doublegunshop.com - home Forums Thread Like Summary - Heat bluing

On and off, mostly off, I've been playing with heat bluing. I think that I have finally a good way of doing things
and thought I would share it.

I took an inexpensive hot plate and put a half inch thick piece of aluminum on that to distribute the heat and
another block on top of that, to which I attached a thermocouple that came with my $20 digital volt meter.


On top of the block with the thermocouple, I put test pieces, placing a stainless steel travel mug over this
to block air flow.



It took a while to get the temperature stabilized at 295 C, but when I did, I put a skeleton grip cap and screws onto
the block, the screws in the grip cap and the threaded portions dropping into the holes in the block. I ocassionally
lifted the travel mug and observed the changes in the grip cap color. After the last bit of purple had disappeared
and a decent blue was there, I quenched the piece in kerosene. I was very happy with the results. Below is the
grip cap tightened down onto a wooden block. I also made an ebony insert. It looks better in person, than it does in the closeup.



it will go on this project here



I doubt that I am the first person to try this on gun parts, I did find a link to someone using the same method on making
hands for watches via this method. If you are interested in trying this, the link to the color chart below is useful

steel color chart

Nitre bluing is in fact heat coloring. Different temps give different results/colors. The salts do nothing more than maintain uniform heat/temp. A lot of folks temper springs and other steel parts in nitre salts, especially when it comes to “drawing” the steel back after heat treatment, which is especially important when making springs or using hardened mild steel when making a tool.
As was mentioned earlier, molten lead does the same thing.

Quenching in kerosene? That’s ballsy. I would try using something with a bit higher of a flash point (dealing with relatively high temps when coloring with heat, to include hot ignition sources, etc) like a dedicated quenching oil, olive oil, safflower, water, etc.

Looks par-fect to me.

“ A couple of things I'd welcome input on - when doing this with heat is the durability of the finish any different than doing it with nitre salts? Similarly, what is the overall durability of the finish? I realize it polishes off easily. Does the finish bring any additional rust protection? Any input is appreciated.”

The coloring is not durable.

There’s no difference in the colorings durability done with either salts or flame. It’s still coloring done by heat. Salts just heat up and surround the steel in a constant temp bath. Whether you accomplish it by using a flame or salts, all your doing with either method is heating the steel to bring out a particular color whether that be straw/yellow, purple to various shades of blue to black and even gray.

It provides no real rust protection because the coloring doesn’t hold oils like blacking does.

One trade trick when using a flame is to heat the pin or screw from the bottom up. It allows the pin/screw to heat more uniformly. Don’t apply the flame directly to the steel, move the steel in and out of the flame and go slowly.
The higher the polish, the better the color.

The last screw I heat blued was some 20 years ago. It is the top tang screw on the last m/l roundball rifle I built. I browned the barrel/breech/tang, but I wanted to see how a blued screw would look in the tang. It worked perfectly, gave a fairly bright blue, and has held up fine for all these years. No loss of color.

What gauge?

The method that works for me for torch bluing small screws is to use a piece of thin, no thicker than .125, brass, drill holes in the brass stock for the screws to pass through, then heat the brass with the torch. The heat goes through the brass to the screws and the color change happens slower so easier to control. When the desired colored is reached just dip into water to stop the change.

For larger screws I have a small can of chips from the lathe and lay the screws on the chips and heat the can from the bottom.