This is a picture of gold casting grain and an old wedding band that we are about to melt down with the hydrogen torch. We always have to mix in a little casting grain with old gold because it is perfectly clean and new gold. This helps the whole batch of gold slide into the investment much easier.
Now we have had the torch on the gold for about 30 seconds and you can see that the gold is starting to melt. During this time we are sprinkling boric powder to help clean the gold just in case there is any foreign material on the gold or in the melting dish. While this is going on we are turning the vacuum on and getting ready to take the flask out of the oven.
The picture on the left is the outside of the oven. The instrument panel at the bottom of the oven reads the temperature, which is at about of 1000 degrees. The picture on the right is the inside of the oven. You can kind of see the coils are a red color and that is usually what color everything is inside the oven but the flashe bleached the red out. The cylinders are the flasks with the investment in them. They are placed in the oven with the hole down so that the wax can be burned out and an open cavity is left for the gold to go through.
When the gold becomes melted completely into a pool of gold, like the shiny liquid oval shape glob in the picture, then it is ready to poor. The flask comes straight out of the oven and is put right onto the vacuum. That is what has happened in this picture, then the gold is poured right into the flask before it cools down. The holes you see in the investment in the center of the flask are the openings that the wax burned out of and the gold will go into, which will lead to the item to be casted.
After the gold has been poured in, it is vacuumed into the flask and fills in all voids in the investment. You always want to make sure you have extra gold and that is what is sitting in the center of the flask. Once the top starts to cool, by turning a dull color, then the flask is dropped into a bucket of water. When the flask hits the water, the investment starts exploding out of the tube because of the shock of it cooling so fast. Then you are able to pull out the item that you have casted into gold.
The piece that is pulled out of the water looks exactly like what is pictured. The metal always looks dull like this until we do the polishing and the finishing touches.