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How to Thin Latex Paint for Airless Paint Sprayer?


Latex paint is one of the most commonly used paints for home interiors and exteriors thanks to its low odor, easy cleanup, and durable finish. The latex paint can be turned into a spray of ultra-fine droplets by airless sprayer. In some cases you need to thin the latex paint, so take a moment to consult this help to learn more.


Why Thin Latex Paint?


Latex paint is already fine in consistency straight from the can. So why would you need to thin it further for an airless sprayer?

Because older paint may lose water content due to evaporation and become thick or clumpy;

Need to spray a very fine mist coat, such as on siding or trim. Thinned paint creates a smoother finish;

Painting in very hot conditions. The heat can thicken up latex paints;

Or you want the paint to flow and level out better on the surface after spraying.


How to Check If Paint Needs Thinning


Before you thin latex paint in the sprayer, first do a quick viscosity test to see if it even needs thinning. Dip a paint stick into the paint and then lift it out. Observe how quickly the paint drips off the stick. If it runs off in a slow, thick stream, then thinning is needed. If it drips off in a steady, uniform flow, the paint may be at the right consistency already.


You can also observe the consistency of the paint by running it through a small test section on cardboard. If the spray fans out evenly, the paint likely doesn't need thinning. If it sputters or leaves thick globs, it needs water to thin it.


Using Water to Thin Latex Paint


The best way to thin water-based latex paint is by adding water. Water is compatible with the latex polymers, so it blends seamlessly into the paint. Use clean tap water at room temperature to thin latex paint. Do not use hot or extremely cold water, as this can shock the paint. 

Distilled water is ideal if your tap water is hard or has contaminants. Never use solvents like paint thinner to thin latex paint, as it will curdle and ruin the paint.


How Much to Thin Latex Paint?


Only thin latex paint as much as needed for proper spraying. Over-thinning the paint will cause sagging and dripping. For airless sprayers, latex paint only needs to be thinned by about 10-15%, or 1/8-1/4 cups of water per gallon of paint.


Test the consistency by spraying a small area to see if the thinned paint sprays evenly without sputtering or spider webbing. If needed, thin in additional water in small increments, remixing thoroughly before testing again. But take care not to over thin, which can cause the paint to drip and run, reducing hiding power.


How to Thin the Paint Properly?


1. Stir the paint thoroughly before adding water, this ensures even thinning.


2. Pour the needed amount of paint into a separate clean bucket. Use a paint strainer to remove any lumps or particles that could clog the sprayer.


3. Add water in small increments as noted above, mixing completely between each addition. Use a stick to scrape the bucket sides and bottom while mixing.


4. Use an up-down motion rather than circular stirring to avoid creating bubbles in the paint.


5. Allow the thinned paint to sit for 10-15 minutes so the water fully incorporates.


6. Do a viscosity test using a stick. Properly thinned paint should drip steadily off the stick.


7. Test spray on cardboard to check the spray pattern before spraying the surface.


Tips for Thinning Latex Paint


Only thin paint that will be used the same day, as it can spoil if left to sit thinned for long.

Thin paint in a separate container rather than thinning the entire can, in case you over-thin it.

Use a quality latex paint designed for airless spraying. Budget or bargain paints may be too thick.



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