This is a glob of hard "Playdough" painted black. It's 1 part cornstarch, and two parts baking soda, 1.5 parts water. Bring to a boil and it polymerizes. I did it in the microwave. At that point it's very rubbery, but you can roll it and treat it like clay, with some difficulty. From there it's just a mater of curing it to be hard. I microwaved it to get it hot about half a dozen times then let it cool in-between. The finished bit is very hard, pie dough colored, with a coat of paint for looks and water protection. It's probably a bit more brittle than wood, but you can form it. This is probably good enough to RepStrap many of the Darwin brackets, though it'd be tough to get enough detail for the gears, and it might not be strong enough for the corner brackets.
