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How to Seam a Mask


by Vance Hartwell and Neil Goldsmith

  Masks are typically molded in multiple parts.  This means you have two or more mold pieces that are then rejoined for casting.  The goal when creating a multi piece mold is to minimize the gap between the  mold pieces.  It is impossible to eliminate that gap altogether, but you can work at making it as thin as possible.  The seam problem develops where the mold fits together,  A tiny seam is created and liquid latex will leak into that seam.  After you pour the latex and it has dried into the mold, you get what is called flashing along this seam.    This flashing must be removed and the seam must be  repaired to the extent that it is no longer visible or at least as invisible as possible.  The picture to the right shows flashing on a blank pull.  Most of it has been trimmed, but you can see where the 2 mold halves were joined. 
  Vance Hartwell has been in the FX business since the 80's.  He has done it all in a lot of popular shops.  Seaming a mask must be perfect for this level of work.  Even a tiny seam is unacceptable.  Vance shares with us his technique for seaming. 
  What you will need:
  cuticle scissors
  cotton bullet tip for Dremel
  solvent: Bestine or Hexane
  Mask in need of seaming

I first trim as much of the flashing and seam as possible with the scissors.  I trim as close as possible, too, but don’t cut below the surface of the mask.  It’s best to leave the seam “up” as opposed to cutting a trough. 

I then use a Q-Tip and put some of the solvent onto the seam, kind of soaking the latex.  This swells and softens the latex a bit, making it easier to Dremel off.  I then use the cotton bullet to buff off the seam.  You’ll find that going one direction is easier and faster, but leaves the seam kind of “fuzzy”.  Go that way first.  Then go the opposite direction.  This way is a bit more difficult to control, but it leaves a much cleaner seam. 

I then put more of the solvent on with a Q-Tip.  This cleans whatever residue is left.  Just do a few inches at a time and you should have a nearly invisible seam.  You can also “sculpt” in detail across the seam with the Dremel and cotton bullet, too.  Many times you’ll have wrinkles or something that cross your seam.  Just use a bit more pressure and carefully cut these back into the latex.  This will help disguise the seam.

If you have a hole or damaged detail to repair you can do what I do.  Use some V-Thix to thicken some latex.  Make it pretty thick. Now add some Pros-Aide.  I like about a 50/50 mix.  I make the latex thicker than I want because when you add the Pros-Aide it thins it back down.  You want a nice thick paste consistency.  Use this to patch/fill/sculpt any holes/detail/whatever.  The Pros-Aide in the mix makes it stick to the already cured latex and the latex in the mix makes it easy to Dremel.  You can also tint this mix if you’re repairing something that’s already painted.  By doing this you may not have to paint your repairs, if they’re small enough.


  Note: LMC will be posting more about V-Thix which is one of Vance's creations.  It's a much better and safer substitute for Cab-o-sil