Experiments in Casting

A while ago, I picked up some Alumilite Silicone Mold-making materials, but never got around to using them. I've never done anything like this, but was inspired by what was possible based on what I saw on the site here.

Last month I finally worked up the nerve to try. Everything felt successful, but when I extracted my master, I could see that there had been a bubble right where the mast was supposed to go.

This is my next attempt.

Attachment 50885

In this picture, you can see all of the goodies needed. I have my Alumilite base, hardener, and measuring cups. The small metal measuring cup is my mold box. The large one is for mixing. In the shadow of it all is my master on its stand; a cutter from Langton Miniatures.

Attachment 50886

A close up of the cutter. The thing to be reproduced needs to be sunk 1/4" into the resin, hence the stand. I built the stand to center the hull in the middle of the measuring cup.

Attachment 50887

At this point, I have thoroughly mixed the silicone and hardener. The master has been placed in the cup and taped so that I can tilt the cup while pouring the resin in. Hopefully this will get rid of the offending bubble this time.

Attachment 50888

I have poured the silicone. To either side of the mold-in-making are the halves of the mold with the bubble. I cut the damaged mold in half to inspect it. If you look really close you can see it where the mast would attach. Other than that, I am really impressed with the level of detail!

Cross your fingers! It takes 18 hours for the mold to harden...

18 hours have passed.

Attachment 50895

The tape is off.

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The mold is extracted from its tin.

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The cutter returns to the light of day. Unfortunately, while better, the bubble persists.

I wonder if vibrating the mould might release the bubble Dobbs? As an aside that is a nifty Band Saw you have there. ( :envy:Bandsaw envy)

Rob.

Quote:

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Originally Posted by Bligh

I wonder if vibrating the mould might release the bubble Dobbs? As an aside that is a nifty Band Saw you have there. ( :envy:Bandsaw envy)

Rob.

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You are entirely right, Rob. I checked out some silicone mold help sites and that was their recommendation. Also, pouring some silicone on top of the piece to be cast and spreading it
into the nooks and crannies before immersing the piece. Also suggested was talcum powder, but I only have baby powder made with cornstarch. We'll see if that makes a difference. 18 hours to go on the next try...

Just to see what the next step was like, and get a jump on any challenges there, I went ahead and cast a hull in my bubbled mold.

Attachment 50901

I was very impressed with the results. I quickly dabbed some paint on to increase the contrast. Once I work out the bugs/increase my skills, this is going to be very satisfactory!

Your comment about talc set a bell ringing dobbs. About 25 years ago Capt Kiwi and I did the battle of Trenton. Someone suggested Talc for the snow so we covered the house roofs and roads ,trees and bushes with it. Our wargames mats et al smelt like a house of ill repute for a year after the game. Bad idea!
Rob.