The wax carving is set up on a rubber base plate, designed to take a steel sleeve. So now the wax sets inside the sleeve, which is pressed into the base. This places the wax into a hollow cylinder, surrounded by empty space and supported by a wax sprue grafted to the bottom of the item and the center of the base. Then you're ready to mix the casting investment and fill the flask...

Casting investment is mixed and poured into the open top of the metal sleeve, completely surrounding the wax with plaster and entirely filling the cylinder to the very top... ...actually ya can leave just a bit of a drop as you take the flask over to the vaccum table and gently aggitate the mixture to remove any air bubbles in the plaster...

These will show up as casting flaws so it's important to throughly vaccum the mixture to assure the find detail which was rendered isn't ruined by a stupid bubble clinging to the wax... Now we let the flasks set on the rubber bases, the plaster cures & drys. Then we take off the rubber base, exposing the wax sprue/hole in the base end... The ring wax is now completely surrounded by investment/plaster, and it's ready to install in the oven to remove the wax by melting. Important here to keep the temprature higher than the melting point of the wax, but below the boiling point. If you just toss in the oven and crank the heat up the wax will boil and cost you resolution and detail in the casting.

The next stage of the process is to make a visit to the burn out ovens, which are on a computerized four stage 12 hour burn out at Associates for excellent results. The wax has a low melting temprature, so we have the first stage set at just over the melting point but before the "boiling point" of the wax, which will erode the inner surfaces of the plaster and screw up the detail of the casting... After a four hour temprature hold which has melted the wax and caused it to run out of the bottom of the now open ended flask the wax is nearly entirely vaporized and the shape of the wax is ready for the metal to occupy the space... Now the real fun stuff begins :) ...oh yeah, if your room is beginning to fill with choking smoke and smell like "burning tires" you forgot to remove the sprue base when ya tucked the flasks into the burn out oven... Har! :) Remember to remove that base before you stuff that flask into the kiln....

The principle we used the most in the past was based on using centrifical force to "sling" the metal into the flask from the hot crucible in which it is melted completely... Now we've got a wonderful vaccum casting set up that if giving us the best results, and we also cast platinum too in house via a vertical centrifuge... Vaccum casting gives us better detail and a more predictable result by far, without the turbulence of the older broken arm casting methode. More on this change later... Since the wax is now totally evaporated, the space is ready for the metal. This image shows a flask being placed into the casting machine, and the metal in the crucible being melted...

Once the metal is ready, the metal being a fluid as water (without burning the alloy), and after the casting arm is wound against the spring (which will fling the crucible and flask at high speed rotation) the latch is dropped, the arm begins an impressive journey, like a high speed sling it uses the metal's own weight to force the molten mass into the place the wax occupied... ...a breath taking site it is :) Commonly called the "broken arm" casting principle.... ...and for a few moments it spins faster than your hard drive's platter.... ...and it will break yer arm too, if yer not careful :) Vaccum casting is a much gentler process, using the weight and the vaccum to assist complete filling and better results.

We now use vaccum casting, but we still use the "broken arm" casting for very predictable quality results on massive items... We are doing more vaccum casting each day, and are finding this to be very interesting... Update, we now use vaccum casting about 90% of the time, with fantastic results... ...but you can plainly see that, so read on :)