Fire blueing
 

A few evenings ago I decided to see if I could fire blue something. I set a highly polished repro C96 extractor on the orange-hot burner of an electric range and it immediately started turning the desired peacock blue. Took it off after about 20 seconds and let it cool. The blueing was perfect, only it rubbed right off. Is there an easy way to fire blue small parts? KFS

Karl, the technique is straightforward but tricky. First the part must be absolutely squeeky clean. The heat source must be oxygen poor, fuel rich. A charcoal fire with very low air draft or a gas burner with low air and a "smoky" burn or an acetylene torch, same conditions. Heat the piece slowly and keep it at the blue temperature for at least 10 minutes, without overheating (therin lies the tricky part). Low oxy levels cause the blue to form slowly and bind better to the surface. Immeadiately quench in oil when removing from the heat. I suggest highly polished ten penny nails as a learning tool. You do the polishing so you learn two things.

Heinz

And bear in mind that if it's a spring you're working on and you overheat it, it's ruined.