1915 40AL Sniff Test

[unbeldi]

The brass parts were japanned. Bower Barf cannot be applied to brass as it is a reduced form of iron. In the UK, a different oxide was applied to these brass parts. It was black oxide - a cupric oxide I think.

Jack

It's oxidized steel, not reduced.  It was applied by exposing the part at high temperature to superheated steam in a chamber for some time. This converted the surface layer to various iron oxides.  This needed to be followed by a reduction process with carbon monoxide to revert the higher oxidation states which would give the part a yellow to red tint. The lower oxidation states are gray or black.

Given the time that this all takes, I would say it was expensive to make them that way.

[Jack Ryan]

It's oxidized steel, not reduced.

Thanks, I know it is oxidised and I know how it is done. I accidentally used the wrong word but used the correct word twice further on for the analogous process on brass.

Jack

[zaphod01]

I looked long and hard to find a 40AL I thought was original and correct. This one has the receiver hook painted to match the gray stem and base. The photo makes the hook appear more black than it actually is. The perch and transmitter are black.