Casting Investment Inclusions and Causes

Hey Dan, Actually, I hadn’t seen your earlier posts as I had
accidentally deleted a couple of my digests :frowning: Kinda jumped in on this
at the end…

I have learned a WHOLE lot about investment problems since moving to
the ultra-humid Washington DC Metro area, and picked up a casting
great tip from a chemist/caster friend in Australia who lives in the
tropics there.

I am vacuum packing pre-weighed amounts of very fresh investment
(Contenti Orovest, ever more than 10 days old from the date of
manufacture) using a Tilia Foodsaver home vacuum packing system. I
open the vacuum sealed bags just as I am about to begin my mix. This
puts a “damper” on the hydroscopic nature of the material, and ensures
the material is as fresh and as dry as the day it arrived when opened.

Often, investment that has been warehoused by distributors for
unknown amounts of time can pick up a lot of moisture from the
atmosphere, and if introduced to a humid climate, begins to absorb
even more, breaking down the ultracal to hydrocal. This will affect
the set time of the material and GREATLY affect mold strength, as well
as causing other problems such as water streaks, bubbles, flashing,
and blowouts.

Though impractical for the large manufacturer, this is a great trick
for the small to medium size caster, or someone who only casts every
so often. For very small use, the 1 lb. foil packs of Kerr Satin Cast
20 are great, but pricey…

For larger volume users, I recommend ordering smaller amounts of very
fresh material on an as needed basis. Though costlier, the savings in
reduced problems will more than offset it. Having a truckload of
plaster that you saved a few dollars a barrel on go bad on you will
cost you a whole lot more in the long run…

Also, be sure your investing area is climate controlled, to eliminate
variables in atmospheric humidity which also can affect set time…

Happy investing!

Mark Moretti
Fredericksburg, VA