Re: Investment Mold Dewaxing and Firing


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Posted by ruth on July 11, 19100 at 04:34:43:

In Reply to: Investment Mold Dewaxing and Firing posted by David Conway on July 09, 19100 at 21:37:43:

NB we make plaster and grog moulds.

1. we dewax and fire the mould at the same time because we burn our moulds out in a kiln. we do not have the facility to recycle the wax and its probabaly worth noting that this method creates a bit of smoke (we are based in an art college with good extraction). We use an electric kiln. we put the moulds in when they are dry but I know some people think wet reduces flashing (i just havent had a chance to try it yet). the moulds can be piled on top of each other as long as they are stable. cups down so the wax can drain out.

all temerature are degrees C.

The program we use is as follows...

45 degrees C per hour to 600 degrees

5 degrees an hour until 650 degrees

hold at that temperature for 24 hours

slow drop to 200 degrees.

This means that the wax is gone completely and the water (real and chemically bound) is gone too. Its really important you get rid of all the water or you will have problems.

2. all the glass casting people steam their moulds as it a very clean way of recycling the wax. i should imagine if you dont have extraction it would be well worth investigating as I have been told wax smoke is carcenogenic (that could just be an art school myth though I am not sure). the smoke is certainly a pain anyway! dont forget you would have to fire the mould after steam dewaxing to get rid of the water.

3. we have taken our moulds up to temperature faster but have found they tend to crack a bit more, this programme gives us fairly consistently good results.

4. like i said we use an electric kiln. in theory the water is suposed to damage the elements but ours are still fine (i think that is ceramicists scaremongering).

5. we get the moulds out at about 200 degrees C. wrap them in plaster and jute scrim around the sides and bottom to reinforce them and then put them in the sand pit. i should imagine they are about 150 degrees when we pour.

hope thats helpful and that this gets posted this time - i think i messed up yesterdy.


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