I agree with Chris about the need for concentrating the heat- by any reasonable means. By this, I would use thermal bricks, metal shields and coke or charcoal to hold the heat in one place long enough to raise the temperature to a dull red-- and with the borax gone to a glassy liquid.
As he says, his early work was like? Well, might I say old fashioned cinder toffee?
So Steves, this is what you risk and all that careful work is ruined.
In a normal environment, you would be given a bit of thin steel plate, told to clean it thoroughly and put on the liquid borax. Your aim in life was NOT to do something proper but merely to see a puddle of solder appear on the middle of the test piece. Then you would do another piece and perhaps stick a nut onto the sheet. Then you would move to a thicker sheet, bore a hole and put a rod into it-- and watch the solder wick its way through to the other side.
It would be then- and only then that you would be allowed to progress to the real job.
Once it all goes together, it is plain sailing. You then go out- look for a donkey with a missing tail, get the right flux and stick the tail back on.
Well, nearly?
