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Hi, We have been doing the jigger for the first time and the pieces whatever we are making have a cracks in a same pattern in a same location, and we are using Terracotta clay to make the pieces and here I m attaching the cross sectional pieces of the molds., and in the molds I have few doubts and I would like to get clarified so that I can reduce the cracking doors one by one., Does the thick and thin portions of the molds absorbs water differently so that the pieces are cracking ? As you can see the picture of the pieces the cracks are happening in the place where the side wall is connecting with the curved edges, and the cracks are happening only with our terracotta clay and we have tried quite a lot of receipes to avoid cracks but nothing is helping out and the cracks are happening in the inside of the pieces and the outside wall is just fine. Also we have tried jiggering few pieces with our stoneware clay and we havent have any cracks in the stoneware. Does the uneven wall thickness is the reason to get the cracks ? Wi only the Terracotta is cracking and not the stoneware ? Wi the inner wall is cracking and it didnt extend to the outer wall ? Does it anything to do with the plasticity and the composition of the clay? As far as the design is concerned, we make sure theres no undercuts in the design and even the wall is not striaght and it has an angle of 10% for easy releasing., we used to have few issues with our clay body which I was working with Tom (Glazenerd) to solve the issue, but apart from that I would like to know what are the other possible reasons for the cracking.
Has anyone tried any products from Gladstone Engineering? We're in the US and don't really have any exposure. We're considering their jigger & jolly machine. They also have a spray booths, automated slab rollers, a "super pug", and something I've never seen...get ready...a "foot wiper machine". Seems kind of silly but it looks like the Brits are having a lot of fun!!! Any info would be greatly appreciated. Ernie
We are jiggering plates (see attached) with an Axner Power Arm onto pure and simple hump molds. We are experiencing a tremendous amount of cracking and need help! We have done a very similar form without the jigger arm, by slabbing and attaching the foot and had no cracks at all. We used a different clay body with grog but should have worked the same as 181 (has grog). None of our other forms are experiencing cracking in the dry room, regardless of the clay body however none of the other forms are jiggered which leads us to believe it is related to jiggering. First guess is perhaps the pressure of the jigger arm is causing the clay to stick to the plaster. When the clay dries too quickly it has no where to shrink and cracks internally on the plaster, then externally on the ware boards. We don't know any way to remedy this other than just not jiggering.... Troubleshooting thus far: - Drying too quickly: Initially we thought it was only due to the forms drying too quickly and the humidity. So we brought in a humidifier into the dry room. Cracks still happening. - Clay Body (grog vs no grog): We were previously using Standard 365 (no grog). We switched to Standard 181 and...still the same amount of cracking. These are all just guesses as we are still experienced cracks galore...we'd certainly appreciate any thoughts!! Best, Ernie email@example.com