Is Chalk Paint Waterproof? (& How To Make it?)

Chalk paint has some impressive qualities; it dries fast, it’s easy to apply, and the finish is colorful. But is chalk paint waterproof?

Chalk paint isn’t waterproof, but it’s water-resistant. This means the paint can withstand exposure to water for a limited time. But, if exposed to constant water, the paint will get washed off. Because of its weak water resistance, you shouldn’t use it for outdoor surfaces.

To make chalk paint waterproof, you must apply a waterproof sealer, such as spar varnish, over its finish. The sealant will produce a glossy clear coat that repels water and protects the paint. 

Chalk Paint Water-Resistant Levels

Chalk paint has a low level of water resistance. If exposed to constant water, the paint will get washed off quickly because it doesn’t have additives or resins that make its coating waterproof. 

Also, chalk paint is water-based and has a dry textured finish. All water-based paints use water as their paint solvent, meaning the resins of the paints are dissolved in water. So, if you add water over t a water-based finish, the resins will dissolve and the finish will get removed.

Since chalk paint doesn’t have a glossy slick finish that repels water, the water will accumulate (stay) inside the textured finish and won’t slide off. This allows the water to penetrate the coating and dissolve it. 

However, this doesn’t mean you can’t wash chalk paint coating with water. Chalk paint has low levels of water resistance, meaning it can withstand water for a short period of time. So, you can clean it and remove the water without damaging the finish. 

How To Make Chalk Paint Waterproof?

To make chalk paint waterproof, seal it with a waterproof sealant. The waterproof sealant will produce a clear coat over the paint that protects it from water, moisture, and other damage.

You can use spar varnish, exterior polyurethane, wax, or lacquer to seal it.

Here are the tools you need:

1. Fine-grit sandpaper
2. A paintbrush
3. A waterproof sealant
4. Clean rags

1. Clean and Scuff The Chalk Paint

First, clean the chalk paint with a dampened rag. Cleaning will remove dust and filth from the finish. If you don’t clean, the dirt and dust will show after the sealant dries. 

Once the finish is clean, sand it with fine-grit sandpaper (220-grit). Sanding will scuff the coating and create tiny ridges that the sealant can stick into. This improves the adhesion between the paint and the sealant. However, sanding it is optional. If you sand it, re-clean the finish to remove dust.

2. Apply The Waterproof Sealant

Once the finish is dry, clean, and sanded, apply a waterproof sealant. The sealant you use must be waterproof, compatible with chalk paint, and designed for exterior use. Spar varnish or exterior polyurethane are a great choice. 

Waterproof sealants are reinforced with additives that make the coating durable enough to withstand water exposure. The finish of the sealant will protect the paint (and the surface underneath) from weather elements. 

To make chalk paint waterproof:

1. Prep the sealant (thin, mix, or shake it) based on the manufacturer’s instructions.
2. Apply 3 coats of sealant using a paintbrush or sprayer. 
3. Wait until one coat dries before applying the next one.
4. Optionally, you can sand between coats of sealant. 
5.  Allow the last coat of sealant to dry fully (cure) before using the surface. 

3. Test Its Waterproof Qualities

Before the chalk paint becomes waterproof, the sealant you applied must dry fully (cure), this can take a few days. So, don’t expose the coating to water or rainfall before the sealant dries. 

To know if the paint is waterproof or not, use the water test:

1. Pour a small amount of water over the paint (and sealant) coating.
2. Wait a few minutes.
3. If the water soaks into the coating or takes the paint color, the finish isn’t waterproof. 
4. If the water has a clear color and doesn’t penetrate the finish (stay over it), the finish is waterproof. 

Using Chalk Paint Outdoors

You shouldn’t use unsealed chalk paint outdoors because the paint isn’t waterproof and will get washed off if exposed to rain. Chalk paint doesn’t have extra additives that make the finish durable enough to withstand exposure to water.

If applied outdoors, unsealed chalk paint won’t last more than 1 month (depending on how often it rains). Dust and wind can also damage the finish. So, an unsealed finish will peel off quickly on outdoor surfaces. 

To use chalk paint outdoors, seal it with a waterproof wax, polyurethane, or spar varnish. The sealant will produce a waterproof coating over the finish and protect it from weather elements. 

Sealed chalk paint will last 3-5 years outdoors before starting to peel off. If you touch up the sealant (once in two years), the finish will last even longer. 

Rain

Rain does affect chalk paint. Heavy and constant rainfall will wash off the finish. However, rain affects paint on a horizontal (or flat) surface more than on vertical surfaces. 

On a vertical surface (wall), the rain will drip off the finish and won’t damage it as much. On average, unsealed chalk paint will last 6 months on vertical surfaces.

However, on flat or horizontal surfaces the paint will get washed off quickly by rain. That’s because rain will fall and stay over the finish since the surface is flat. On average, chalk paint on outdoor horizontal surfaces won’t last more than 1 month. 

To make chalk paint thrive under rain conditions, seal it with a waterproof sealant. However, the sealant must dry fully (cure) before the finish becomes waterproof. So, if the sealant is still wet (not dry), and exposed to rain, the sealant and paint will get washed off. 

Related Read: Is Chalk Paint Durable?

Final Words

Chalk paint isn’t waterproof and has low water resistance qualities. If exposed to constant water, the paint will get washed off. To make it waterproof, apply a sealant over it. The sealant will protect it from moisture, water, scratches, and other damage.