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Can You Thin Polyurethane With Paint Thinner? (What You Need To Know)

is thinning Polyurethane with paint thinner possible

Using polyurethane paint can be a great option for many areas of your home. It is a versatile paint that covers well, lasts a long time, and looks amazing. However, there may be some materials or some areas of the home that do not need the regular thickness that come from polyurethane. They need something a little thinner, but can you use paint thinner to help with this?

Paint thinner can be used to help thin polyurethane to the right consistency that you need. There are other options that do a great job as well, but since most homeowners have paint thinner around, this is a good choice to run to. Always read the label to make sure the paint thinner is compatible with polyurethane before beginning. 

Let’s take a look at polyurethane and how paint thinners are able to help give you the exact consistency and texture that you want with this type of paint.

Related: A Complete Guide To Painting Your Own House Like A Professional

Can Paint Thinner Thin Polyurethane?

Yes, paint thinners can be used to help thin out polyurethane if it becomes too thick. However, since most paint thinners are made out of many different types of substances depending on the brand you buy, they may also have different levels of toxicity and odor. You should always check the label on the paint thinner to make sure it works well with polyurethane products before you start. Some will do fine and others will not work at all. 

As long as the paint thinner is appropriate for polyurethane, it will work perfectly. You can add in it, though do so in stages so the paint will not get too thin. Paint thinner is very effective at its job and putting too much in too quickly can leave you with a watery paint that is hard to use. 

To get the paint thinner ready to go, you simply need to open up the can of polyurethane and pour a little bit in. Do not go crazy here. A little bit at a time is plenty to help start and you can always add in more later. Stir the mixture around with a clean stick and then determine if you need to add more paint thinner or not. 

Other Thinning Agents to Use

If you have some paint thinner on hand and want to make your polyurethane thinner, then go ahead and use that. As long as the paint thinner is approved to be used in the polyurethane, you will be fine. Just make sure to read the label first. 

However, if you do not have paint thinner on hand, there are a few other options you can use to help thin out the polyurethane and get it to the right consistency that you want. These include:


Water works well if you already use a water-based polyurethane. If the polyurethane is not water-based, then you do not want to add water to it. Look on the can and follow the instructions exactly before you use this method. 

Mineral Spirits

You can also choose mineral spirits to help thin out your polyurethane. These are advantageous to work with because they do not have a strong odor with them and this makes them easy to use and pleasant. While looking on the label of the mineral spirits, you will notice they are distilled from petroleum and work as not only a thinning medium, but a milk solvent. They can easily help thin out your polyurethane and get it to the consistency that you want. 


If you have nothing else on hand when you get started, then turpentine may be the best bet. It has a really strong smell and this can be off putting to many who want to use it. However, artists know how effective this chemical is for thinning out any type of polyurethane. One thing to keep in mind with this though is to only add the turpentine into the polyurethane if you can do so outside or in a well-ventilated area. 

The Best Thinning Technique to Use

While there are many different types of thinning agents you can use with polyurethane, you need to use the right thinning technique to make sure your paint will not spoil or run into trouble. Always add the thinner in as carefully as possible. 

The best way to start this is to take out a clean stirring stick. Any type that you get from the paint or hardware store will be fine here. You do not want to shake around the can because this will add in air bubbles and makes the finish of your paint less smooth. 

Instead, slowly add in the thinner of your choice, doing so in several batches. At the same time, use the clean stick to slowly mix the thinner with the polyurethane. A figure eight motion is the best way to do the stirring to get everything mixed in well. As you go, scrape any thick material from the sides and bottom of the can. Continue this until the polyurethane has a texture that is uniform. 

Continue to mix in some more thinner as well. A little at a time is plenty here. If you put too much of the thinning agent in at a time, it can make the polyurethane too watery and it won’t work as well as you want. Doing so slowly helps you get the perfect texture each time.

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