fgr

You know, I think it's time we add the strawing process and variations to the frequent question list...


Ted is really one of the resident experts in the field, but he is understandably hesitant to explain his procedure.


I suspect the varnish look that we sometimes see on the parts is simply old oxidized oil.


I believe that I read somewhere that the original parts were air cooled and dunked into sperm oil, the modern equivalent is transmission oil.


Oven heating can work. I have heard of people putting a pan of (clean) sand or shot into an oven with a thermometer to measure the temp. When the is correct for their application, the cleaned and buffed part is "cooked" on/in the shot until the color is reached. One old text I have suggests a stove top heavy iron plate. And Brownelles sells a product, a salt bath, that is specifically for strawing and bluing small parts (along with instructions) called Nitre-Blue. It can be used on a stove top or hot plate.


Obviously the more control you have over the bath temperature, the higher the repeatability will be, so I suspect that it would be very hard to get consistent results with a torch.


But while strawing of a metal is temperature dependent, it is also dependent upon the metal, it's alloys, carbon content, hardness, previous work history, and probably a few dozen other parameters that I am unaware of, so practice seems essential.


There were some excellent posts a while back on strawing and different processes.


hope this helps some...

FGR