Ceramics at home: Slip casting mugs

Having had brief exposure to the concept of slip casting in MSE classes years ago, I decided to make some mugs as Christmas gifts using a mold I'd acquired years back. The process was fairly straightforward as I chose probably the laziest and most repeatable approach to forming ceramic objects. The first step was acquiring the slip, glazes, rubber bands, and a sturdy bucket. All together this totaled about $20 between Marjon Ceramics and Ace hardware. I went with low-fire slip on their advice, specifically because ceramic slip suffers substantially more shrinkage on firing (about 1/3 shrinkage compared to 1/15 for low-fire slip).

The mold was banded together after a few minutes or sorting out the best way to do that (the single vertical band required rotating the mold pieces and bracing them with books on both sides while I lowered the band on a bit at a time). The slip was well agitated then poured and allowed to deposit for about 30-35 minutes, which turned out to be a little less time than I should have allowed. The excess was poured into the bucket and allowed to drain at an angle for several minutes. This was then transferred back to into the jug using a funnel. A knife was used to trim off the sprue (excess lip).

It took about two hours for the deposited clay to release from the mold. At that point the mold was carefully removed from the clay, being very careful not to dent nor gouge the soft clay.

The mug was left in front of a small floor fan over night to drive off the excess water. The next morning, using a wet paper towel, the flash, seams, and rim were smoothed out. Once I had all four of them complete and dried, I packed them up very carefully and made the trip back to Marjon to get them fired. They were able to get them done quickly, taking about two days to bisque fire.

After the bisque fire they took on a flat off-white color and much smoother texture. I applied two coats of glaze to every surface, choosing different colors for the different mugs. While the outside surfaces were brushed on, the interior surfaces were rolled on; that is, the glaze was poured in and the vessel rotated to produce a good coating of all the surfaces.

Once glazed there were handed back over to Marjon for the final firing cycle. Two days later I stopped by and picked up the mugs, just in time for the Christmas party too.

The resulting mugs were a bit thin, so if I try this again (and I probably will, given how much leftover slip I have) I'd likely increase the slip time from 30-35 minutes to 45-55 minutes to produce heftier mugs and spend more time cleaning up the seams, which ended up being really apparent in the finished pieces due to variations in glaze thickness. Also I would consider more detailed glazing methods or use of ceramic decals to put designs on them. As a first foray into making ceramics at home, I'd call it a success.