Molding and Casting Kanohi/Krana/etc?

[SixFootBlue]

Hello BZP! I'm hoping this is the right section for this sort of thing.

I've been a long-time lurker, on and off since as far back as 2006. One of the things on BZP I was fascinated by was Flintsmith's custom cast kanohi and krana. Now that I've grown up a bit, and have the means to actually obtain the materials I'd need, and the knowledge to use it properly, I started delving into it myself.

I made some DIY silicone molding putty and was able to reproduce a krana out of hot glue for a test run.

http://i.imgur.com/iBlL0aD.png

It turned out pretty nicely, despite taking four attempts, and it fits onto the toa head perfectly. I'm hoping to move on to using either resin or polymer clay to cast actual kanohi, since hot glue is rather flimsy and a bit fragile.

Though I have a couple questions for anyone who has experience with this sort of thing.

1) If anyone's been successful at using resin with two-part mask molds, is there any effective method of eliminating air bubbles? One thing I noticed with the glue krana is that there was actually a fairly large air bubble embedded inside.

2) Is silicone caulking oven-safe? The mold putty I made was a mixture of GE All Purpose Silicone I, Corn Starch, Acrylic paint, and a little bit of baby oil. The polymer clay I have my eye on is fimo, which cures at 110C, and the silicone I bought is resistant to at least 200C-250C. Looking over MSDS sheets for GE silicone, it looks like it releases formaldehyde when you exceed the recommended temperature, which is worrying.

Thanks!

[Maphrox: Toa of Polygons]

From what I know about resins, bubbles are pretty much only possible to eliminate by mixing carefully.

 

Everyone who works with resin hates bubbles.

[Crunchyn]

There's several ways to approaching the air bubbles problem. Like Maphrox said, the casting material must be carefully prepared and mixed to avoid air bubbles. Then you could invest in a pressure pot to put the mold under pressure forcing the air bubbles out. When it comes to the mold, preparing gates is important as they help direct the casting material through the mold to ensure full coverage and not get trapped. That is likely the issue of your hot glue cast as I remember from my own slush casting with hot glue, the glue is rather thick and cools quickly, so it wasn't able to get into all the areas right. (also hot glue tend to have air bubbles in it anyway, especially if using a glue gun.)

[SixFootBlue]

Gates are something I need to practice integrating into my molds, yeah. I made the glue krana by squrting the glue into one half of the mold, then in some of the narrower depressions in the other half, then I pressed the two halves together before the glue set, and left it to cool, so that's probably where the bubbles came from, since the air had nowhere else to go.


I'm still looking into whether or not the putty I made is oven-safe or not, because I kind of feel like polymer clay would be easier to use as far as masks go.