I'm finishing the scratchbuild tank I started way back, and starting on another spaceship. As I've discussed, I'm using water-putty to make the masters, silicone for molds and resin for the casts. In each of these materials I have to vigorously tap the respective container to ensure air bubbles don't form. I'm some cases, especially with the water-putty, I don't get all the bubbles out. To remedy this I cobbled together a crude agitator, inspired by a blog post on the Ultrawerke site.
First I bought a 4x6 inch wooden picture frame for a US$1.00 at the dollar store. I cut up the fiberboard backing to make legs to elevate the frame. I cut the bottom out of a cardboard coffee bean container, leaving a 30mm lip all the way around. I suspended the coffee can platform from the frame using springs from the hardware store. I then mounted a 1.5V motor to the side of the frame. The motor and associated wires, switch and power source were all left over parts from a graduate course I completed last winter but could easily be purchased from Radio Shack for US$5.00 to $7.00 total. I fixed a weight to the drive-shaft using epoxy putty and turned it on and to my amazement it worked. It worked a little too well and the frame starting scooting across the kitchen table. My wife suggested placing the whole contraption in a cardboard box, which worked beautifully.
I"m off to pour the top and bottom hulls of a new spaceship sculpt. I think this agitator will go a long way towards making more crisp scratchbuilds.