One of the really nifty things that some potters do is to make a plaster cast of their work. This way it’s easy to replicate perfectly every time. If you are reproducing lots of the same things, like coffee/tea mugs, you are most likely going to do it via slip casting. This is a process where you pour slip (liquid clay) into a plaster mold and let it sit for however long and then pour out the extra slip and then let the coating of slip that’s accumulated on the inside dry for however long.
Me… well, I don’t have a large scale operation. But I did have a request for a 10″ sphere. You might as well grab a cuppa and have a sit with me as I tell you the story of the spheres. That’s right, spheres…as in plural.
I enjoy a challenge. Really, I mean, who doesn’t? It makes you bring your “A” game and figure out how to do things in a different or better way than before. Now, I haven’t ever made a sphere this big. It has to start off as a 12″ sphere so that after both firings it will be about 10″ (the clay that I will be using for the sphere shrinks about 13% when it’s done with both firings).
I figured that it would be best to build the sphere around a mold of some kind. My first attempt was done on a 12″ hemisphere. I got one done, and at the proper stage, I pulled it off and made the next one. These were brilliant until I tried to join them. One was much to wet, the other much to dry. Back to the recycle bin they go.
The second attempt was made onto an inflatable ball. It went brilliantly and looked spot on until I couldn’t get the ball out of the inside – I had forgotten to use a “release agent” of some kind (in this case newspaper) and the clay stuck to the ball. Back to the recycle bin.
The third go was on the inflatable ball, lined with paper. This one was brillant, spot on, and I got the ball out! I went to clean it up on the wheel and, well, I didn’t have it secured properly, so it smashed into a billion bits. They are still out there. Paper and all. This one didn’t go to the recycle bin.
I wasn’t giving up… I knew I could do this!
On the fourth go I decided to build the sphere around two 12″ hemispheres (put together). This was the best one yet, it looked amazing and I was ecstatic. Unfortunately, it appears that if you fire styrofoam, it is toxic and will destroy, or severely mess up your kiln. So that clay went to the, you guessed it, recycle bin.
For try No.5, I decided to attempt to make a plaster cast of the 12″ sphere. This one took prep work. I located a vessel (big cardboard box) that could hold the sphere and allow enough space all around for the plaster. I lined it with plastic bags (so the cardboard box would survive 2 castings) and made the stopper for the ball. I threw in a couple of pounds of clay inside the sphere so it would be weighted down. I have neglected to say that I was planning on using the styrofoam hemispheres, only put together, for the casting. It was a beautiful Saturday, my studio assistant (that means my oldest son, Spencer) and I set out on a quest to make the biggest casting I’d ever make.
Oh my! What a mess… I won’t bore you with all the details, just know that it worked and after 8 hours of mixing, pouring, cussing, complaining, more pouring and praying to the plaster gods, it was complete. Now to let it dry….
So, meanwhile, attempt number 6 was made by doing the same as attempt number 3. Only this time, I didn’t let enough air out of the ball when the clay was drying, so it had major cracks that couldn’t be fixed. Yuppers, in the recycle bin it went.
Attempt number 7 was made by using the kinda dry plaster cast. We were going to slip cast the sphere. It took the hubby and one of the cousins to help and get all the clay into the cast. I left the slip a bit thicker than usual because I thought (well, there’s your problem) that it would be better since the mold is so big. We let it sit 8 hours and then poured it out. Well, attempted to pour it out. What a nightmare. I didn’t account for the “suction” of the mold – being as big as it is. It took an hour to get most of the clay out of it. Seriously, I have buckets of clay covering the floor of the studio. Thankfully, we were outside (in the outside studio) and its easer to clean, but, Yuck! we let it sit overnight to dry and un-molded it in the morning. Pulling the 50+ pound top off was bad enough, but when the clay fell out of the top of the mold onto the massive amounts of clay in the bottom of the mold, I knew it was pointless. The good news, this clay stayed in the mold to be recycled.
So, onto attempt No.8. This time, I made segments out of the clay and put them together. This one worked and it fired up too. It just didn’t make it out of the kiln like it went in. It cracked, it chipped and it was a mess.
I wasn’t going to admit defeat, so I gave it one last shot. Since the segments worked better than any other method, I tried it again. I made sure that all the slabs were the same thickness (thank you pastry roller bands) and reassembled. This time, it worked, it’s a bit rough, but it worked. It fired up well and I have gotten it painted. It needs to be fired again, but I am very hopeful about the results.
It looks amazing and I have learned so much from this experience. The time frame of all of this, it’s been about 3 months that I’ve been working on this. I am just so incrediblely grateful that my client has the patience of a saint. I’ll post photos when it’s all done so you can see. If you’re dying to see it now, you can check out some of the progress on instagram or twitter – @whimsikettle.
Featured image courtsey of: https://pixabay.com