I could really use some input. We have an air release mold system that I am adding a few dies too. The instructions are pretty straight forward but I am having a hard time with a couple of decisions on sourcing two of the materials.
1) The rubber for the models.
We are making the models in clay and then making master molds from them to be able to cast a new set of masters in rubber so that we can use these new masters over the years to remake the working dies.
The instructions I have to do this just call for a rubber urethane. There are tons of choices but I can find none that are specifically for mold masters. I was thinking of using Sharkthane Flex Pro 70-20 (2qt A/B 1-1 mix $35) that In spite of its name, sets hard. There are dozens of options and price ranges. I was hoping someone might have input on a good rubber for this purpose. Most seem to be flexible which for the mold itself would be great but for a master model I thought it should set hard. Is this a reasonable assumption?
2) The plaster for the working air release dies.
The instructions call for Ceramical but when I went to buy it my local supplier assured me that Hydrocal was fine since he didn't have Ceramical. Since this happened last summer (I know, I know) I need to toss the Hydrocal I bought then and buy fresh so I was researching the issue to make sure. I did find this link:
and they are clearly not the same but I was hoping someone could chime in if they have used such a substitution. My local supplier has a bag of Hydrocal for $25 but the only source I can find Ceramical is on the other coast and it is going to cost $60 to ship me a $30 bag of the stuff. i'll spend the hundred if I need to but obviously would like to have a local $25 source.