I decided to replace the original lousy Quantum rubber mold made in 2007 of my design, with a new Smooth-on mold since the Quantum rubber since the stuff was so poor it tore in all four corners within the first couple of casts made from it. I've been delicate with it and babied it along as well as repaired it numerous times.
So the photo is my plaster master set up to make the new mold:
The nice, strong Smooth-on mold all finished and a release applied to it for the next step:
The next step wasn't photographed as there wasn't much to see, but I made a Smooth-on positive mold of the above negative mold with 3-4 brushed-on applications to get it about 1/4" thick. Once I applied the last coat and it started to firm up, I filled the cavity with plaster and let it set:
Once it set I turned the whole affair over and carefully removed the negative mold rubber with it's four piece plaster shell from the rubber positive with it's plaster in-fill. Once removed I was left with the rubber positive with it's plaster mother mold in-fill supporting it inside:
Some might already know where I'm going with this next, for those who don't- the next step is making a form around it and casting what will need to be a five piece mold made from molding-plaster. While there's few undercuts in this design there are some, and future projects like this will have considerable undercuts. The rubbers' flexibility completely eliminates any possible adhesion as well as any issues with undercuts causing problems removing the five piece plaster mold from it.
I could have filled the whole negative mold up with liquid rubber but it would have taken about 2-1/4 gallons of it to fill, thus making it just a skin mold with cheaper plaster in-fill.
The plaster mold when dry will be used to hand-press the course red clay I use into it.
I've already put in my order for some other materials and added 200# of molding plaster so I'll have some on hand, that's supposed to come Friday, so next weekend I plan to make the plaster mold.
I already came up with a workable kiln schedule and tested it on two pieces similar in size to this, one of them was 2" thick solid clay, no cracks or blowouts.
I decided to go with:
Ramp up 80º/hour to 200º and candle for 9 hours.
60º/hour to 1200º which moves it through the water burn-out and quartz inversion stages nice and slow.
After that it goes 80º/hour to 1950º and ends with a 10 minute hold at 1950º @ 36-1/2 hours.
But that was to cone 04, I want to go to what would be cone zero if there was one- as that got the best color @ 2,056º so that will take 1-1/4 hours longer for the firing.
I expect the sculpture will weigh about 38#