After so many months of trying to figure out how to make the foam patterns, it is time to move on to the next challenge: casting the hblb. I've tried several ways to do this, but haven't quite perfected any of them yet. The first four pics show what I thought was going to be a tremendous success. Investing the foam model in 50/50 plaster/silica flour mix and then dissolving the foam with acetone. Well, the plaster is so thick that it never quiet dried completely, so every time I poured one, the moisture would cause bubbles in the casting. Great idea, but it didn't work.
Another shot of how I setup the foamy to be invested. Carpet tube is quite handy for this.
I only had a few minutes before the plaster was too thick to pour, so I filled each mold and then put it on the vibrator for a few seconds to make the bubbles come to the top.
Here is the mold after I dissolved the foam out with acetone. This worked really well, but the center core just had too much moisture in it and I don't think it would ever totally dry out.
So, for the next idea, I built a spray booth and tried spraying the plaster/silica mix onto the foamy. This worked ok, but I wasted too much plaster. It also was very messy and a pain to clean up. Dipping the part worked much better.
Here are three foamies just after the dipping process.
Another shot of the foamies.
I'm going to try to pour these today. The plaster completely dries overnight, so I only have a one-day turn around on the part. I can't wait to see if this works!