Ray, Jack, and others that may have done this before. How do you "fire blue" screws like on the old colts? What might have been some traditional methods and what might be some modern?
Thanks for listening
Take care
smallfry

To add to this question... I know you can use niter salts... but what might be the difference in niter salts and blue temp chips you get when cutting heavy on a lathe?
Thanks
smallfry

smallfry---

The bright "electric" blue is caused by oxidation at high temperature.

It's done by soaking the degreased and DRY parts in molten salt peter. It's called "nitre blue".

It's the same thing as you see on lathe swarf but is tougher, deeper, and much more predictable. The nitre has a LOT of oxygen in it.....that's where black powder gets the oxygen to burn.

Potassium Nitrate KNO3. Melts around 635F

[ 11-30-2002, 21:20: Message edited by: Roger Rothschild ]