Alumilite RC-3 Problem

[lamont]

I have never run into this problem until now. I usually cast Smooth-On 305, Insta Cast and Crystal Clear 202, but this time I am trying Alumilite RC-3. When the resin has begun curing the resin level gets lower in the corners and I end up with "clipped" corners. I tried dragging some excess resin beyond the mold edge in the corners with a stirring rod, hoping, resin would get drawn down into the corners when the resin level sinks, but it's not working. That's a platinum-cure silicone mold (2258) and I use Mann Mold Release 2000, in case it matters. Please examine the "clipped" corners in the image that I took.

I have tried casting with chilled (fridge) resin to slow doen the curing proces, but the "clipped" corners are still happening.

Has anybody here who has used RC-3 run into this problem? Any advice? Thanks!

[mangozac]

From what I've just read RC3 is a very low budget resin, so I expect that you're just experiencing shrinkage as it cures. Corners will be the first areas it pulls away from.

[lamont]

Well, RC-3 is much more expensive than Insta Cast and about on par with Smooth ON 305. Neither of the latter two resins exhibits noticeable shrinkage. In very shallow molds, RC-3 does not show the problem either. Other than cooling the resin, which did not make any difference, how can I slow the curing process?

[RageofAchilles]

Try multiple pours of thin layers into the mould, if you don't see the shrinkage then it's probably a problem being caused by the heat generated in larger pours. This causes some of the resin to evapourate in the curing and causes shrinkage. Sometimes in a closed mould the same problem will cause resin expansion instead, as the gases try to escape.

A problem more common in general purpose urethanes

[lamont]

[RageofAchilles]

Excellent news!