Talking with @graeme the other day inspired me to get the soldering iron out and put together an inductive annealer to take advantage of the excellent case-to-case consistency they are capable of.
A quick play with various coil configurations quickly showed that for heating brass a gapped ferrite used to concentrate the magnetic flux would allow annealing with quite a low input power, and that could be run from a benchtop power supply. Importantly I was able to get away without the need to water cool the induction coil.
I threw it all together on a piece of plywood along with some timing circuitry, so now – similar to the Annealing Made Perfect units - the case is hung in position using a shell holder, and then it all happens with timed precision at the press of a button. :D
First a picture of the workings with a case being overheated for effect. :D:D
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I then ran six cases through, annealing for between 6 seconds and 11 seconds at a set supply voltage, and checked the resulting colour of the brass, and where the induced heating had reached with 450F and 750F tempilaq. One advantage of the inductive method of heating is that tempilaq can be used on the outside of the cases without any risk of burning it off with elevated flame temperatures above that of the brass.
Below, blue 750F ( 400C ) tempilaq.
At 9 seconds the necks just starts to emit in the dark. At 11 seconds the glow is clearly visible in low light conditions.
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Grey 450F ( 230C ) indicating the safety margin towards the case head.
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And three photos for reference showing the colour of the necks with different light angles. Sorry the order of the cases is swapped in a couple of these.
6 seconds: slightly darker gold than the original brass,
7 seconds: deep gold,
8 seconds: pink gold
9 seconds: stainless steel
10 seconds: straw
11 seconds: pink/purple, and colour extends around the shoulder onto the body
Again there is the benefit of knowing that these colours are not influenced by any flame effects.
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