Mold experiments, day 4

I saw The Hobbit on Saturday. I was extremely disappointed. Further details in another post.

Mold 2, Side 1:
Material: DAP Silicone caulk, catalyzed with Delta Ceramcoat Mediterranean Blue (10 drops), approx. 1/4th cup
Matrix: Van Aken oil-based non-drying clay
Cure time: 12 hours
Size: 2″x3″
Mold frame: 3 legos high

This was the first mold attempt with Van Aken, and also the first using legos as key pieces.
Outcome: Botched application of silicone.Parts of the side, bottom edge, and areas around the master did not receive enough silicone – I didn’t press it down hard or well enough – and the silicone became lumpy and missed areas. Key blocks turned out very nicely, however, and the Van Aken made a good and pliable surface with which to work.
This mold was also slightly shallower than the master required.

Mold 2, side 1 redux:
Material: DAP, catalyzed with 8 drops of Med. Blue, approx 1/3 cup (previous mold too thin)
Matrix: Identical
Cure Time: 14 hours
Size 2″x3″
Frame: 4 legos high

On demold, discovered that the clay had picked up a pretty hefty amount of acetic acid, and had a surface consistency change. Airing it out on the back porch; this gives me concerns about future plastic molding, however, as having that much acetic acid right against the curing surface will likely slow the exchange reaction even with a catalyst – possibly ruining surface detail. Silicone partially rejected the catalyst; pockets and chunks of paint are visible, and the mold is more transparent than normal. Increasing paint amount for next cast.

Mold 2, side 2:
Material: DAP caulk catalyzed with 15 drops (better safe than sorry..) of Med. Blue. I’m also using almost a half-cup for this cast.
Matrix: Mold side 1(bis)
Mold release: Mann ease-release 200
M.R. Application: heavy spray, brief brush over master, second lighter spray
Cure time: intended 11-12 hours.
Frame: flipped previous frame and poured into bottom
Size remains the same. Final mold will be just over 1-3/4″ deep.

My master is vinyl, so I’m worried about possible damage to it from the M.R. We’ll see in a few hours.
Edit: no visible damage to master on demold.
Mold release failed; the mold halves were stuck together, and once again only the differing densities and shear line allowed me to get them apart. Will first try a heavier application and letting it sit longer, before switching release agents.
The silicone also had some foaming and detail loss, as with last time. The key blocks were filled incorrectly, and there were some potentially really nasty flash areas around parts of the master.
This is by far the thickest area/mold I’ve tried to cast: I suspect I may have to build the next mold half in separate sections instead of in one go, further complicating the mold release issue. It also looks like the thicker (viscosity) silicone may be complicating the casting process.

Further testing suspended until after Christmas. Will try a cast to see how buggered Mold 2, Side 2 really is..

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