I have just purchased some alginate and plaster to make some death masks for small mammals.This will be my first time making moulds.I plan on lowering the heads into a cup of mixed alginate,but how far can I lower the head in?If I go beyond the base of the animals head,is the alginate flexible enough to get back off?Also on small mammals like squirrels,mink,marten...etc. will the alginate pick up the small details of the inside ear and is this done with the head dunk method or should I use a dam for each individual ear?Thank you,hope you can help me.
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be careful how severe the undercut you subject it to is. If you submerse it fully in the alginate it will likely tear as you demold. I never subject my pieces to more than say 3/4 inch of stretching before I suspect a tear. If I have a piece needing to go beyond that point - I make a multi part mold. In your case - I would dam around the head and make it in two parts with the division running down the bridge of the nose and back of the head. That way you don't have strong undercuts AND if you mix your alginate to the right consistency it will flow down into the ear and get all that detail where with the dunking method you may get an air bubble instead of ear interior. Gravity will help you here and alginate flows down a lot better than sideways.
Hope that helps.
Alginate gets pretty hard. It is the same stuff dentist use to make hard molds of teeth. Afriend of mine makes his own duck heads. He uses silicone, Pours it into a cup and puts the head in until it sets. After the silicone has set it has more than enough give to pull the head back out. Now he has a mould that he told me he has used over a hundred times. When ever he needs another head he just fills his mould with a secret liquid (he wouldn't tell me what it was) after it gets hard he puts a screw into the back of it and pulls it out. I know silicone is expensive, but it is durable enough and last long enough to pay for itself in just a few moulds.