The sealant gives the finished air-dry clay piece a nice sheen and will make them more resistant to the elements, but they still will not be water proof. Sealant is essentially liquid glue so pieces made with air-dry clay and then sealed cannot be used with water or food.
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.
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.
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.
Sealing Your Clay Painting
Once you are done painting the clay, you need to seal it to protect it and make it waterproof. If you do not seal the paint, it will eventually begin to peel off, or if you get water onto it, the paint can be washed off.
Sealing air-dry clay before painting is not necessary. It will actually make it harder to paint the clay after sealing it. So Paint the clay with water-based color first and then seal it with acrylic sealer or varnish to protect the colors from water, sun, or scratches.
Varnish is a non-pourous, transparent layer that is put on top of a final artwork (be it painting, drawing, sculpture, you get the idea). Varnishes can be removable or permanent. They can be brushed or sprayed on and generally come in 3 different levels of sheen.
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.
While not everyone has access to a proper pottery kiln, one of these methods for glazing pottery without a kiln is called Raku Firing. This method requires a bisque fire to turn the clay into a ceramic material. The temperature needed depends strictly on what type of clay is being used.
You can incorporate some PVA glue directly into the small chunk of clay and knead it. Or mix the glue with water and use this mixture instead of clear water while sculpting. This trick makes the clay very firm and durable. It'll be harder to sand, but it works great for most areas.
After your creations are completely dry, it's time to seal them! Clay is porous, the air dry clay will become pliable again if exposed to water or moisture. Sealing the clay will prevent this from occurring.
As mentioned, acrylic and tempera paints are the recommended choices of paint you want to be using on air-dry clay. Acrylic is the best paint for clay in general as well.
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.
Once your air-dry clay project is completely dry, you can apply one layer or more of clear nail polish as a sealant. Keep in mind that these layers do not make your project completely waterproof but instead water-resistant.
Since terracotta (clay) pots are a porous material, it is essential to seal them. Sealing them protects your plant's roots from quickly drying out. It also protects any decorating, such as paint and decoupage.
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.
Water can be added to Air-Dry Clay to soften or join pieces. If too much water is added and clay is very soft, allow excess to evaporate before molding pieces; otherwise, cracking may result.
No, but you can make it water-resistant using a glaze, waterproof sealant or varnish. This doesn't mean you can leave your clay to soak in a bowl of water but it does mean you can wipe it clean with a damp cloth.
Cracking is normal in air dry clays: it's caused by shrinkage because of the loss of the water inside the clay body. Cracking in air dry clay is typically caused by sculpting over an armature or using a lot of water, either to mix the clay or to help it adhere onto a previous layer.
Clay has a memory. So in an effort to erase the memory of a crack, score the area in question deeper and larger than the crack itself (2), then place a bit of scored soft clay into the space you've made and compress it with a rib (3, 4). This will heal a crack in most cases, depending on how dry the cracked clay is.
Clear acrylic, water-based polyurethane varnish or modge podge are the best options for sealing paint to ceramic surfaces.
Once cured, polymer clay is waterproof and doesn't need to be sealed against moisture. This is because it's oil-based, rather than water-based like air-dry clays are – which makes polymer clay an ideal component in projects like snow globe making!