From: =?iso-8859-1?Q?Mathieu_Ren=E9?= <creaturiste-AT-primus.ca>
To: <puptcrit-AT-puptcrit.org>
Date: Sat, 27 Sep 2008 01:28:22 -0400
Subject: [Puptcrit] Tip: Melting plastalina


Hi all.

For those who may not know, Plastalina is a pro-quality oil-based clay, 
designed for sculptors.
I love it!
It does not dry out, is easily influenced by heat and cold and solvents, and 
allows for extreme detail work (especially the harder grades), making it a 
must in the special effects, automotive, model making and toy making 
industries. It does not produce dust (unlike potter's clay which contains 
silica, very bad for the lungs)
I use plastalina almost exclusively when designing puppet heads.
The mnore I use it, the better I get at details and surface control.
I,ve grown so accustomed to the grade I have, that now it feels too soft for 
my taste, I crave a harder grade, so that I can still get a smnooth hard 
surface even in the summertime (right now, my soft Chavant NSP is too tacky 
in the summer heat, making it more work to smooth it. The coolness of my 
apartment in the winter makes th same clay perfect to work with.


I still use potter's clays when I need a very quick modeling and smoothing, 
but I make sure I clean up like  a maniac after I'm done.  I've been sick 
for a few months once from the clay's dust, (victim of the lack of proper 
safety information, I did my clay work in my small bedroom as a student!), 
so I don't want to go through that again!

Back on topic:

Yesterday, on the short puppet film contract, we poured some melted 
plastalina into a silicone mold to create a copy of the original we had, so 
we could change the facial expression and re-cast, so the puppet will have 
two interchangeable heads.


Well, the process was straightforward enough. I just put some small chunks 
of plastalina into a pan, and slowly heated it up on the portable heating 
pad, constantly stirring to avoid burning. I wish we had a double boiler, 
for real safety, but we were in a rush, in a well ventilated large studio, 
and I made sure I used as little heat as possible.

Then I poured it into the mold, rotating it to make sure the liquified 
plastalina would go into all the details.
It helped that there was an indication on the mold to tell me where the 
puppet head was facing (the mold parting line was in the back of the head).

I did a few pourings, waiting for each too cool down, hoping to speed-up the 
cooling process, compared to pouring it all at once. Well, it works out that 
it's a bit longer actually, with all the waiting for each step, especially 
since this is increasing the risk of air pockets, which did happen this 
time. I plugged it easily later, but next time I'll  just pour all at once 
and wait patiently. A second pour will be necessary, as the clay contracts a 
lot as it cools.

The first time we poured this clay into this mold, we had a major air bubble 
texture problem all over, but we now know it was because of an excessive 
application of release agent in the silicone mold.  This time we didn't add 
any, and we barely got any air bubbles.  The mold has none.

Melting plastalina is not only good to fill molds ad make copies, it's also 
a good way to make some drippy/organic/hairy/lava-like groovy textures (can 
be dripped or painted on), and to use as an adhesive between parts of the 
sculpt.

I read somewhere that maybe not all plastalinas are good for melting.
The one we used was Chavant NSP (soft).










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