Casting from a Plaster Mold

Part 2 on Casting a 3 Part Mold

 

After the mold is cleaned and left to dry for a few days to a week, it is time to make your first cast.

You can purchase straps to hold your mold together, or in this case, inner tube rubber, cut into strips.

mold cleaned up and ready to cast

This mold is held together by inner tube rubber, cut into pieces

 

Filled with clay slip

Pour the liquid slip carefully into the mold up to the top.

 

You should put on a timer for about 15 minutes at first, keeping a look out for the level of the slip. As the water is absorbed into the plaster, the level of slip will go down.

Mold absorbing water

Top up the slip as the moisture is absorbed

 

You will want to experiment on the timing, but for this casting, 30 minutes is about right to cast a piece. However, this could change depending on how many pieces you cast and how damp the mold gets as well as how thick/thin your slip is.

When you feel that the casting is thick enough, pour half of the slip back into the container and then swirl the remainder of the slip around the casting for a few minutes before pouring it out.

Place the mold onto an elevated prop to allow the remainder of the slip to drip out.

The mold will now take an additional time to dry enough to remove the piece from the mold. In this case it is 30 minutes of drying time.

 

Spout cleaned

Clean the spout hole, being careful to not let the trimmed pieces fall into the sculpture.

 

When dry and ready to remove the piece, clean the spout hole. Take the bindings off from the cast and carefully pull the two pieces apart.

 

mold opened up

One side of the cast has been removed, if the piece is dry enough, carefully pull the sculpture out from the second part of the mold.

 

In this sculpture, the third piece can now be removed as well.

As the pour spout is located at the bottom of the sculpture, we now have to close that opening.

Pour a bit of liquid slip onto a flat plaster bat and place the sculpture on top. This will quickly adhere to the sculpture and create a smooth bottom.

Trimming and cleaning up cast

Here you can see the cast sitting on plaster on top of some liquid slip to fill in the spout hole in the bottom. The opening at the top is also being trimmed.

 

Your sculpture will have seams that can now be cleaned up and you can cut out the opening to the vase, again being careful not to allow the piece to fall into the sculpture.

Bisque fired hand vases

ten castings coming out of the bisque kiln.

 

And there you have it, the end result, bisque fired and ready to glaze.