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Investment Procedures

Lots of stuff being said about investment! Like Peter said check the
archives! Good stuff there. A few observations from my casing
experience. Time the gloss off of your investment and work backwards
to make your investing time schedule. End the final vac and pour 1
1/2 to 2 minutes before gloss off. The culprit that causes water
trails is MOVEMENT of the flask before gloss off and after final
pour! Don’t bump, move or stomp on the floor (concrete shop floor
really helps) The agitation of the flask after final pour is what
encourages the water to separate against the wax in the time before
the water is completely drawn into the hardening plaster. So keep the
finish pour-to-gloss off time as short as you can and keep the flask
motionless!! I have experimented with water temps extensively. Warm
or hot water helps a lot. I have not found an appreciable difference
in setup time using very hot tap water. The main benefit to using
warm or hot water has to do with the chemistry or the recipe of the
investment. In the early days (40’s, 50’s & 60’s) it was helpful to
paint your wax with a surfactant (soap) to reduce surface tension and
facilitate the release of air bubbles. The major manufacturers of
investment have added surfactant to the powder so you can skip the
wax painting step. However this is why it is helpful to mix your
investment thoroughly for at least three minutes before your first
vac. Consequently this is also why warm or hot water is better. It is
easier to wash anything with warm or hot water. The combination of
thorough mixing and hot water “wakes up” the surfactant and helps to
break the surface tension. Contrary to urban legend, investment
powder is not radioactive. Keep your shop clean and use a good
respirator. According to OSHA, the major exposure to silica comes at
quench time. If you can afford a water blaster, let your flask go
cold before removing the spent investment. If you must quench, wear a
respirator, dunk quickly and swirl the flask around under water.
Don’t plunge it in and out of the water. Everyone is excited to see
their casting and can forget the safety procedures. That steam
carries fractured silica, the worst kind.,

John, J.A.Henkel Co., Inc. Moldmaking Casting Finishing, Producing
Solutions for Jewelry Artists