| Your first thought when you see this is that the | | | | Sand box!! I bet you had already guessed that? |
| plastic mold would melt or catch fire! You are | | | | The plaster pattern is placed in the box and sand |
| right! The way it is done is as follows... | | | | is packed around it. This is special sand that |
| This is going to be a story about a foundry that | | | | cannot be reused. It is mixed in a big machine |
| cast propellers for boats. That is where I learned | | | | with waterglass just before it is to be used. This |
| how plastic molds are used to cast metal. | | | | is packed into place and CO2 it blown over it to |
| I once rented space in a foundry that cast props. | | | | harden it. |
| It was a dark and dusty place. Also very hot | | | | Once this is ready the metal is heated in the |
| some days! Like when the furnace was heating | | | | furnace and then poured into the mold. It is |
| metal. It was a little noisy then to. There are big | | | | allowed to cool 12 hrs or so (this depends on the |
| fans running to feed air into the furnace. | | | | size of the casting - bigger equals longer). Once it |
| Here is how they would use the plastic molds. | | | | has cooled the sand is broken away and |
| First they would cast in plaster, using the plastic | | | | discarded. The casting is cooled for another 12 or |
| mold. Next the plaster casting would be used to | | | | so hours and then ground and polished. |
| make a new mold using sand. This mold is called a | | | | Copyright © 2005 Delmar Germyn. All rights |
| "pattern" and will be used to make the sand mold | | | | reserved. |
| for the metal to be poured into. This is done in a | | | | |