My mask had some extra-scary work done. I used a scrollsaw to cut an MDF divider for the mask and bolted it together so I could start making the hard mother mold out of Smooth-On’s Plasti-Paste. I then rubbed the whole rubber mask down with Sonite wax and sprayed it with Ease Release 200 so I could remove the subsequent layers easily.
And then it was time to start heaping that stuff on! Plasti-Paste has a consistency, texture, and stickiness all comparable to applesauce while it’s freshly mixed. Kinda gross. Extremely annoying to work with but also gets the job done pretty effectively.
It sets very quickly, and you can apply coats over it while it’s still tacky. I spent about an hour and a half getting it all over my clothes, my work surface, and occasionally even the piece I was working on! When it came time to do the final coat, my girlfriend had the bright idea of tamping everything down with paper towels and letting them be the outer surface, because this stuff tends to dry somewhat spiky and hard to handle otherwise.
Then I broke it apart, peeled the rubber off, removed the master, and bolted everything back together!
All things considered, this is probably way overdone for the size of the mask that I’m casting, but this is the first time I’ve made a mold in this fashion, so I was trying to be a bit overcautious. I immediately threw caution to the wind, though, and started trying to slush cast Smooth-On’s 65D, pictured here:
Look at that! It worked! There’s some black speckling on the white cast where the paint transferred off the master onto the mold and then onto the urethane resin. Gotta get my technique down so the back of the mask is a bit smoother, but the finished part is strong, caught all the detail, and doesn’t have too much in the way of bubbles on the surface for me to fix. I might try brushing the first layer of my next cast on to see if I can reduce or eliminate the air bubble issue on detail spots like the rivets and the screws.