Team ‘is it magma?’ are ready and prepped. Not really knowing what to expect we wore fully PPE (Personal Protective Equipment) to handle the black molten material.
Before we took the crucible out of the furnace, I took a quick reading on the pyrometer to certify that the basalt was at peak temperature. I recorded a reading of 1250 degree Celsius and waved to the rest of foundry team to go ahead with the pour. As I have had the privilege of working with these people before, the movement of carrying a hot object from one location to another has formed a sort of dance between us. With molten metal it is important to be reasonably swift with your dance, as waiting around allows the molten material to start cooling. Frustratingly due to the nature of rock being an insulator this factor is even more important. At one of the pours, I record the temperature dropping 400 degrees in 20 seconds! Not only did we need to be fast but also the molten rock had a high viscosity… much higher than I had originally thought. It was like a chewy ketchup, which I would expect from other volcanic rock such as ryholite but not from basalt. To counteract this unexpected problem we used a oxy-propane torch on the slow moving rock, to encourage its movement and reduce the rapid loss of heat.
This enabled us to pour a mould but we all understood that it didn’t look likely the the lava had flowed to fill the void. It was just to viscous and thick.
We reloaded the kiln and after waiting another couple of hours tried again. This time, preparing an even smoother foundry dance but still we faced the same problem. Very slow. Very thick.
Third time around I took the crucible out of the equation, a practice which is common in African foundries, and packed three different moulds. One ceramic shell mold with basalt dust, another ceramic shell with already melted and then cooled basalt and one ludo mould and placed them directly into the furnace. This experiment also had its problems, the ludo mould could not withstand the heat and broke forming an ugly mess of brick, plaster and melted glass and basalt. The ceramic shells did better and survived the heat but the basalt adhered itself to the surface so I am uncertain if I will be able to get the forms out of the mould without destroying the whole object.
The results of this first pour were not as expected. There are many questions to be explored but probably the most important question is to certify the chemical composition of the Radstock basalt. Basalt is known to be much less viscous than what we were working with which begs the question.. Is it Basalt?
