Air-dry clay is a very popular sculpting medium amongst hobby crafters. It is easy to use, cheap, and no kiln is required to harden it because it air dries. There are a couple of drawbacks to using air-dry clay, however. One of the biggest drawbacks is that air-dry clay tends to soften when it gets in contact with water or other liquids. This is also why one of the most often asked questions I get asked on a regular basis is if and how air-dry clay can be waterproofed. In this article, I will explain exactly how to waterproof air-dry clay and what method and sealants are best used for your project.
As a whole, air-dry clay can only be made waterproof by using liquid epoxy resin to seal it. It is possible to make air-dry clay water-resistant by using varnish, acrylic paints, or white glue to seal it. Waterproof clay can withstand constant contact with water while water-resistant clay can only survive little contact with water.
It is important to note that waterproof and water-resistance are two different things. Waterproof means that an object can survive constant contact with water, for example, be submerged in water or hold water, while water-resistant only means that the object can get wet without being damaged.
That being said, air-dry clay can be made waterproof and water-resistant but only to a certain extend.
What Can be Used to Make Air Dry Clay Waterproof
Air-dry clay hardens when the water that is present within the clay evaporates over time but when you reintroduce the clay with water then the air-dry clay will soften up again. So if you want to waterproof air-dry clay you have to keep water away from the actual clay at any cost.
As a whole, to waterproof air dry clay only liquid epoxy resin can be used because it is the only material that will create a protective coat that is strong enough to keep water away permanently. To make air-dry clay water-resistant white glue, acrylic paint, acrylic sealer, or varnish can be used.
Liquid Epoxy Resin
The only sure way to truly waterproof air-dry clay is to use liquid epoxy resin. It is a resin that consists of two compounds that have to be mixed before you apply them.
Once mixed the resin will start to set but don´t worry you have several hours before the resin is fully hardened.
Simply apply the resin as evenly as possible by pouring the liquid over your sculpture. Once the epoxy resin has hardened the air-dry clay will be waterproof.
I wouldn´t recommend using sculptures that have been sealed with epoxy resin as mugs or dishes or anything else that comes in contact with food.
There is special food-safe epoxy resin so if you want to seal your self-made dishes then I recommend using the food-safe resin instead.
But even when using epoxy resin to seal air-dry clay it won´t really be possible to use air-dry clay for pottery because the clay just isn´t durable enough and the epoxy seal will fail eventually.
You can read my article on using air-dry clay for pottery if you want to know more about that.
Acrylic Paint and Other Water-Based Paints
You can use acrylic paint, latex paint, and similar paints to seal air-dry clay. But sealing air-dry clay with water-based paints won´t make the clay waterproof.
It will only make the air-dry clay water-resistant, meaning the sculpture will survive direct contact with water drops, and it can survive water splashes but it will never be able to hold water, like a vase, and you can´t wash the sculpture with water.
So sealing air-dry clay with water-based paint such as acrylic paint, is really convenient but it will only protect your sculpture from small amounts of water.
To seal air-dry clay with acrylic paint simply apply the paint directly on the surface of the clay in multiple thin layers. Let the paint dry in between layers.
After about 2-3 layers the paint should cover the clay sufficiently. Simply let the paint dry and you are done!
White Crafts Glue
You can also use white crafts glue, such as mod podge or wood glue, to seal air-dry clay.
But that will also only make the clay water-resistant and not waterproof, similar to sealing air dry clay with acrylic paint.
Using white glue to seal air-dry clay has the added benefit of a transparent seal. So you don´t have to paint your air-dry clay and thus change its color instead you can apply white glue or similar types of glues that dry transparent.
To seal air-dry clay with crafts glue simply apply the glue in multiple thin layers to the surface of the clay and let the glue dry in between layers.
It should only take two layers until you covered the clay sufficiently. You can use a soft brush to apply the glue.
Make sure that you cover every part of the sculpture to ensure that it is sealed properly.
Acrylic Sealer or Spray Varnish
An acrylic sealer or spray-on varnish can also be used to seal air dry clay and make it water-resistant.
It works slightly better and offers better protection against water than white glue or acrylic paint but it will also only make the clay water-resistant and not waterproof.
I personally prefer using this method over using white glue or acrylic paints because it offers better protection, both sealers dry clear, and you can apply them pretty easily with a spray can.
But acrylic sealer tends to yellow when it is exposed to direct sunlight for long periods of time, so be aware of that before using it to seal your sculpture.
Acrylic sealer and spray-on varnish can be applied pretty easily. Just lightly dust the sculpture with the sealer and let the first layer dry for a few minutes.
Then apply a second and third layer in the same way. Once the sealer is dry your sculpture will be sealed.
Just make sure that you applied the sealer evenly to all parts of the sculpture.
Best Sealant for Air Dry Clay
Now that you know exactly what kind of materials and sealants can be used to seal air-dry clay the most pressing question you have on your mind is probably which of these sealants is best used for air-dry clay.
As a general rule, the best sealant for air-dry clay for sculptures that are only decorative is acrylic paint or white crafts glue. If the sculpture needs good protection against water then acrylic sealer or varnish should be used. Epoxy resin is only necessary for waterproofing clay.
In the end, the choice of sealant is entirely dependant on your project. If you want to know more about sealing and working with air-dry clay then consider reading my other article where I explain how to seal air-dry clay in great detail.