Casting hands question

[JMC]

Hi,

I just got my trial kit from smooth on and want to cast a pair of hands. I made a one piece mold and tried casting a strange spell hand. well, i followed the directions and got a hand but....the fingers! where are the fingers! I thought the resin was liquid enough to get into the tiny finger holes in the mold but nope. Anyone have any tips on casting open finger hands? I did okay with the fists.

any help would be welcome

[boss]

a pressure pot would definitely help here. even though the smooth-on resin is very "liquidy", air pockets will form when you're trying to cast something so small.

[JMC]

How does it work and is it expensive?

[BlackKnight]

[boss]

How does it work and is it expensive?

I don't have one, so I don't know. but I believe it works by crushing the airbubbles.

[JMC]

Force...huh..? lol...

[ctc]

Hmmmm....

I carve lots of air canals for stuff like that. For a hand I'd DEFINITELY use a 2 part mold. A little talcum powder helps too. Powder the inside of the mold before using it.

Don C.

[JMC]

Thanks, I will try that. Btw, I just tried using a syringe! and except for one small bubble, it seemed to work. I made a one piece mold from an old 35mm film container and injected into it...don't get gross... anyway it worked the first time out. I don't know if that will be of any use to anyone but I'm throwing it out there.

[ctc]

>I just tried using a syringe! and except for one small bubble, it seemed to work.

Injection molds; works really well, but you gotta plan them out a little ahead of time. I use 'em a lot; but for the injector get one of them syring lookin' thingies for giving babies medicine. They're bigger. If you need a smaller nozzle, attach one of those extra nozzles you can get for model kit tube glue.

Don C.

[jessica]

Don do you think I could try the injection for a sword that I made...or do you think dusting the two part mold would be better?

JMC--can you re-use the syringe?

Here's the sword I need to mold and cast:

[ctc]

>do you think I could try the injection for a sword that I made...or do you think dusting the two part mold would be better?

Swords are a huge pain to cast, 'cos air gets trapped in the blade since it's flat and doesn't allow a lot of mobility. If you're using an injector I find it's best to vent the heck out of things. That way the air has somewhere to go when it's forced out. Powdering the mold never hurts. I usually shake 'em a bit after I fill them, to help move some more air.

>can you re-use the syringe?

I use easyflo-60, which doesn't stick to the plastic of the injector. Eventually the heat and expansion/contraction wears 'em out. But you can use 'em dozens of times.

Don C.

[jessica]

Ugh...I was afraid of making casts of the blade...I was even going to do simple one sided molds and glue them together--but didn't know if that would suck or not...I do really have to make a mold and cast the sword, since who knows how long the balsa would lay true and straight...

[ctc]

>I was even going to do simple one sided molds and glue them together--but didn't know if that would suck or not

Odds are it would suck. It's tough to fill molds like that.

>I do really have to make a mold and cast the sword

Yup. Shouldn't be too tough, so long as you've got enough plasticiene and lego.

>who knows how long the balsa would lay true and straight

I use cheap nail polish to seal the balsa wood. Put on a few coats and sand it with fine sandpaper and it'll last a little longer.

Don C.

[jessica]

Great stuff Don! I'll be protecting the balsa tonight from future warping...that will buy me some time at least...

[JMC]

Hi,

I just run the syringe under warm water and gently scrape out the extra smoothon. You get them cheap at an art supply shop.