Mixing Latex Paint With Polyurethane (Here’s What To Avoid)

Mixing different types of paint is a common practice, especially with latex paints. But can you mix latex paint with polyurethane?

You can mix latex paint with water-based polyurethane because they use the same paint solvent (water). However, you can’t mix latex with oil-based polyurethane because of the different paint solvents. 

Mixing latex with polyurethane is done to give the polyurethane a color tint. Being a clear coat, polyurethane doesn’t have paint pigments on its formula; this means the polyurethane finish has no color. So, if you mix latex and polyurethane, you will get a durable colorful finish. 

Don’t Mix Oil-Based Polyurethane With Latex Paint

You can’t mix oil-based polyurethane with latex paint because they have a different paint solvent (base). Latex paint uses water as its paint solvent, while oil-based polyurethane uses natural or synthetic oil.

Polyurethane and latex paint dry through evaporation. The paint solvent of latex paint and polyurethane must fully evaporate for the coating to become dry. Since water evaporates faster than oil, latex paint and polyurethane have different dry times.

If you mix latex paint with polyurethane, the mixture won’t dry properly. Some parts (spots) of the mixture will fully dry, while the other parts will still be wet. This leads to paint cracks. 

Also, the flow of the mixture will be inconsistent since oil and water don’t mix. So, you must avoid mixing latex paint with oil-based polyurethane. Only mix latex with water-based polyurethane. 

How To Mix Latex Paint With Polyurethane?

Mixing latex paint with polyurethane isn’t hard. But, you need the right steps and tools to do it.

Here are the tools you need:

  • A Can Of Latex Paint
  • Water-based Polyurethane Finish
  • A Clean Bucket
  • Water
  • Paint Mixer Or Turning Stick
  • A Measuring Cup

Note: You must mix latex paint with water-based polyurethane only. The finish won’t stick or dry if you mix latex paint with oil-based polyurethane.

1. Pour Polyurethane Into a Clean Bucket.

First, open the lids of the latex paint and water-based polyurethane. 

Pour the required amount of water-based polyurethane into a clean bucket. You can use a measuring cup to measure how much polyurethane you are pouring. 

Water-based polyurethane must be poured into a clean bucket first. That’s because you are tinting polyurethane and not the other way around. If you pour latex first, the water-based polyurethane will act as a paint thinner and thin latex paint. 

3. Add Latex Paint

You must mix latex and polyurethane with a ratio of 2:1 (2 parts polyurethane to 1 part latex paint). If you don’t want a bright finish, use 1/2 part of latex instead of 1 part. 

The main purpose of latex paint is to give polyurethane a colorful finish. The mixed polyurethane will have the same color shade as latex. So, use latex paint with a color shade you want the finish to have. Due to the clear coat finish of polyurethane, the mixture (polyurethane and latex) will have a brighter color than the original latex. 

If you want to mix two or more colors of latex paint with polyurethane, mixing the latex paints first in a different container is better. Once you mix the latex paint color, apply the mixture to the polyurethane bucket and mix them again.

4. Stir The Mixture

Once you add the required amount of latex paint to the water-based polyurethane, stir the mixture. 

To stir the mixture: 

  1. Use a paint mixer or turning stick,
  2. Ensure the turning stick touches the base (bottom) of the container while stirring. 
  3. If you use a turning stick, stir for 15 minutes. If you use a paint mixer, stir for 5-7 minutes.
  4. You can add drops of latex paint to the mixture while stirring. 
  5. Once the paint has a consistent color and flow, stop stirring. 

5. Test The Paint Mixture

You must test the mixture of latex paint and polyurethane on a dispensable item. Testing will show if the mixture has a consistent flow and color and if it dries.

Using a paintbrush, apply the mixture to cardboard. If the mixture doesn’t dry, turns sticky, or has inconsistent color, you must re-mix it or add more latex paint. If the mixture dries properly and has a consistent color shade, you can use it. 

Applying Polyurethane Over Latex Paint

You can apply polyurethane over latex paint to increase the durability of the finish. Latex paint being water-based, doesn’t have a moisture-resistant or durable finish. So, you must seal latex paint to increase its durability. 

When dry, polyurethane forms a glossy moisture-resistant finish. This glossy finish will protect the latex paint from moisture, water, scratches, and damage. 

Applying polyurethane (or a sealer) over indoor latex surfaces is optional. However, sealing latex paint with polyurethane is necessary for outdoor surfaces. That’s because latex paint isn’t formulated with additives that protect the finish from outdoor weather elements. 

You can apply any type of polyurethane over latex. This includes water-based, oil-based, and exterior polyurethane. 

Applying Latex Paint Over Polyurethane

You shouldn’t apply latex paint over polyurethane. That’s because polyurethane has a glossy finish that repels liquid, including paint. So, if you apply latex over polyurethane, the latex paint won’t stick and will turn tacky.

For latex paint to stick, the paint must penetrate the surface. But, since polyurethane forms a glossy layer over the surface, the latex paint can’t penetrate the polyurethane coating, so it won’t stick. Also, polyurethane has a glossy finish, which means the latex paint will slide off the finish without having time to stick. 

The type of polyurethane doesn’t matter; latex paint won’t stick over water-based, oil-based, or exterior polyurethane. The only way to use latex paint over polyurethane is to sand the polyurethane or remove it completely, then apply latex paint.

Final Words

You must mix latex paint with water-based polyurethane only. That’s because they have the same paint solvent (water), so they are compatible. The best way to mix latex and polyurethane is to use a ratio of 2:1 (2 parts polyurethane to 1 part latex paint). 

You shouldn’t mix latex paint with oil-based polyurethane. That’s because oil-based polyurethane uses oil as its solvent, while latex paint uses water. And, water and oil solvents don’t mix. 

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