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Mike Leahy's Diary

Day 33: Smelting

Mike putting the thermometer into the furnaceBeing TV6, the last programme in the series, most of the tools are broken or missing. Our resources are very low, so old projects are cannibalised for wood, screws, nuts and bolts. Everything we make is designed around the materials available.

The weather is great, just like a British summer day, even so, when we try to light some coal it is too wet to get it going. We are running out of time. Kate and some of the crew help me to spread a tarpaulin on the floor and spread the coal out in the sun to dry. Getting a furnace going isn't as easy as just lighting a fire. The whole of the inside needs to heat up, and that takes time.

I make a thermometer out of a brick and some small pieces of metal. It is based on the principle that different metals melt at different temperatures. Lead melts at about 330oC, aluminium at 660oC, brass at 1027oC, gold at 1062oC and copper at 1083oC. If the copper in my ‘thermometer' melts then the gold in the crucible should also have melted. The other metals indicate how close we are to the temperature that we want. However we have two problems. Firstly the metals that I use are likely to be alloys (mixtures of metals) so the melting temperatures will be different. Secondly we were unable to get the ‘thermometer' into the middle of the furnace. Even so, it will give an indication of the temperatures inside the furnace.

Kate  with bellowsEventually we get some coal to burn in an open fire and drop it into the furnace. On top of the hot coals we mount a grill on which we place the crucible of gold. We then take it in turns to pump the bellows to get the fire burning nice and hot. I didn't expect them to last long, but with the exception of a couple of broken broomstick handles they are OK for the whole day. The only other problem was when a hot piece of coal was sucked into Kate's bellows setting the leather on fire when the reed valve became stuck. This problem is solved by pouring water on the pipe leading from the bellows to the furnace, which cools anything sucked into the bellows before it can reach the leather. After a while we check my ‘thermometer' the results are inconclusive, so J came up with the idea of poking a copper olive (used by plumbers) right down into the furnace next to the gold. Two minutes after putting the olive into the furnace it has melted, leaving only the steel wire to which it had been tied. We now know that we are up to temperature so keep the furnace going until the fuel runs out. As late afternoon develops into dusk the flames shooting out of the furnace chimney look stunning against the snow capped mountains. We know that we were in business.

There is no point burning ourselves trying to retrieve the gold this evening so we leave the furnace to cool naturally.

Back at the huts we were to share our last meal with Ricky. He made a local speciality – whitebait. Here on the west coast whitebait is nearly as valuable as gold. People will fight to the death to defend their own fishing areas because the catch can be so lucrative. We ask what Franz Josef has made of us. Ricky replies, "Better people". I think that he is right.

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Photo: Mike Leahy
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