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These molds were my first effort using 3D design and 3D printing. They served well for making hundreds of pieces. They were part of a 2019 casting-jiggering project to reproduce a Medalta Potteries 1966 mug. Even with a thick handle like this and slip made using kaolin and ball clay not intended for casting, the molds split in less than an hour when casting solid (and in half an hour when casting hollow). As a parting agent on the 3D-printed surface I used Murphy's Oil Soap. The sidewalls had a draft of about 5 degrees and the handle cross-section was round rather than oval, so the plaster molds released without corner breaking.
This mold had spares - they did not provide a big enough reservoir and I later switched to using 3D printed spouts. These also had plaster matches (I later found that no matches worked better on this size and shape of mold). I went through multiple more versions perfecting the process to enable making handles of more difficult shapes and finally using 3D printed natches.
This is a product of a casting-jiggering project I did in 2019 to recreate a 1960s Medalta Potteries mug. The first step was drawing a profile in 2D (using Adobe Illustrator) and then working with a Fusion 360 freelancer at Upwork.com to create a quality 3D drawing. 3D printing this mock-up was possible after that, using my favorite 3D slicer, Simplify 3D. The mug was drawn "parametrically", that is, measurements and geometric relationships were built-in such that changing contours and the size preserved the original design. The first production mug, made about a year later, is on the right. Molds were scaled up 10% from this mockup size so that final pieces would be this size, however the firing shrinkage of the clay turned out to be about 12%.
Projects |
Mug Handle Casting
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Projects |
2019 Jiggering-Casting Project of Medalta 66 Mug
My project to reproduce a mug made by Medalta Potteries more than 50 years ago. I cast the body and handle, jigger the rim and then attach the handle. 3D printing made this all possible. |
Glossary |
Slip Casting
A method of forming ceramics. A deflocculated (low water content) slurry is poured into absorbent plaster molds. As it sits in the mold, usually 10+ minutes, a layer builds against the mold walls. When thick enough the mold is drained. |
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