Back to Basics 2: Molding Creations,
Positive v. Negative
by KwISt
What a grand time we all had last issue... In our quest for
immortality, we had all our friends over to get Vaselined and plastered.
Now, after the party, we look around and find ourselves with plaster
cast shells (and the facial hair they pulled off with them), and all
the busts we made from them.
Let me repeat the warning to towel the Vaseline off the busts.
Hey, focus! You don't want lingering Vaseline to bubble the
latex, so you may even try to wash the bust down with soap and lots of
water. Stop thinking so dirty!
Positive v. Negative
We're ready to start molding the mask design on the bust using clay...
but this will place a few choices on us. You can take the cheap
and quick route by just building on the positive clay design. Or,
you can do like the pros, and make a negative mold of plaster off the
positive clay design. Let's examine where those choices put us...
I do most of my masks using the quick approach of the positive
bust. I've made many award-winning masks this way, even though it
compromises quality. If you're just going to paint latex eight
layers deep over the bust, then keep in mind that the details and
textures on the clay are going to end up buried eight layers deep.
Negative casts have a qualitative advantage in that they keep the top
surface design details on the mask's top surface. This is done by
making a negative shell cast off the design, so the mask can be filled
from the outside in. Call it "equivalent exchange" if you will,
but the advantage comes at cost. One of those costs is undercuts.
(Think of them as 'curl-unders')
You must decide how to pull off the halves of the negative cast, and it
may not have a linear direction to slide off, unless you make
compromises to the clay design.
A compromised design for negative casting must avoid undercuts... those
turns on horns or other protrusions need be dealt with. Some
designs will split the seam of the shell to ride up the horn's sides,
allowing the halves to easily pull off front and back. A simple
prosthetic like a Klingon forehead may only require a single 'half,'
but it still has to pull off in a consistent direction.
Breaking Away
It's easy to separate the mask off a positive mold. You just
apply layer after layer of latex: slather, dry, repeat! Use
a common paint brush, or you may even smooth the layers on fresh with
your clean hands. With a little practice, you'll see how the
latex fills the wrinkles...
and you may even grow adept at brushing the latex back out of the
wrinkles and details as you layer the latex on. You'll just need
enough layers to support the details and avoid tearing when pulling it
off... six to fourteen typically.
On a negative mold, the rules are different. Instead of 6 to 14
layers required on a positive bust, fewer layers are required in a
negative cast. Casting latex, which has 10 times the ammonia than
facial makeup latex, can be slush cast by pouring out
from a plastic tub, slushing a layer around the shell, and pouring the
excess back into the container. Other kinds of latex, like cold
foam or silicon latex, may get it all in a single layer. (I
personally don't yet have experience in those newer materials.
However, I might learn more before part 3 goes to print, as I just
discovered a source of silicon latex in Michigan that offers an
instructional video.)
The other added difficulty of a pro-style negative cast is that a
full-head mask will require more than one half or shell. You may
also require a 'release compound,' but in a pinch cooking spray would
do. The back of the head and the front would look like undercuts
('curl-unders') relative to each other... they must be pulled out in
opposite directions. At least, that's how the negative cast comes
off. It is conceivable that a slush-cast mask can come out from
two halves sealed neatly together, and that has the advantage that you
can hide the seam better. But you may have to devise a way to
latch the halves together, then reopen them once the last layer of
latex dries.
Coloring
You typically color your latex masks with latex compatible paint.
You can even mix light amounts of acrylic paint into fresh latex liquid
with great results. Just don't paint acrylic directly onto latex
without first mixing latex into it... The result would shed like
leprosy after the first wearing.
If you really need the top-layer details and textures of negative
casting, your first latex layer will need to be the color, and the
lighter colors will be best brushed in first for such an
approach. But if the outer textures aren't as mission-critical
you can brush on the color after the fact, starting with dark layers
inside and ending with the outermost layers of light color.
My final coloring tip is that raw latex is largely clear with a bit
little yellowing when dried. That translucency can make a nice
skinlike property (e.g. I used it in a Grand Nagus mask), which works
great if the coloring just under is a bit rosey or depleated of yellow.
Summing Up
You now have enough info for finishing a cheap-and-dirty mask.
Next issue, I'll examine the impermanent nature of latex, some causes
behind it bubbling or turning to goo, and steps you can take to try
battling that grizzly fate.
Part 1: Make Ridges or
Any Mask
Part 3: Work and Care
with Latex
