I made the mold as a single one-part. I began by applying a tiny amount of modeling clay along the edges, firmly pressing the model onto an acrylic sheet, and then trimming away the excess clay that was displaced to the outside of the model at the bottom edge.
I built a mold box out of acrylic sheets and 3M gummy (temporary) hot glue.
I did a first pour with rapid-cure Smooth Cast 300Q to pull out some finger and clay oils and other junk that got in there when I cleaned it after the mold had cured. I didn’t want to waste a first pour of the expensive crystal clear knowing it would come out with a cloudy surface.
For my first test pour I measured out half the volume of the mold in clear resin and put in the vacuum chamber until all the gas had been removed. The 20 minute pot life of Crystal Clear 200 makes the easily possible. I then put the first half in the pressure chamber and let it get to the gel stage at the end of its pot life. I then depressurized and tossed in some junk electronics components. The resin was still gooey at this point, but viscous enough to hold the components up in place. I think it was at about the 30-40 minute mark after having mixed the first half of the resin. I then poured the second half and re-pressurized. I wasn’t being super careful about bubbles and could manually pop them in future before re-pressurizing, but even with that, I am pretty happy with the results of the first test. I’ll do some cleanup work later with the pneumatic random orbit sander to clean up the flashing, plane the back, etc, but the crystal clear surface remains tacky for a few days after the de-mold time has elapsed (assuming you don’t have an industrial oven to finish cure it, which I don’t), so I wanted to leave it alone for a while.
There is a very faint dividing line between layers, but so faint that you’d never notice it unless you were expressingly turning it around under a light looking for it.
I’m pretty sure I can eliminate those final few bubbles on my next pour. Popping them with a pin would work, but I think a quick spray of mold release should do the trick. I just didn’t have the can with me. It breaks the surface tension and tends to eliminate surface bubbles on one-part molds really well. (But don’t do this for the first half of the pour!!)
I just wanted to get a quick experiment out of the way first to get a sense of the main challenges. It’s not perfect yet, but this first try actually went way better than I had expected!