Making a mould of a foam appliance?
- Thread starter Vandark
- Start date
Harry Harris
Well-Known Member
Because of the fragile nature of the foam applicance I'd use alginate on it, with a plaster / plaster bandage backing, then cast that in a fine detail plaster and take the silicone mould off that.
Harry
Harry
Although silicone is great for catching detail, that can be a curse. If you miss a spot on a wood pattern and don't seal it correctly it can grab like a vise in the grain.
Although I have not cast a foam appliance with Silicone, I could see it grabbing like it can on wood.
I also believe the alginate/plaster would be your best bet.
Although I have not cast a foam appliance with Silicone, I could see it grabbing like it can on wood.
I also believe the alginate/plaster would be your best bet.
Reactor drone
Well-Known Member
Foam rubber is basically a sponge so if you are going to try it,sealing would be needed.It would also be better if the piece was mounted on whatever it was designed to be glued to(eg-head cast)in order to preserve the original form of the sculpt as much as possible.
I think sealing it would destroy the original piece. Go with alginate.:cool
Vandark
Sr Member
Why would an Alginate (something like Smooth-On's Alja Safe?), be safer to use for this project than something like Smooth-On's Rebound 25 silicone rubber?
Reactor drone
Well-Known Member
The silicone will get into the pores and form to the surfaces very tightly so you're likely to remove a lot of the foam latex,which has a low strength,when removing it from the silicone.
Alginate is softer and more breakable than silicone and the water might also tend to wick into the appliance leaving the alginate more on the surface.
I just did a small experiment on a piece of painted and unpainted foam latex with dental alginate and it came away cleanly from both pieces with good detail.
Alginate is softer and more breakable than silicone and the water might also tend to wick into the appliance leaving the alginate more on the surface.
I just did a small experiment on a piece of painted and unpainted foam latex with dental alginate and it came away cleanly from both pieces with good detail.
WOW, that worked great! What's the best material to use for casting from alginate besides plaster since water is the enemy to urethanes and resins? I know alginate retains alot of moisture for a while before it starts shrinking and drying/cracking.
Vandark
Sr Member
The silicone will get into the pores and form to the surfaces very tightly so you're likely to remove a lot of the foam latex,which has a low strength,when removing it from the silicone.
Alginate is softer and more breakable than silicone and the water might also tend to wick into the appliance leaving the alginate more on the surface.
I just did a small experiment on a piece of painted and unpainted foam latex with dental alginate and it came away cleanly from both pieces with good detail.
Normally all this would just be trial and error, but because I can't damage the original, makes it a bit harder for me.
Is the algenate tough enough not to tear when demoulding if something is stuck deep in there?
BTW: Thanks for al the help!!!
Alginate does shrink when it dries out. You have to keep it moist with wet paper towels untill you're ready. Pat it down to dry the water on it and use ultracal 30 to make the cast. I almost forgot. You should put a plaster bandage mothermold on the alginate before removing it from the piece. That will help it support the shape of the mold.
Depends on how deep the undercuts are. Most latex pieces are designed so they don't have undercuts. Makes it easier to demold.
