Hydroshrink vs Hydrospan

[stuart]

Which gives the best results? Is it better to shrink down a larger piece or expand a smaller one? I would like to make "Clone Wars" figures, but can only find heads that are way too small (like 3 1/2" the mini figs), or way too big (bobble-head sized or the Pez heads). Thoughts anyone?

[LonnieFisher]

Hydrospan 400 shrinks and it works good. Hydrospan 100 grows and works good, but it is hard to secure it to make a mold. Usually bigger heads have better detail in them. So I would go with the Hydrospan 400 for a better looking end result.

[David Lee]

Which gives the best results? Is it better to shrink down a larger piece or expand a smaller one? I would like to make "Clone Wars" figures, but can only find heads that are way too small (like 3 1/2" the mini figs), or way too big (bobble-head sized or the Pez heads). Thoughts anyone?

I have done several projects with both. I find that the 100 (enlarging urethane) is easier to work with. The 400 (Shrinking urethane) is a bit trickier and requires a pressure casting and a dehydrator to get really good results.

If you can cast the 100 under pressure it will give much better results and a more even expansion. Sounds like the trooper helmet will expand fairly evenly (no protruding elements), so you should be able to remove it as soon as it gets to the size you want.

Anyway, hope this helps... the folks at Industrial Polymers are very nice as well.

-Dave

[Blackkryptonite]

I've used both a little and they each have their pros and cons. 100 doesn't cure as fast but it's thick and like LonnieFisher said it can be difficult to get in every nook and cranny of the mold. I usually brush the inside of the mold with a thick coat of it and then use the poor man's spin cast technique to get all the bubbles out. 400 cures in under a minute but the colder you have the mix the slower it cures. So if you're able to work inside a refrigerator when you're mixing it be prepared to work fast. 100, IMO takes less time to grow than 400 takes to shrink.

Blackknight might have some helpful tips though, as he seems to be the one that has used both of them the most.

[LonnieFisher]

The pot life is so short I don't like either of them. Pressure casting seems like a good idea. But with only thirty seconds to work I would take too long trying to get it in the pressure chamber. I wanted to make a pressure casting chamber, but I'm kind of broke and can't afford one. I made a vacuum chamber out of a pot and piece of thick clear acrylic or plastic and vacuum pump. It works pretty good for silicone degassing.

[LonnieFisher]

I found cooling your 400 before mixing with water made it hard to mix because it was so thick. I thought about going to a pizza place my friend works at to mix it in the walk-in freezer, but I'm sure it would be totally illegal to do around the food.