How to Thin Water Based Latex Paint for Spray Gun?

Using a spray gun and water-based paints to repaint your interiors or exteriors is a fast and efficient way to update your home looks.

However, to get the right consistency or paint viscosity, you will need to thin the water-based paints that you want to apply.

Thinning the paint is cheap and reasonably easy to do. But understanding why water-based paints need to be thinned in the first place and how to thin them correctly is crucial before starting your project.

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

What is Water-Based Paint?

There are two basic types of paints for indoor and outdoor painting: alkyd and latex.

Alkyd paint is oil-based, using a petroleum base as its solvent. Latex is water-based, which means 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 do not clog the sprayer’s nozzle.

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, acrylic, and chalk paint are all water-based products, which means you can use the paints the same way and dilute 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 (in its original form) 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 fine finish gun – it will need thin paint to work correctly.

This means if you plan to work with latex paint in your spraying guns, you will need to take a little time to thin the paint so that it will not clog your spray gun.

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How Do You Thin Water Based Latex Paint for Spraying?

It’s a fairly simple process to thin water paints for your Wagner HVLP sprayer gun if you have a clean bucket and access to water.

The first step is to gather all the paint you will 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 steps:

Step 1- Stir and check the paint thickness

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

This step is even 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 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 you get an idea about the thickness of your paint and the amount of water you will need to mix to get a suitable viscosity.

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

For thinning the paint, pour a small amount into your 5-gallon bucket.

You can take a smaller bucket or a plastic cup 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 some water slowly into the bucket.

Typically, you should be using about 1/2 cup of water for every gallon of paint. But, if required, add a bit more water until you achieve the desired consistency.

Do not worry – if you happen to add more water than needed. You can either add more latex paint or allow the paint to get thicker for some time.

If you will be using high-quality latex paint, it will most likely become thicker and need more water.

Step 4- Use a 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, test for the viscosity to ensure that the paint does not clog your HVLP paint spray gun.

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

For testing the viscosity of thinned paint, use a paper funnel or a plastic one that can be washed and reused.

Run the paint through the funnel to check the consistency.

If it doesn’t pass freely and seems to clog the funnel, add 1/8^th of a cup of water again and mix thoroughly.

You should keep thinning the paint with a small amount of water until it becomes thick enough to flow 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.

A Few Important Things to Note:

1- Do not use paint thinner to thin latex paints

Alcohol or 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, creating an unusable messy product.

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

But to be safe, first, check the manufacturer’s guidelines on the paint tin before thinning. If it allows using alcohol, do not use water and alcohol both at the same time.

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

This means you should stray from using any other medium when using fine spray guns.

Many people make mistakes by choosing products such as Floetrol for thinning the paint. Keep in mind it’s not a solvent to be used for thinning water-based latex paints for spraying.

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

3- Characteristics of the latex paint will change when you add more water.

When you add water, the drying time of the paint may get affected, but more importantly, the color may change.

So you must be aware that after thinning the paint, it may not be quite the same shade or depth of color you picked.

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

Due to this reason, 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 risk the paint drying too fast and cracking after it dries.

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

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.

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Tips for Using Your Wagner Spray Gun with Water-Based Paints

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

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

Next, practice on scrap wood or cardboard piece to get the technique right and understand how the paint is applied.

This will also let you know if the paint leaves the spray gun properly or needs to be thinned further.

When ready (and pretty confident), hold the gun several inches from the surface to apply nicer-looking, even coats by slowly going back and forth or up and down.

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

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

Once you have completed a day’s work, clean the spray gun nozzle of all paint to help keep it from clogging as you load up the paint for the next day’s work.

The Bottom Line

The advantages of using a spray gun are considerable when you can adequately thin the water-based paints (like latex, acrylic, chalk, and even polyurethane) using water as a medium.

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