doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Fireblueing How is it Done?

I recall someone here taking the part and dipping in linseed oil, then heating. Anyone recall that?

the oil is used as the quench, the part must be degreased to get an even color before the heat is applied.

Wallace Gusler in "Gunsmith of Williamsburg" used that method. I mentioned it a few times. The video is now available on DVD. http://www.amazon.com/The-Gunsmith-Williamsburg-Colonial/dp/B00282GZPW Good stuff. He builds a gun from raw materials.

Pete

Thanks to all for all the information. I'm getting the impression that fireblueing and straw blueing, ala early Luger parts, are highly related especially when you use the linseed oil/oven approach. Apparently the major difference is the amount of time and temperature required?
Jim

this chart will help

http://www.zianet.com/ebear/metal/heattreat4.html#color

Stump remover is the same thing for nitre bluing. Buying from Brownell's you have to buy a certain amount and pay for the shipping.
Walmart, Lowe's carries the stump remover. You just need a thermometer that goes to 1000 deg, and a heat source to get it there. The salts will liquify and become clear. My problem was that I could not get the temperature hot enough.

I think if you look at SKB's link, that 600* temp is in the ballpark to form the brighter blue color.

The ingredient used in Brownells nitre blue or stump remover is potassium nitrate, also known as saltpeter. The stump remover isn't a real pure form, but it can be used. The melting point is 633.2 degrees F and it becomes a clear liquid when melted. Small parts and screws can be submerged in the molten bath to blue them. This is usually done by suspending them in the bath on a wire. As I recall, the parts are quickly quenched in water when they turn blue. It isn't the most durable blue there is, and it is fairly translucent, but it is attractive for certain small parts.

The process requires caution because molten saltpeter at over 600 degrees can cause some nasty burns. Also, it solidifies into a solid block upon cooling. Then when you heat it again to reuse it, the bottom will melt first, and it can erupt through the still hard surface and spray you with hot molten material. It is recommended to leave a threaded bolt in the bath while cooling, and then unscrew the bolt from the solidified material before reheating in order to have a vent going to the bottom to prevent those nasty eruptions.

Carbona blue was another heat blue process used by Colt, Smith&Wesson, and Luger. The parts were heated over a charcoal fire to around 600 degrees and variously tumbled into bone meal, leather scraps and other organic compounds, or wiped with pine tar oil or fish oil. This process supposedly added carbon to the surface of the steel in addition to coloring it. A high polish was necessary in order to get a rich deep blue. You can Google this to get many other variations on the process.

Even molten lead can be used to color steel. As long as the proper temp can be reached and held for the desired color, it matters little what the substance is.

Though lead isn't a good one to use for higher temps,,either the Brownells salts or any form of sodium nitrate or potassium nitrate will do.

Take them to 850F and the color will be a deep blue/black.
The 650-700F range gives a sapphire blue color, often called 'spring blue' color as it is the color and temp range that springs are tempered at. Which is most likely the real use for the process,,drawing temper.

Carbona blue is a completely different process done in an revolving oven with bone or wood char and in the patented process,,Carbona oil.
True charcoal blueing different again. What they all have in common is that they place the parts to be blued out of contact with the free oxygen of the atmosphere. Some variations of each.

Just heating a part in the air and getting heat change temper colors is just that. But on small parts it does a nice job if you can control it well and is fast and easy.
This is what I'd refer to as 'fire bluing'.

Some English WW2 military parts were 'Blackened' by dipping in oil and burning it off in some manner, perhaps in ovens to control the temp. It gave a fairly decent finish against abrasion, but it's best quality was that it was fast and easy to do I suspect.
I'd guess it or something similar was done in the past too.

fire blue...torch...umm...yes, oh yes...