How to Thin Water Based Latex Paint for Spray Gun?

how to thin water-based paint for spraying

Using a spray gun to repaint interiors or exteriors is a fast and efficient process.

However, you will need to thin the water-based paints that you want to apply.

Thinning the paint is cheap and fairly easy to do if you understand how to get the right consistency or viscosity.

Of course, using a spray gun will mean understanding the meaning of water-based paint, why it needs to be thinned, and how to thin it properly.

Let’s address all your questions one by one in the article below…

What is Water-Based Paint?

For indoor and outdoor painting, there are two basic types of paints, alkyd, and latex.

Alkyd paint is oil-based which means that it uses a petroleum base as its solvent. Latex is water-based, which means that it uses water as its solvent.

Until recently, alkyd paints were recommended for spray guns because they are thinner compared to water-based paints.

They flow through the spray evenly and because they take longer to dry, they did not clog the nozzle of the sprayer.

However, advances in water-based paints combined with the concern of using petroleum-based paints, especially indoors have led to more people using water-based paints for spray guns.

Keep in mind that latex and acrylic paint is the same thing as they are both water-based products.

You can use the paints the same way and thin them with water when you need to run them through a spray gun.

Why Do You Need to Thin Water-Based Paint?

Although it may seem from the description that water-based paint should have no issue with spray guns, the truth is that you will need to thin the paint for it to work properly.

Why you may ask? The reason is simple.

Because this type of paint is too thick to be used with a spray gun.

Water-based latex paints are primarily designed for the brush or roller, not to be sprayed.

Especially if you are using an HVLP sprayer or any other fine finish gun – it will need thin paint for it to work properly.

While working with spraying guns, you will need to take a little time to thin the paint so that it will not clog your spray gun.

You can see by the viscosity levels of water-based paints which tend to be quite thick to allow the paint to stick to the surface when using a brush or roller.

If you think that the extra time may not be worth it, remember that applying paint with a spray gun tends to be faster and can be done evenly.

So it may make up for the time you spent diluting the paint.

painter thinning water based paint

How Do You Thin Water Based Latex Paint for Spraying?

It’s a fairly simple process to thin this type of paint for sprayer guns like Wagner HVLP, but you will need a clean bucket and access to water to do the job.

The first step is to gather all the paint that you are going to use that day.

Any excess paint can stay in the cans until the next day.

Once you have gathered the paint, start by following these paint thinning steps:

Step 1- Stir and check the paint thickness

Before you open up your paint can mix it thoroughly by shaking it with both hands.

This step is more important if you are using old leftover paint that’s sitting for a long time in your storage.

Now open the can and stir the paint using a wooden paint stick. Make sure you mix the paint in a circular motion so that no paint material is left settled at the bottom of the container.

After thorough stirring, slowly lift the stir out of the paint and notice how the paint is dripping off.

This will help get an idea about the thickness of your paint and the amount of water you will need to mix for getting the right viscosity.

Step 2- Pour the paint into a clean 5-gallon bucket

Now for thinning the paint, start by pouring a small amount of paint into your 5-gallon bucket.

You can take a smaller one if you need to thin a small amount for spraying a smaller area.

Step 3- Add ½ cup of water for each gallon of paint

Next, mix in some water slowly.

Typically, you should be using about 1/2 cup of water for every gallon of paint.

This will help you achieve the desired consistency.  

If required you can always add a bit more water.

And if you happen to add more water than required – do not worry.

You can either add more latex paint or allow the paint to get thicker for some time.

IMO, if you are using high-quality latex paint, it will most likely become thicker and will need more water.

Step 4- Use stick or drill attachment to mix paint and water together

As you add the water to the paint, be sure that you stir the paint slowly using a stick or a stirrer drill attachment.  

After every 10 to 15 seconds, check the thickness of the paint by pulling out the stick and noticing how well it’s dripping.

Once you achieve the right consistency make sure you test for the viscosity to rest to ensure that the paint does not clog your HVLP paint spray gun.

Step 5- Run paint through a funnel to test the desired viscosity

For testing the viscosity, you’ll want to thin the paint until it flows freely through the funnel.

You can use a paper funnel if you want or a plastic one that can be washed so the paint does not sick.

If it does not flow freely, add 1/8th of a cup and mix thoroughly again.

Repeat until the mixture flows freely through the funnel.


Once you have completed the task, remember how much water you used so you can add that amount the next time you need to thin the paint.

The temperature will make a difference in the viscosity of the paint.

So, the warmer the temperature, the more the paint will flow through the sprayer.

However, you will want to keep the temperature below 90 degrees F or you run the risk of the paint drying too fast and cracking after it dries.

Keep in mind that the characteristics of the latex paint will change when you add more water.

This means that the drying time may be different, but more importantly, the color may change, so you will need to be aware that when thinning the paint, it may not be quite the same shade or depth of color.

Also remember, that different sprayer machines (from different manufacturers and of different styles) will require a different thickness of paint.

So, it’s good to check the instructions manual, that comes with your sprayer machine, if it has some tips to achieve the right consistency.

best medium to thin water-based paints

What is the best medium to thin water-based paint?

Your best bet to thin water-based latex paints for sprayer guns is water.

Make sure that you stray from using any other medium, especially when you are using fine spray guns.

Many people make mistakes by choosing products such as Floetrol for thinning the paint.

But keep in mind, it’s not a solvent to be used for thinning water-based latex paints for spray guns.

Floetrol is basically a paint conditioner (meant to condition the paint) and it works differently than water.

Can you use paint thinner to thin latex paints?

Alcohol or any other oil-based solvents (like paint thinners, and mineral spirits) are meant to thin oil-based paints and not water-based latex paints.

If you try to add petroleum-based products to thin latex paint, it will only “gel” the paint thereby creating a messy product that is unusable.

In a pinch, if you don’t have water available you can use rubbing alcohol or isopropyl alcohol (IPA) for latex.

Even better, if you want to use it, you should first check the manufacturer guidelines on the paint tin before thinning.

If it allows using alcohol make sure that you do not use water with alcohol.

Tips for Using Your Wagner Spray Gun with Water Based Paints

Once you are ready, you can load the spray gun with the amount of paint that you want to use.

Depending on the design of the gun, you may have to put the paint into a separate container that loads the gun.

When you are ready to spray, hold the gun several inches from the surface and apply nice, even coats by slowly going back and forth or up and down.

You’ll want an even layer to avoid thick spots that may distort the appearance of the paint on the surface.

It does not take long to get the right technique down, so once you are comfortable with spraying the paint, you should be able to complete a single coat in a relatively short time.

You may want to practice on scrap wood or another surface to get the technique right and understand how the paint is properly applied.

This will also let you know if the paint is leaving the spray gun properly or needs to be thinned even more.

Once you have completed a day’s work, clean the spray gun nozzle of all paint.

This will help keep it from clogging as you load up the paint for the next day’s work.

The Bottom Line

Professionals recommend spraying latex paints for the best possible protection and outcome on your project.

However, spraying water-based paints involves first thinning out and then using a spray applicator like a paint sprayer.

The advantages of using a spray gun are considerable when you can properly thin the water-based paints (like latex, polyurethane, etc) that are being used.

Remember to thin out water-based enamel paint slowly, so you can apply it evenly to the surfaces both inside and outside your home.

Simply stick to this professional paint thinning guide to ensure a healthy and shiny project that stays clean and polished for years after your project finishes.

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