In a bowl, mix a ratio of 80% PVA glue to 20% water to create a creamy consistency, and then coat your fully dried clay piece, and allow the sealer mixture to dry. Once you have applied your PVA glue mixture or acrylic medium, you can then apply 3 coats of acrylic paint to seal your work.
The best option to provide a water-resistant, durable seal on air dry clay objects is to use a polyurethane or acrylic sealer. These provide a durable, water-resistant finish to protect the air dry clay and prevent it from yellowing.
If you want to make your clay water-resistant I always recommend using either a clear polyurethane varnish or an acrylic sealer. Both of these create a non-porous transparent layer that seals your clay project. They can be brushed or sprayed on and usually come in either a matt, satin or gloss finish.
You don't have to seal polymer clay. Baked polymer clay is durable plastic and therefore more durable than any sealer. Sealers and varnishes will not prevent breakage. If your projects are brittle, address your baking process.
Epoxy resin is another way to make polymer clay pieces shine, if you are a resin crafter and are familiar with how to use it. If you don't have a resin kit to hand, it can be easier to stick with regular varnish. You can also use PVA glue to varnish polymer clay, which I will discuss below.
Some of the most popular ways to add a glossy or shine to your clay jewelry is with a glaze or sealer of some sort. We already mentioned liquid clays as a good option. Another great option is an acrylic sealer like polycrylic . This is a water-based protective finish gloss.
Sealing Your Finished Pieces.
As air dry clay breaks down in water it's not possible to truly waterproof it. However, you can help make it water-resistant by applying a coat of acrylic paint or varnish. The most popular options are Modpodge (I like the Dishwasher Safe Mod Podge) and the DecoArt Triple Thick Glaze.
Many Stoneware, Porcelain, and Ball clays can all vitrify when fired at high temperatures – typically over Cone 10, which is 2345℉ (1285℃). So, if you are using one of these Types of Clay and firing to a high enough temperature, you don't need to worry about glazing your pottery.
Most air dry clays are sticky, and you don't want that on your work surface. We recommend protecting the work area with items such as wax paper, silicone baking mats, or vinyl placemats.
OPTION 1: A great DIY/ Homemade sealer option is mixing PVA glue and water. In a bowl, mix a ratio of 80% PVA glue to 20% water to create a creamy consistency, and then coat your fully dried clay piece, and allow the sealer mixture to dry.
White craft glues are great for sealing clay, because they are nontoxic and easy to use, and you can get them very easily in any crafts store. So they are the cheapest and easiest way to seal your clay. Simply apply a thin layer with a brush to your sculpture and let the glue dry for 5 to 6 hours.
Vaseline (petroleum jelly) is a much better option to soften hard polymer clay! Put a small amount of Vaseline on your fingertips and rub it into a small ball of clay. Cut the clay into smaller pieces and then squash the pieces together. Add more Vaseline, flatten the clay by rolling it out, then knead it again.
Petroleum Jelly
The second polymer clay tip, vaseline does miracles to clay.
In short, the best paints for air-dry clay are water-based paints like acrylic paints or tempera. Water-based paint has to be sealed after they have dried, however. Enamels, latex, or spray paints can also be used and they don´t have to be sealed afterward.
Some products, such as Terra Cotta pottery, are left unglazed so they can remain porous and absorb water over time. However, this is not a desirable trait in an item intended for contact with food. Food-safe unglazed pottery falls into the category of Stoneware, Porcelain, and Ball clays.
Glazes consist of silica, fluxes and aluminum oxide. Silica is the structural material for the glaze and if you heat it high enough it can turn to glass. Its melting temperature is too high for ceramic kilns, so silica is combined with fluxes, substances that prevent oxidation, to lower the melting point.
If the clay pieces begin to dry out, place them in a resealable bag and spray them with some water. Seal the bag and wait a few hours. The clay should be ready to use. If you have larger pieces that have completely dried, or old unpainted projects you want to reuse, you can still revive the clay.
If your pottery is half an inch thick or greater, then it is recommended to leave it to dry for up to three weeks. If you live in a humid climate and want to ensure that the clay is fully dried, then it is worth leaving pottery for an additional week to ensure it is completely dry.
Can I use PVA glue as a varnish? PVA glue isn't great for acrylic or oil-based works but you can use it on air dry clay. To use glue as a varnish on air hardening clay, just mix a ratio of 1:1 PVA glue to water.
Clay must be fired in a kiln to harden, while modeling clay will harden. This means that clay sculptures are more permanent than modeling clay.
The Bisqueware Stage
The bisque stage permanently changes the form of the clay and so you can not go back after this stage. The process involves firing the clay to remove any chemically bonded water in the clay. The bisqueware stage is the ideal stage for glazing.