HaleyChoice Posted February 20, 2022 Report Share Posted February 20, 2022 I bit off more than I could chew. You can watch the attached video, which explains my process and what led up to the disaster. I recently acquired a three-piece mold for my Wall Peen design. Here in the photos, you can see that it is hollow. Slip casting the form has been going okay; it took a few tries to figure out the timing for how thick I need the walls to be. I bought the slip from a local ceramic store. I let the slip sit in the mold for 22 min before pouring out the excess. *I have since been trying 30 min, and the walls are a little thicker I waited 1 hour to take the form out of the mold. Once this is done, I slowly shape the form by trimming the excess. My original design had many undercuts that I had to simplify the plan for the mold, so this is where I give it a shape I like (and where I can benefit from thicker walls) They looked great after a ^5 bisque firing. although here's where things get complicated… I don't have my own kiln, so I pay to glaze and fire at a local studio. I used underglaze transfers and my amaco velvet underglazes. I also used my own glaze on the base of one, and I like how it turned out. I chose to use the studio's clear glaze, which has been coming out with this funky opalescence lately. I dipped the entire blue flower vase decal piece, not the back, in the clear glaze. It was pretty thick, so I smoothed and thinned it out once the glaze dried. I also did this for the swirl, only dipped the in the clear glaze for the other one with the already glazed base. Results after ^6 firing: As you can see in the photos, the clear glaze I used was incredibly too thick and ran. The shaft warped and leaned onto the base and kiln shelf. The swirl decorated piece was fired after the first two and was elevated to see if that would help… not sure why they fired it without letting me know about the first two mishaps. In doing so, the entire base and shaft warped. I'm at a loss for what to do next. Here are some questions I have, and there are probably so many more that I may not have answers for. Is the issue the slip itself? Is it the timing of the casting and the thickness of the walls? Regardless, I am going to make the walls slightly thicker so I can trip and shape it better. Is it the form itself - I hope not because there was no warping after the bisque? Is it the glaze? The glazes at this studio have been inconsistent lately. Or is it the firing schedule of which I have little control? I'm talking to a friend who just opened his studio and will fire there next, and hopefully, he can adjust the firing schedule if it would help. Link to comment Share on other sites More sharing options...
Hulk Posted February 20, 2022 Report Share Posted February 20, 2022 Hi (again) Haley! I've no experience in, very little knowledge of slip casting. Sometimes a response gets things going for others, so. I'm not seeing any attached video. Kudos on the three piece mold, wow. Link to comment Share on other sites More sharing options...
Min Posted February 20, 2022 Report Share Posted February 20, 2022 Looks like there is a design issue, too much of an overhang from the end of the pieces to where they are supported. Just like bowls can slump when there is too much of an overhang from the foot or base to the rim of the pot. Overfiring and thickness of the work contributes to slumping also. Link to comment Share on other sites More sharing options...
Mark C. Posted February 20, 2022 Report Share Posted February 20, 2022 I think what Min said is also the issues -try making the molds less thick with less drying time with slip and glaze thinner as well . Thin the glazes The lower plate form is bending due to stress pulling it up and or glaze to thick or both Link to comment Share on other sites More sharing options...
Pres Posted February 20, 2022 Report Share Posted February 20, 2022 cantilevered weight of the longer appendage warps the base plate. best, Pres Link to comment Share on other sites More sharing options...
HaleyChoice Posted February 20, 2022 Author Report Share Posted February 20, 2022 Thank you all! I really appreciate your thoughts Link to comment Share on other sites More sharing options...
Jeff Longtin Posted February 21, 2022 Report Share Posted February 21, 2022 Two suggestions: 1) the point where the shaft meets the wall plate creates a weak spot. If you can make that spot more rounded it would give the casting more strength to support the weight of the shaft. 2) If all your attempts to solve this problem come to naught I would suggest you cast the two pieces separately. (And then attach them out of the mold.) That way the pieces will come out of the molds with their own structural integrity intact and its just a matter of finding a way to attach them that doesn't interfere with that. In the photos it looks like the wall plate is slightly deformed. This is a result of the fact that the two mold surfaces are close together and the slip is not completely draining from the mold. When this happens a slight vacuum is created and it causes the two clay surfaces to get drawn toward each other. Thinning the slip, so it drains completely, will help as will making the wall plate thicker so the slip has room to move, and drain, from the mold. Link to comment Share on other sites More sharing options...
Chilly Posted March 2, 2022 Report Share Posted March 2, 2022 On 2/20/2022 at 3:58 AM, HaleyChoice said: I bought the slip from a local ceramic store. I let the slip sit in the mold for 22 min before pouring out the excess. *I have since been trying 30 min, and the walls are a little thicker I waited 1 hour to take the form out of the mold. What is the maturing temperature of the slip? I find earthernware slip will cast in 20-30 minutes, but stoneware can take 50-60 minutes - temeperature and humidity depending. On 2/20/2022 at 3:58 AM, HaleyChoice said: They looked great after a ^5 bisque firing. Are you sure it was a ^5 firing, not a n^05? On 2/20/2022 at 3:58 AM, HaleyChoice said: Results after ^6 firing: Again, is this the right ^ for your clay? Link to comment Share on other sites More sharing options...
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