This page was last updated: May 23, 2010

Make sure your mold is clean before banding to pour. Open the mold to clear away any dust or debree with a soft brush. Place the mold flat side down and band with rubber mold bands or a mold strap with buckle. To test the mold for pouring, after banding with rubber bands, set the mold hole side up and place fingers in pouring hole. Try to pull the mold apart with normal pressure. If the mold separates easily, the mold needs more bands or tighter bands. A mold requiring one half gallon or more of slip to fill should be banded with a mold strap.

When the mold is banded properly, fill the mold to the top with liquid clay slip. Do this while moving the slip in a circular or back and forth motion. This will help to prevent hard spots from forming which is where the slip hits the mold at the same spot and starts to set up first. Hard spots have a tendency to keep glaze from applying properly.

Be sure to have enough slip to fill the mold before beginning to cast the greenware.  If not, you will create lines that will form around the casting.  Fill the mold, including the spare.  Keep the mold filled.  Check from time to time (set a timer if necessary to remind you to check the mold). The size of the mold, the humidity in the air and the dryness of the mold will determine the length of time needed for your cast to reach approximately 1/8"- 1/4" thick.

BASIC MOLD POURING

Preparing Your Mold To Pour

Once the casting reaches the thickness you desire, pour the excess slip out slowly. If the mold has a small pour hole and a gurgle sounds when dumping the mold, pour it slower so the casting does not pull away from the wall of the mold and collapse.  When the mold is completely drained place it up side down (pour hole down) until it completely stops dripping. Turn mold hole side up and let to dry. When the casting has dried to a damp feel (no longer wet), trim the spare (excess clay) from the pouring hole being careful not to disturb the casting. Unless the top of the casting has a great deal of detail and shape, you can gently loosen the spare from the sides of the mold with the LUCY KNIFE.  Then, gently pull the spare in towards the center and up, and it will usually break at the end of the spare. You can now take the lucy tool and cut the jagged edges of the spare for a clean casting.

Opening mold and removing ware

After the casting has had a chance to dry some, remove the bands or strap. Now place your thumbs in the pouring hole and gently separate the mold. When the mold has been separated a little, lift the top half of the mold straight up, and quickly turn the lifted piece over. The inside of the mold is now facing up. Sometimes the casting will remain in the mold half that is lifted. That's why we turn it over quickly. Grab the half of the mold that has the casting. Hold it in one hand and gently hit the mold on the sides using your other hand or rubber mallet until the casting releases from the mold. Once the casting releases, place the mold and casting on table. Using both hands gently grasp the casting and place on clean surface. At this stage your casting is leather ware and is very soft. Be careful not to distort it. Let it set until it is bone dry. The dried piece is greenware.

A mold is the reverse image of the greenware that you cast from it.  Molds in the ceramic industry are made of plaster.  The plaster is mixed with water at the correct ratio to form a durable and porous mold.  The plaster mold absorbs water from the slip, which allows you to create high quality greenware.

Parts of a mold

Mold cavity - negative image of casting (inside)

Spare - pour gate or trim area

Seams - area where the parts of the mold join together

Face - outside surface of the mold

Keys or locks - male and female notches that match together when closing

Types of Molds

One part mold - also known as an open-face mold or dump mold, usually flat pieces like wind chimes, etc

Two part mold - most common mold that has two parts that need to be strapped together before casting

Multi part mold - a mold with 3 or more parts also requiring strapping together. Items in this category are large Christmas trees and pieces with footed bottoms

Gang mold - 2 or more part mold which allows you to cast multiples of a similar item in one pouring

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Bev's Ceramics. Inc.