Hollow silicone hand?

[AndyJ]

This is baffling me, even though I'm sure its done a million times every day.

Lets say you have a lifecast of a hand. You want to make that hand animatronic (tentacle mech, whatever.) How would you do a hollow silicone "skin" of it?

Even with a two piece mold, it's way too narrow to touch up any clay to even make a core plug.

I feel dumb?

 

[alans22]

While I don't have a specific material to suggest I imagine the process is similar to making a latex or rubber mask. I myself have done this with good results, so here's how I did it:

1. make your model, which it sounds like you've done.

2. make a two part mold of your model that is firm and has the pour spout at the place you want to be open. In your case this would be the wrist. (Now this is where your scenario differs from mine. I made my two part with hydrocal on a clay model. If your model is already cast of plaster or something firm you'll have to figure something else out; which I'm sure won't be too difficult to find with a search on mask making)

3. After you have a durable two part mold complete with the original model removed you will want a material that drys relatively quick and is flexible. I used latex, but I know there are nicer more durable and detailed materials available.

4. *Now pour enough of this material into the open area (the wrist) to do a nice even coat of the whole interior and perhaps use a brush to work the material into fine details. You then invert the mold and pour the remnants into a vessel with a lid to be used later. You let this thin layer dry and repeat, repeat, repeat (you can thicken and use a brush as you get further away from the details).

(*An alternative to this method is to totally fill the mold to the brim and let it dry a little bit, supposedly it will dry from the sides to the center and you'll be able to see the color change enough to gauge the thickness. After it's as thick as you want you can pour out the remnants for a future project. I have not tried this method but I think it's supposed to be easier although more expensive and probably reliant on the proper materials.)

5. After you decide you have a thick enough skin lightly dust the inside with talc or baby powder (this keeps the interior from sticking to itself) and pull it from the mold. Viola! Then paint and trim till you have what you want.

I hope this helps, it worked for me surprising well for my very first foray into making a mask. At the very least I think it will help you search and get better information.

Best of luck!!!opcorn

-Alan

 

[Duncanator]

You could try to do it like a slip mold in pottery making. You pour the silicone or flexible urethane into the mold, slush it around to coat all the surfaces and then pour out the rest. That would give you essentially a glove of rubber. Repeat the process if you want thicker skin.

Or you could do it as a roto-mold if it's sealed up.

Or you could wrap the armature with thin latex sheet, insert the armature into the mold, and then pour in the silicone or flexible urethane.

It depends on what you're trying to get.

 

[Mr Mold Maker]

Lets say you have a lifecast of a hand. You want to make that hand animatronic (tentacle mech, whatever.) How would you do a hollow silicone "skin" of it?

Even with a two piece mold, it's way too narrow to touch up any clay to even make a core plug.

I feel dumb?

To make your core take your two piece mold and lay up WED or white clay in the thickness you want your silicone to be. Trim the excess clay off right at the seams, give it a quick spray of sealer and release, and put the two pieces together. Pour your core material in (stone, resin, epoxy, etc) and let it cure. Take the mold apart, clean out the clay and touch up the seam and any problem areas and boom, you've got a core. You may want to make it a collapsible core depending on the pose of the hand, but that isn't something I can explain over text alone.

 

[AndyJ]

To make your core take your two piece mold and lay up WED or white clay in the thickness you want your silicone to be. Trim the excess clay off right at the seams, give it a quick spray of sealer and release, and put the two pieces together. Pour your core material in (stone, resin, epoxy, etc) and let it cure. Take the mold apart, clean out the clay and touch up the seam and any problem areas and boom, you've got a core. You may want to make it a collapsible core depending on the pose of the hand, but that isn't something I can explain over text alone.

Thanks for this. I guess I wasn't thinking of something as soft as WED, I was thinking more like a Monster clay and was worried there would be a very tiny seam material could get though. Makes sense!

(*An alternative to this method is to totally fill the mold to the brim and let it dry a little bit, supposedly it will dry from the sides to the center and you'll be able to see the color change enough to gauge the thickness. After it's as thick as you want you can pour out the remnants for a future project. I have not tried this method but I think it's supposed to be easier although more expensive and probably reliant on the proper materials.)

Your whole method is actually smart too, and would require less effort overall but be more expensive. Once you have a latex skin you could pour stone in, and just cut off the latex. You'd be left with a core.

Now I can help YOU in my own thread as long as you're using a casting latex like 407 with a stone mold, you can indeed just fill up the whole mold and let it set for an hour or so, the plaster will cause it to cure only at the edges. Then just pour the rest out and let it dry.

 

[Jasonium]

I did one a few weeks ago that ended up really good - captured fingerprints/wrinkles etc There is probably a better way but I made a one piece mold out of alginate - then I slush cast around it a few times, broke the mold off and hey presto! a hollow hand.

 

[AndyJ]

I did one a few weeks ago that ended up really good - captured fingerprints/wrinkles etc There is probably a better way but I made a one piece mold out of alginate - then I slush cast around it a few times, broke the mold off and hey presto! a hollow hand.

Did you use any thinning agent in the silicone? Thanks.

 

[Jasonium]

Hi Andy,
i wanted a solid hand so I used a resin mix.

 

[Mr Mold Maker]

Keep in mind that latex will inhibit platinum silicone. Even very minute traces of it trapped in the mold can prove disastrous, and fully inhibit the piece. While you can make a latex skin and pour stone in to make a core, you limit yourself to tin silicones or gelatin.