Steve, Ordinary talcum powder in drugstores contains perfumes
and possibly other ingredients that eventually attack natural
rubber. Over time they will degrade your molds. Done properly, you
should easily achieve well over 90% successful injections. To
start, install a dessicator/filter (drier/oil separator) in your
air line close to the injector - you want clean dry air. If you
don’t have one, get a good dial thermometer for the tube hole in
the injector’s cover. Next clean out your injector and replace
the wax with fresh material. Never reuse wax that drips from the
nozzle or from unsuccessful injections.
There are three variables that must be controlled in order to
get consistently predictable results. Wax temperature, injection
pressure and clamping force on the mold. These three values
should be as low as possible depending on the type of product
(filigree, heavy cross sections etc.). While most people can
adequately control the temperature and injection pressure, they
fail because we cannot accurately and repeatably control the
clamping force between our fingers.
Rio Grande and Gesswein carry a tool called “Speed Clamp” that
utilizes the air supplied to the wax injector to feed a pneumatic
cylinder that applies a controllable and repeatable pressure to
the mold. It comes with its own gauge and regulator so that the
pressure on the mold is regulated independently of the injector.
Once the proper values are found for each mold, write them on the
mold. Any one can then exactly duplicate the original parameters.
If you need further help, Liz Brehmer at Rio Grande or Elaine
Corwin at Gesswein are extremely knowledgeable and will gladly