How to Thin Latex Paint? (For a Sprayer or Paint Brush)

Latex paint has a thick flow, and thick paints are hard to apply. However, diluting them makes them lighter and easier to apply. So, how to thin latex paint?

You can thin latex paint by adding water to it in a ratio of 1:4 (1 part water – 4 parts paint). 

While diluting, you must have more latex than thinning compound (water) to prevent an inconsistent color shade. After adding the thinning compound, you must stir the mixture for 5 minutes until it has an even consistency and color. 

You can’t thin water-based paint with mineral spirits or thinning compounds containing oil. That’s because oil and water don’t mix well and can ruin the finish.

The Formula To Dilute It

You must dilute latex paint in a ratio of 1:4 (1 part thinning compound, 4 parts paint). You can also use another formula of 1/2 cup of water to 1 gallon of latex. So for 2 gallons of paint, you will need 1 cup of water (or 236 milliliters).

If you spray the paint, you must dilute it more. That’s because its flow needs to be lighter to come out smoothly from the sprayer nozzle. If you will be using a roller or brush to apply it, you don’t need to thin it as much. 

You can also find the right ratio to thin it by checking the container. Most brands include the thinning ratio on the container. 

While thinning, you must add the thinning compound to the paint, not the other way around. This means pouring the paint into a bucket first, then adding water. This way, you can monitor the color and flow. If you add the paint to the thinner, you risk over-thinning it.

Thinning Compounds To Use:

What Can You Use To Thin Latex Paint

You can use different paint thinners and solvents to thin water-based paint. Here are the top choices:

Water

You can dilute latex paint with water because it uses water as its solvent. So if you add more water, the solvent amount on the formula increases and its flow gets thinner.

However, you must add the right amount of water to avoid over-thinning it. As a rule of thumb, mix 1/2 cup of water with every gallon of paint. 

Denatured Alcohol

You can use a small amount of denatured alcohol to thin water-based paints. Denatured alcohol contains alcohol in high quantities, and alcohol can separate the pigments from the binder. So, if you use too much of it, you can ruin it.

Paint Thinner

You can use also water-based paint thinner to thin it. However, you can’t use oil-based or petroleum-distilled paint thinner because they contain oil and will ruin the flow and color shade of the finish. 

Mineral Spirits

Mineral spirits contains natural oils from trees and petroleum, so you shouldn’t use it to dilute water-based paints. If you use it, you will ruin its color and viscosity. This will make it difficult for it to stick, dry, and stay on the material. 

Lacquer Thinner

You shouldn’t use lacquer thinner as it is designed to thin lacquer, not latex paint.

If you use lacquer thinner, you risk separating the pigments. This is because lacquer thinner is made of solvents like acetone. Acetone is meant to thin the oils and pigments in lacquer stain and not water-based paints.

How To Thin Latex Paint?

Thinning water-based paint isn’t hard, but you must use the right type and amount of water.

Here are the tools you need:

  • Water-based paint thinner or water
  • A paint mixer or turning stick
  • A paint bucket
  • Rubber gloves
  • Latex paint
  • Clean rags

1. Open and Pour The Latex Paint

Open and Pour The Latex Paint

Ensure that the bucket is clean, and if there’s any residue, especially oil-based paint, you must remove it as it can affect the flow and color of the latex paint.

Once the bucket is clean, pour the water-based paint. Measure the amount you poured because you need it to calculate the right amount of paint thinner to add. 

You can also dilute it inside its container, but it’s better to use a large clean bucket because you have more space to work with.

2. Add The Needed Paint Thinner (Water)

Measure and Pour The Needed Amount of Paint Thinner

Before adding water to the container, you must measure the water you need.

To thin latex paint for a sprayer, add 1/2 cup of water to 1 gallon of it. To it for brushing or rolling, add 1/4 cup of water to 1 gallon of paint. 

If you are using a sprayer you must thin it more because sprayers can’t apply thick coatings. So, the paint must be as thin as possible without affecting its color. Rollers and brushes can apply thicker coats.

If you want to avoid brush marks, use Floetrol instead of water. Add 4-8 ounces of Floetrol to a quarter of latex paint. 

Water-based paints have different flows based on the brand and type. So if you add the required amount of water, but it doesn’t seem enough, you can add more. 

4. Stir The Mixture

Stir The Mixture Thoroughly

After you add the required amount of water, stir the mixture.

To stir it:

  1. Use a paint mixer or a turning stick.
  2. Stir the mixture for 5 minutes or until the mixture has an even flow and color.
  3. While stirring with a turning stick, ensure to press at the bottom of the container so the bottom of the paint mixes too. 

If you notice the water flowing on the paint, it means you still need to stir. You have to stir until you have an even color.

5. Test The Mixture

Test The Latex Paint

You must test the thinned latex paint on a dispensable surface, such as cardboard or paper plaster. If it has imperfections after it dries, it means you added too much or not enough water so you must stir it again.

If it has a consistent flow, dries well and fast, and the finish is smooth, you can use it. 

If You Over-thin Latex Paint:

1. The Paint Color Will Get Lighter

The color gets lighter when you add too much water to the paint. So when the paint dries, you get a lighter shade than the one you bought.

This can also make it very difficult to seal or cover existing finishes on the surface as paint bleed-through will be evident. In simple terms, over-thinning it gives you a lighter shade of color.

2. The Paint Won’t Stick Well

If you over-dilute latex paint, it will have more solvents than binders or pigments. This makes it difficult for it to stick even to a well-primed surface. As a result, its adhesion will be weak, and it will peel off eventually.

3. You’ll Experience Runs and Drips

If there’s too much solvent (water) in the formula, the paint will lose its viscosity and thickness. So, when you apply it, it will drip on the floors, especially if you apply it on a vertical surface (such as a wall). 

4. It Will Dry Too Fast

Since over-diluted paint has a lighter flow, the paint will dry fast — too fast. This means the particles won’t harden properly, and the finish won’t be durable. 

Related Read: Latex Paint Dry Time?

Final Words

You can dilute latex paint with water or water-based paint thinner. However, you must use the right amount to avoid over-thinning it. 

A good rule of thumb is to use a ratio of 1:4 (1 part water, 4 parts paint), or add 1/2 cup of water to 1 gallon of paint. 

Tony Adams
Tony Adams

Tony is a professional painter and an author of DIY Geeks. Tony has completed over 1,000 painting projects for his clients. It's safe to say he knows what he Is talking about,

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