Plaster Pain in the Aster- PP II Will Be Faster

Sometimes you just don't have enough time to try out new materials in advance. It became so time-consuming to try and figure out how to make a mother mold with Hydrocal FGR 95, that I had to table using it for now. Midway through trying it out, I realized I had completely forgotten that I was going to go the next level and make Forton, not just use straight Hydrocal FGR 95. As it turned out, I'm glad the other Forton ingredients didn't go to waste during this trial period.

It was a horrible mess. Splatters of plaster had to cleaned off every nearby surface the next day. It was very difficult trying to get it to stick as I applied it to the castor oil/alcohol coated latex. It starts out very runny. I used hot water to speed up the curing. I added extra Hydrocal to my first bucket so that I'd have a thicker mixture for the initial application. There wasn't much change for a long time, then suddenly there I was rushing to finish applying it when it started to thicken. The thickening, heating up stage is known as "going off'.

As it started to thicken, I was able to get globs of it to stick by throwing flicks of plaster at it with a paintbrush. This made a big mess. In retrospect, I needed to have covered my support surfaces with duct tape and petroleum jelly, as Tamar Bonet suggests in her excellent mold making tutorial.

For the next layer, I tried to apply the fiber I'm using. When I pressed it against the surface to flatten it, the first layer of plaster broke up in pieces wherever it covered foam-covered latex. Before I could figure out how to work around this new problem, the remaining plaster hardened to unworkable. I could no longer adhere it to the fiber as it hardened. I had to leave it to harden unused in the bucket. I knew I could clean it out of the bucket by leaving it to set up until the next day, then popping out the whole mass after a few firm taps on the bucket. By then, I had used up enough plaster on practicing that I faced another long delay if I decided to order more. It meant waiting for a new bag of it to be shipped to me and further struggles from within the learning curve.

I had to come to a decision. It was hard to do it, but I knew I had to take all of the plaster off of the latex before it hardened more and became extremely difficult to remove. I had to hit it with a hammer in one area where it stubbornly refused to pull free. I hope it was due to not enough parting agent there, and not because of undercuts. I have scrutinized it and can't see any undercuts.

After the plaster removal, I wiped off all of the castor oil and have washed the surface a few times since. Chips of plaster that still fall onto the latex are
being vacuumed off periodically. Mainly, they've been falling off the plastic I use to cover the model. Just when I think I've gotten rid of all the little plaster chips, more of them show up on the latex. Sooner or later, I'll win this fight! :)

As soon as I was able, I hurried up and ordered some Plasti-Paste II to use instead of plaster to make the mother mold. While I'm waiting for it to arrive, I need to buy wood for support legs and figure out how I'm going to attach and hold them in place on each mother mold section while the Plasti-Paste II cures.

Support legs are a handy feature. They serve as a built-in stand for the 
whole mold unit when it's in inverted position, ready to receive the casting 
material. Plasti-Paste II has strong adhesive qualities and will glue the legs in place permanently.

I'll need to work out how I'm going to level the mold by adjusting leg heights. Thus when the mold is inverted, it will sit firmly and evenly on all of the legs. There are a few ways to do this. One is done as the legs for each section are added. The idea is to afix a board atop the whole mold unit. The board is leveled according to how the legs will meet the floor. It is supported at the height which will be the space between the legs and the floor when the mold is inverted. One end of each leg is attached to the mother mold. The other end is cut to the length which meets up level with the board's underside.

The other approach is to adjust the height of each leg after mother mold making is done. First the legs are adhered in place, each section at a time, but left at uneven heights, and the Plasti-Paste II is allowed to cure. When all mother mold sections are done, a spirit level is used to cut the legs to a uniform height. One artist has successfully used this method on large molds like mine, using a Sawzall to cut the legs.