Need advices on Batman Cowl - cast in fiberglass, latex and plastic

[regisaugusto]

Hi there people. Some time ago, I finished a fiberglass batman cowl, based on a pepakura model by Ruze789. My intention was to cast it in three different materials, according the following plans:

1 - negative mold in plaster / positive in latex
2 - negative mold in silicone / positive in fiberglass (for displaying purposes only) / another positive in plastic (EasyFlow 120 - I have it available) (cutting the chin part and using velcro, it fits my head.)

My model is depicted below


Problems with process 1:
- I did discover bitterly that hard materials doesn't combine with plaster. I tried anyway to make negative molds 4 times. First try, I forgot mold release agent and have to rebuild a broken part of the cowl; second try went wrong because the depression in temple area worked as a lock; third attempt, mold broke (thin layer of plaster) and fourth one was so-so, but is workable. Had to work the seams (HATE seams). But my plaster negative was damp, and latex didn't cure properly.
Questions: Was moisture which prevent the latex from curing? is there a easy way to make a plaster mold from this fiberglass model avoiding seams????

Below are photos of second attempt, which was wrong because it was trapped


Questions about process 2:
- How to divide my cowl to make a silicone negative? Is there the need to divide it or I could make a one part negative mold?
- How many pulls a silicone mold can handle?

Thanks and best regards, people!

 

[Ozymandius]

It would help if we knew what kind of plaster you were using, but regardless it should be dry and fully cured before trying to cast anything. If there's water in the plaster then it can't absorb the moisture from the latex, which is what makes it cure.

And no, there is no easy way to make a plaster mold that would avoid seams.

As for the silicone mold... I do one part molds all the time for helmets and such but the mother mold does need to be in two parts. And any decent silicone will get you about 50 pulls or so in urethane, probably less in fiberglass.

 

[regisaugusto]

It would help if we knew what kind of plaster you were using, but regardless it should be dry and fully cured before trying to cast anything. If there's water in the plaster then it can't absorb the moisture from the latex, which is what makes it cure.

And no, there is no easy way to make a plaster mold that would avoid seams.

As for the silicone mold... I do one part molds all the time for helmets and such but the mother mold does need to be in two parts. And any decent silicone will get you about 50 pulls or so in urethane, probably less in fiberglass.

Thank you so much!!! That's clarified these questions for me!!!!