Pottery and Ceramics
Making a Simple One Piece Plaster Mold
Plaster molds are used in ceramics to pour multiples of a single object with liquid clay called slip.
Making a mold can be a fearful task for some people, depending on how complicated it is.
Mold making is a highly skilled and highly paid job, within large ceramics companies like Rosenthal or Royal Doulton.
On the other hand, anyone can learn the basics of simple plaster mold making.
Tools for Pottery
Tips & Techniques for Pottery and Ceramics
Clay Pottery Craft Projects
Clay Pottery Articles of Interest
Old Time Pottery History
Pottery and Ceramics
Featured Potters Gallery
Pottery and Ceramics Definitions
All About The Clay
All About Pottery Glazes
Materials required:
A bag of high quality modeling plaster.
Some low quality, recycled clay that will be discarded later.
4 wooden boards, 8 x 12 inches or roughly three times the width of your bowl shape.
Eight nails.
A thrown and turned, leather hard, solid tea bowl shape without handles or other undercuts.
A bucket.
Some water.
The first step in making your mold is to put together a box for the plaster.
We will make this by nailing the four boards together to make a bottomless box.
The edges should not be flush, but actually sticking out.
Make sure you don't nail them together too well, as you will be taking them apart later.
Once the boards are nailed together, place them on a smooth surface, like a table top, and wedge clay sausages into all corners.
Make sure none are left out, as this will stop any plaster seepage.
Now place your bowl shape flat side down into the center of the box.
Push it down a little so that it sticks, moisten if necessary.
Mark the height of the foot of the bowl with a marker pen on one of the inside boards. Mark a second line at about 50% higher.
Now you are ready to mix the plaster.
Follow the instructions for plaster mixing on the bag.
Make sure you don't breath in any plaster dust, as this can be health hazardous, use a mask.
Thoroughly mix the plaster in the bucket with your hands to get rid of any lumps.
It would be safer to use rubber gloves for this, as the plaster is alkaline and has other chemicals added also and may irritate the skin.
It should take you less than 10 to15 minutes for this, because the plaster will start to set up.
Pour the plaster over the cup shape, right up to the second mark.
Excess plaster can be left in the bucket to harden.
This can be knocked out later.
Let the plaster harden for at least a couple of hours, better overnight.
Then, using a hammer, carefully knock the boards apart.
You now have a plaster mold with a positive form sticking inside.
The clay bowl form will shrink on drying and then easily pop out and voila! you have a plaster mold for making multiple tea bowls, either by slip casting or press molding.
Press molding is done by pressing soft clay into a one piece mold, trying to make it the same thickness all over.
Growing old is inevitable...growing up is optional! |
