Slip casting is the common method used to make latex masks from liquid latex rubber. The latex rubber is poured into the mold, allowed to sit for some time before being poured out again into the container. The liquid latex that adheres to the mold is allowed to cure properly before being demolded to form a thin skin mask.
However, not many people may be aware that the same technique can be used to make hollow ceramic and porcelain casts.
Following are some simple instructions on how it’s done:
Plaster molds are usually used for this purpose as the porous plaster will effectively suck the water out of the clay slip. Clay slip is formulated by mixing dry clay powder with sodium silicate (water glass) and water to get the desired consistency. You can make your own or purchase commercially sold clay slip from the market. It is available in different consistencies and the consistency will dictate the time taken for casting.
Clean and dry both the halves of the two-part plaster mold before matching them up and seal properly. Further secure the mold with rubber bands so that there will be no leaks later.
Now slowly pour the clay slip into the mold. Fill it till the top and wait for it to settle. Slowly a layer of ceramic will start building along the walls of the mold. The thickness of the layer will depend on the amount of time you wait. Generally, waiting for 15-20 minutes should render a cast of 0.5 cms. thickness.
You will find that the level of clay slip in the mold lowers gradually while you wait as the plaster mold sucks the water from the clay. This is what causes the clay to thicken along the edges and gradually form a cast. You can keep refilling the mold to maintain the desired level.
Once the desired thickness is achieved, it’s time to pour out the excess clay slip left in the center of the mold. Gently tilt the mold to one side and allow all the excess material to drain out. Do not flip the mold completely in a hurry. Then place the mold face down to ensure every last drop comes out.
Place the mold on its side and let it cure completely on the inside. Once cured, all you have to do is separate the mold halves and gently remove the cast from the mold before finishing it off properly. A lovely hollow ceramic cast is ready! It can be fired in a dry kiln to further harden it permanently.
It is simple and easy to reproduce a ceramic copy of almost any object in this manner. In fact, slip casting techniques are commonly used for making multiple copies of plates, bowls, vases, statuettes and other decorative ceramic objects. They can be glazed, decorated or painted before being sold commercially in the market.