Products used in this How To:
Pressure Casting Clear
How To will help you understand the process of Pressure Casting.
We have chosen to work with the Alumilite Clear to demonstrate
the difference between a casting that has been pressure cast
and one that hasn't.
are the items we used to mix and pressure the Clear: Pressure Pot,
shop air, Alumilite Clear, Alumilite's Gram Scale, a 6 oz mixing
cup, two 1 oz cups, and a stir stick.
Alumilite Clear using a mix ratio of 1:1 by weight. It will not
cure properly if you mix it by volume.
measured properly, mix thoroughly. The open time is approximately
5-6 minutes. Be sure to scrape the sides and the bottom of the
container. It is very important to make sure you get the mixed
resin into the pressure pot and to apply the air pressure prior
to the resin starting to gel.
our demonstration we will pour the mixed Clear into two 1 oz cups.
The bubbles are many but very small. They are hard to see in this
picture. They do show up better once the material has cured.
we are placing one of the cups in the Pressure Pot to be pressure
is very important to fasten all of the knobs down tightly to the
lid. The red knob you see is a shut off valve which allows us to
hold the pressure within the tank while disconnecting the air source
after it has reached the proper air pressure in the tank. That
valve does not come with the Pressure Pot. The regulator, safety
release valve, and guage do come standard.
putting air pressure on the tank make sure to back the regulator
all the way off. Then connect the air and adjust the regulator
to allow the tank to fill up with 35-40 psi. The tank is rated
to 50 psi and should never run over that air pressure. Alumilite's
Pressure Pots have an automatic safety release valve on the top
of the tank in case the regulator was accidently set allowing the
pressure to release before the pressure builds too high in the
tank to potentially cause damage.
let the material set for 45 minutes before releasing the air pressure
and removing it from the Pressure Pot. The size and mass of a one
ounce cup will cure faster than a thin walled piece allowing us
to demold it faster. We first disconnect the air source, release
the air pressure from the pot, and then remove the knobs around
the lid. You only need to make sure to pressurize the casting until
you know it has hardened up. The concept behind pressure casting
is to crush the bubbles to a point that we would not see them and
then hold the bubbles in that state until the resin sets up. Once
the resin sets up and hardens the bubbles will not be able to expand
back to their original shape and size and will never be noticed
in your finished casting.
remove our Alumilite Clear cup from the Pressure Pot and see no
air bubbles in the poured cup at all.
you can see the difference between the castings on the left that
has been pressure cast compared to the cup that was just mixed
and poured without the use of pressure. The cup that was pressure
cast does not have any air bubbles. The cup that was not pressure
cast has hundreds of small champagne sized bubbles throughout the