How to Thin Latex Paint for Spraying, Brushing, and Rolling

To thin or not to thin, that is the question. The answer? Thin latex paint if the manufacturer provides directions and it benefits your project. Paint formulas are carefully calculated to provide specific results, so changing paint’s physical makeup by thinning can void warranties and alter product performance if not recommended by the manufacturer.

Read on for pro tips about why and how to thin latex paint and what products to avoid from two paint industry pros Rachel Otto from Fleury Lumber and Shayne Pancione from Pancione Painting Plus.

What Is Latex Paint

Latex paint is a water-based paint used for interior and exterior applications. Available in various sheens from flat to high gloss, latex paint is a durable and versatile paint product easily applied with a brush, roller or air sprayer.

Latex paint can be used on a variety of surfaces, including interior drywall, wood and plaster, as well as exterior concrete, siding and stucco. The synthetic resins in latex paint create a flexible surface that resists cracking and withstands temperature changes.

Unlike oil-based paint, latex paint only needs soap and water to clean up.

What Is Paint Thinner?

Paint thinner is a petroleum-based solvent used to thin and clean oil-based paints. Products labeled as “paint thinner” are typically mineral spirits, a lower odor and less toxic (when compared to other paint-thinning solvents), such as liquid solvents. Other paint-thinning options include turpentine, acetone and naptha.

While most paint thinners are used with oil-based paints, “there are some formulated to be used with latex,” Otto says. “Read the label to see if it’s compatible.”

Why Thin Latex Paint?

There are a few reasons why you might choose to thin latex paint.

If using a sprayer, thinning latex paint can prevent a clogged spray nozzle. “Follow your sprayer’s operating instructions,” Otto says, “These will include thinning ratios.”

Thinning also improves the flow and leveling ability of paint, which can reduce brush strokes and provide a smoother finish.

Thinning can also change the look of paint for specialized projects. “If you’re trying to get a distressed look when painting furniture, you can thin it,” Otto says.

Finally, slightly thinning paint can extend its coverage area. “It may make the color a little different,” Otto says, “but adding water will make it go a little further.”

How to Thin Latex Paint

Different methods and products are used to thin latex paint depending on the application method, but there is one universal step. “Make sure it’s very well mixed before attempting to apply it,” Pancione says. “This applies to brush, roller or spray.”

Also, follow the paint’s technical data sheet or label for recommended thinning parameters. “If it says, ‘Do not thin,’ don’t thin it,” Otto says. “If you do, the paint can crack, peel or not adhere properly to the surface.”

For Spraying

Follow the sprayer and paint manufacturers’ instructions for thinning paint when spraying. Typically, this will be done with clean, room-temperature water, a stir stick, a bucket and a measuring cup.

First, stir the latex paint thoroughly. Use a measuring cup to measure paint and water ratios in a clean bucket. Use a stir stick to mix thoroughly.

For Brushing

“Some paints are thicker, which can make application difficult,” Otto says. In this case, add a couple of ounces of water to make brushing easier (if allowed by the manufacturer).

Mix and pour paint into a clean bucket. Add water an ounce at a time until the desired consistency has been reached.

Synthetic products, like Floetrol, can also be added to paint. “This is designed to make the paint flow smoother, level out better and avoid leaving brush strokes or roller marks,” Pancione says. It makes brushing in trim a breeze.”

For Rolling

Follow the same thinning instructions for brushing and rolling. Adding Floetrol when rolling can minimize lap lines.

However, Otto doesn’t recommend thinning with water when applying latex paint with a roller. “It doesn’t give the look the manufacturer intends and can leave streaks,” she says.

FAQs

Can you thin latex paint with water?

Yes, you can thin latex paint with water (if it is recommended by the manufacturer). Do not use solvent-based products to thin latex paint.

Is acetone a paint thinner?

Yes, acetone is a type of solvent-based paint thinner, but it is better used to clean up paint than to thin it.

“Acetone is more for removing paint,” Otto says. “It can cause paint to separate if added as a thinner.” Acetone should not be used to clean water-based paint.

Can paint thinner remove paint?

Yes, paint thinners can clean oil-based paint from paint tools and surfaces, but it is most effective when the paint is still wet. For dried oil-based paint, acetone is the only paint thinner that could effectively remove it, but typically, this is a job left to stronger stripping products.

“Just be careful and use paint thinner in a well-ventilated area and wear a mask and gloves,” Otto says. “The fumes can be hard on the lungs if breathed.” Solvent-based paint thinner is not effective at removing water-based paint.

Does paint thinner ruin paint?

It depends on the paint. Adding a solvent-based paint thinner to latex paint will ruin it. However, paint thinner will not damage oil-based paint if added in small amounts.

About the Experts

• Rachel Otto is the paint department manager at Fleury Lumber in Easthampton, Massachusetts, specializing in Benjamin Moore products. She has 10 years of industry experience.
• Shayne Pancione is the owner of Pancione Painting Plus, a full-service residential and commercial painting company in Easthampton, Massachusetts. He has over 25 years of experience in the trade.