratios.

Selecting Mix Ratios

There is no standard ratio for mixing stain and polyurethane. Adjusting the ratio in either direction alters the outcome. Polyurethane tends to be thicker than stain, so it can be hard to know how much you need. Too much stain can drastically thin the polyurethane.

Mixing at a lower stain ratio, like 1:3 (1 part stain to 3 parts polyurethane) will give you more control over the finished product. Applying layers of a 1:3 combination will darken the wood with more control than with a 1:1 mixture. A mixture that is half polyurethane and half stain will darken or stain the wood more than a 1:3 mixture.

If you take the time to try a couple different ratios prior to applying the mixture of polyurethane and stain to your project, you can complete the project in fewer steps. The benefits of preparation and testing often trump forging ahead.

Step-by-Step Guide to Mixing

Combining polyurethane and stain is straightforward. Remember to only mix water-based polyurethanes with water-based stains and oil-based polyurethanes with water-based polyurethanes.

To create your own polyurethane-stain mixture:

1. Prepare an easy-to-clean work area.
2. Place a drop cloth or plastic sheeting beneath the area in which you will combine the products.
3. Find a clean can or painter’s bucket in which to combine your polyurethane and stain. The lighter or clearer your chosen vessel is, the easier it will be to determine when the polyurethane and stain have fully combined.
4. Determine the ratio of polyurethane to stain that you wish to achieve. 1:3 and 1:1 ratios are the most common. 
5. Open both your polyurethane and stain.
6. Stir both products thoroughly as recommended by the manufacturer. This often requires stirring with a clean paint stick for two to three minutes.
7. Pour necessary amounts of polyurethane and stain into your clean can or painter’s bucket to achieve your desired ratio.
8. Mix thoroughly until uniform coloration is achieved and there are no swirls of stain suspended in the polyurethane.

Tip: Using a spout attachment makes pouring carefully easier and can make cleanup a cinch. Using a scale can help to ensure that you are adding the exact right amount of polyurethane and stain. When mixing small test batches, use a kitchen scale.

As an example, if you want to test a 1:3 stain-to-polyurethane ratio, add 20 grams of your stain to 60 grams of polyurethane. If you are satisfied with the results of the ratio after applying it to a test piece, it is easy to scale up the ratio to complete your project.

Combining Polyurethane and Stain

Mixing the correct type of polyurethanes and stains together has a few advantages, especially with oil-based polyurethanes and stains.

1. Reduce sanding: combining your polyurethane and stain can drastically reduce the amount of sanding needed.
2. Reduce time: applying stain and polyurethane separately can add days to a project. You must wait until each coat of stain and each coat of polyurethane is dry before applying new coats. Each coat should also be lightly sanded with fine grit sandpaper, then wiped down.
3. More efficient: combining your stain and polyurethane is a more efficient way to move through the drying, sanding, and wiping cycle. Recognizing this efficiency has led many manufacturers to sell cans of premixed stain and polyurethane.

Issues with Mixing Poly and Stain

There are a handful of issues to watch out for when creating custom polyurethane and stain mixes.

• Be sure not to go too far in either direction with your combination ratio.
• Too much stain will decrease the protection provided by the polyurethane.
• Diluting the stain with too much polyurethane will make the stain’s effect on wood barely noticeable.
• Do not combine water-based polyurethane or stains with oil-based polyurethane or stains.

There can be issues applying your mixture to wood already coated with polyurethane. Polyurethane can bond to lightly sanded polyurethane, but stain cannot adhere to polyurethane. If you are trying to apply a mixture to wood that is already coated with polyurethane, the ratio of your mixture should have more polyurethane than stain.

Finish with Polyurethane

Combining polyurethane and stain is a great way to fast track your project. Each layer will darken the color of your wood, highlight its grain pattern, and add protection. I strongly recommend lightly sanding with fine grit sandpaper (#220) between each coat. 

After you have applied the desired coats of your combined polyurethane and stain, you should finish with at least one coat of polyurethane that matches the polyurethane used in your mixture. This final coat of polyurethane will seal the stain you have applied and apply an added layer of protection from dents, dings, water, and stains.

Conclusion

It is possible to combine polyurethane and stain. There are a few crucial rules that must be followed. Most importantly do not mix oil-based polyurethanes or stains with water-based polyurethanes or stains. Carefully measure your mixtures to ensure consistent, reproducible results. Finally, applying any finishing coats to your woodworking projects requires a properly prepared work space and wood to receive its finish well.