How to Thin Latex Paint for HVLP

HVLP sprayers are often used to apply thin liquids such as lacquer, but with proper preparation, they can also spray latex paint. In this article, learn why you need to thin latex paint before using it in your HVLP sprayer, what to use to thin it, and get step-by-step instructions for latex paint dilution. 

Why Do I Need to Thin Latex Paint for HVLP Sprayers?

The purpose of high-volume, low-pressure (HVLP) paint sprayers is to turn fluid into a fine, sprayable mist. This is called atomization. Thicker fluids, like latex paint, are harder to atomize than thinner liquids. 

With poor atomization, a range of difficulties arise. The paint can splatter instead of spraying, giving you a poor finish. Or, the paint may not be able to exit the gun, clogging the nozzle and possibly damaging your paint set up. 

To improve atomization, avoid clogging your spray gun, and get better results, always thin latex paint before applying it with an HVLP sprayer. 

What to Use to Thin Latex Paint

Use water to thin latex paint. You can use any water to thin latex paint – bottled, filtered, distilled, or straight from the tap.

How to Thin Latex Paint for HVLP Sprayers

Follow these steps to appropriately thin latex paint for use in an HVLP sprayer. 

1. Decide how much paint you need. Adding water to latex paint can introduce bacteria. If the paint is stored, this bacteria has time to grow and can make your paint go bad. You should only mix the amount of paint you plan to use in one work session. 
2. Pour the paint into a clean container. A pitcher or bucket works well. It’s helpful to have a handle and some kind of spout since you’ll be transferring the paint to the sprayer once it’s been thinned. 
3. Dilute by 10%. Take the total volume of the paint in the clean container, and divide by ten to get the amount of water you should add to the paint. For a quart of paint, this is about six and a half tablespoons of water. If you’re thinning paint by the gallon, use one and a half cups of water for every gallon of paint. 
4. Stir for two minutes. Set a timer and use a paint stick to stir the latex paint consistently for two minutes. This allows the water to be thoroughly mixed into the entire container of paint. 
5. Test the viscosity. Dip a viscosity cup below the surface of the paint. Lift the cup, clearing the surface, and start the timer. Count how many seconds it takes before you see an interruption in the flow of the paint. 
6. Compare the viscosity. The best HVLP paint sprayers come with a recommendation about how thin liquids should be in order for the machine to function properly.  Compare your measured viscosity to the requirements of your paint sprayer. This is easiest if you use the same model viscosity cup mentioned in the paint sprayer documentation. If you used a different model of viscosity cup, you will need to convert your measurement in order to compare. 
7. Dilute by 5% (if necessary). If your latex paint is not yet thin enough to meet the requirements of your HVLP sprayer you will need to dilute it further. Take the original volume of paint and divide it by 20. This is the amount of water you need to add to dilute by 5%. For a quart of paint, this is around three tablespoons. For a gallon of paint, add three-quarters of a cup of water. 
8. Stir and check the viscosity again. Make sure to stir the paint for two full minutes to ensure the water is well mixed into the paint. The viscosity measurement should be lower after additional dilution. Continue diluting, stirring, and checking the viscosity until you arrive at the appropriate thickness for your machine. 

Once you’ve thinned your latex paint, you’re ready to start spraying.

Conclusion

Latex paint needs to be thinned before it can be applied with an HVLP sprayer, to avoid clogs and achieve smooth, even coverage. Water can be used to thin latex paint. Start with a 10% dilution, and move on to an additional 5% dilution if necessary. Stir the paint well between each dilution and check the thickness using a viscosity cup.