Spaceship Factory Gone Berserk

My very first foray into mold-making involved attempting to use automotive gasket-making RTV silicone as a cheap alternative to dedicated 10:1 silicone.  The logic was that since this gasket-making silicone (pictured below), also known as "red RTV", resists the heat of a car engine it would be perfect for casting with hot metal.  Unfortunately my first attempt showed me how unmanageable that silicone is to work with.

I've made quite a few silicone molds since then utilizing Alumilite's HS3 10:1 silicone, with some successes and some failures.  Regardless of the outcome the fundamental take-away each time is that mold design, with regard to air-flow, dictates success and failure.  Armed with my new knowledge, I decided to try some more experiments with the red RTV.

My attempt at making a two-part mold using this RTV failed.  Even with a mother-mold around the two rubber mold-halves the casts just didn't come out right.  Most of the time the halves didn't line up right and the metal leaked out, but the few times I got the mold to fill resulted in massive amounts of flash.

I abandoned that dream and decided to attempt a one-sided mold.  This is where this RTV shines!  I laid down a bead of rubber in a container (scrap plastic from a milk jug) and gently but firmly pressed a spaceship miniature I sculpted into the RTV silicone.  I then put it under my 34 watt lamp to accelerate the curing.  This rubber is terribly sticky and impossible to brush or spread on, but is very easy to press objects into.  Unlike window caulk silicone, this rubber comes out of the tube with very few if any air bubbles.

I pulled the spaceship miniature out of the rubber 24 hours later (versus 48 hours with the 10:1 silicone) and the mold captured every detail.  Whenever I mix up water-putty for a new spaceship design, I use 2.5 teaspoons of putty and 1 teaspoon of water.  This may sound like a miniscule amount, but out of that amount I actually only use a thimble-full of putty mix for a 60mm to 80mm long spaceship.  I therefore always have extra putty I need to get rid of that I'm loathe to waste.  I can use these one-sided molds to make casts using this extra putty and increase the size of my fleets geometrically.

The two pictures below show an example of this.  I mixed some putty for a new destroyer design twice, once for the upper hull and once for the lower.  I also mixed some putty up for a mother-mold for a separate mold experiment.  Each time I poured the excess putty in the red RTV mold pictured below.  Now I have three new ships!  Since this mold was an experiment I only made a mold of the top half of the ship, but in the future I will mold both the top and bottoms separately and then pour excess in each mold, finally joining the putty halves with a few drops of CA glue.

The advantage of this silicone is its cheapness, $5.00 or so, and availability.  If I want to go grab a tube of red RTV at 2AM, I only need to drive to Walmart.  Since I don't plan on casting in hot metal using this rubber, perhaps I'll try one of the other colored automotive RTVs from the same manufacturer.  I'm off to buy another tube; I plan on making molds of my missile counters.

Good view of mold

Better shot of ships, crappy shot of mold