Difference in blueing techniques; now and yesterday; thank you.

[YeshuaIsa53]

Can someone explain the difference in the blueing techniques or processes used today as opposed to the "good old days" on Smith & Wessons?

 

[Bullseye Smith]

Someone can get into it more than me. The old blue was done in oven's and the new is in tanks.

 

[john traveler]

BE Smith is correct. The old-style oven blue was done by heating up polished frames, barrels, cranes, and cylinders hung on racks in carefully temperature controlled ovens. Many consider this classic heat-bluing to produce the most beautiful BLUE finishes, used since the beginning of S&W and Colt and most other makers. Other makers used the slow rust bluing for the larger long arms. Since the early 1930s, hot tank bluing or "nitre" bluing has taken over the industry. It was first used for prepping metal parts for painting in the auto industry, but gravitated to military production, usually combined with sandblasting, as seen on Victory models, under trade names like DuLite. It is actually black oxide process, unlike the oven heat that gave a blue-black. Caustic hot tank bluing (black oxide) uses a supersaturated solution of lye to hold the nitrate solution that does the blackening. It actually etches the steel surface, making it possible to produce an acceptable blue without the traditional bright polish on the more expensive guns. Hot tank bluing became the standard for bluing for cost/time reasons.

 

[shovelwrench]

The one big thing that changed is the mercury in the "old" blues. THIS is what made for the real deep blue color of the older blues. It was, and is black oxide.

It's environmental laws that cut the mercury out of our new blued stuff.

 

[WR Moore]

There's also a difference in the degree of polish performed prior to bluing. I've got an older model 28 with the bright blue. Looks nothing like later production of the same model. Once upon a time, it took years to work your way up to polishing the better grade guns.

I thought only Colt did the oil & heat blues. I'd have to find a heat treating chart to see when that might have been discontinued. I do recall that getting the blue color took 500 degrees.

 

[shovelwrench]

There's also a difference in the degree of polish performed prior to bluing.

+1

Its takes high polished steele to yeild high polish blueing, regardless of the type of blueing (or plating)

 

[Kevin Gibson]

The old style is called Carbona Bluing. "Nitre" bluing is a very different process that gives you colors from straw to bright blue; often refered to as fire blue.

The Victory Models were Parkerized, not blued.

Current process is hot bluing, which is done in tanks.

 

[handejector]

To elaborate a little further-
Carbona bluing is not simply a heat process.
The ovens are heated, PRESSURIZED, and the atmosphere is a CARBON-rich (hence the name Carbona) environment via various forms of charcoal.
In effect, you could say the gun is "plated" with carbon via heat and pressure.

You can see a pic of the ovens in <u>Smith & Wesson, Images of America</u> by Jinks and Krein.

 

[2152hq]

Going back even further, before Carbonia Blueing (sometimes called 'machine blueing'),,the process used was 'charcoal blueing'.

This was primarily used before WW1. Very labor intensive as the parts were handled one by one in and out of a charcoal fire as they were heated. A coating of oxide formed, then the part was rubbed down while hot with different substances depending on the manufacturer. Animal oils (whale oil said to be a favorite), powdered lime, wax, etc scrubbed on with burlap or tow were the most commonly used ones.

Techniques varied as did the times in the coals, the number of coats, etc. Each coating built up a fine blueing, The rub downs added to the gloss, eveness of the finish, as well as removing any unwanted scale from the surface..

I know a couple of people that actually still do this type of finish and reproduce it well. I've tried it out and gotten some decent results on smaller parts but when going about doing a larger frame and all the associated parts with it, it becomes a bit overwhelming to say the least. Quickly & efficiently rubbing down parts that are 700F with a wad of burlap dipped in powdered lime is dicey if not dangerous business. I'll try to stick to some small parts if I ever go there again!

Most all long gun barrels were rust blued,,the only production long gun barrel that I can think of that I believe was originally charcoal blued was the Henry Rifle,,there may be others. I've seen some handmade muzzle loader rifles with original charcoal blued barrels.

Nitre blueing was used primarily on small parts, screws, pins, etc. because it was fast and easy to do a large amt of parts at one time in a Nitre Bath.

Usually melted Sodium Nitrate salts, sometimes with other small amts of chemicles added to bring out a supposed better color. Magnesuim Dioxide(?) is one mentioned quite often and I think Winchester used it that way. The temp of the melted salts were varied to get the color of the metal,,,or sometimes the color was the result of the desired temp. 'Spring temper blue' is just that becasue it is the temp needed to temper a spring from it's hardened state. It just happens to impart a very nice blue color to the metal. The yellow 'straw' color on Luger small parts and other mostly Euro auto pistols is there because the lower temperature used in the annealing salt bath imparts that particular color.

Though Sodium Nitrate is the old standard Nitre Blueing salt,,I have used Ammonium Nitrate with success. Temper blueing of larger parts like pistol barrels, frames and cylinders used to be done in such common substances as fine sand by some companys.

Correct temperature,, complete blocking of atmosphere (oxygen) from the part, clean high polished surfaces and correct time in the mixture will get a nice finish.
The same rules applied to Carbonia bluing.

Nitre, Carbonia, Charcoal blueing must all be considered a form of annealing as the parts are heated to ranges of 600F to 800F and for extended periods of time in the case of the latter two processes. Then left to cool slowly on their own. Classic annealing processes but depending on the original steel & heatreat involved, it's difficult to say how the strength of each piece is effected..

It obviously work out OK, but the factorys quicky took to hot salt blueing in the late 1930's when it became viable. Quicker though some operations still used the Carbonia set up well after that. Post WW2 labor costs, mass production and loss of the earlier skilled labor pretty much began the shut down of all the older finishing processes from the classic polishing to bluing techniques.
The European gun industry started using hot blueing salts it a little earlier though still hung on to the old methods, as would be expected I guess.

 

[YeshuaIsa53]

I want to personally take the time to thank each and every person who took of their time to answer my question regarding this. I will print the answers tomorrow so I can have them for reference.
Thank you.

 

[NT430]

Just to add a note regarding the use of "bones". My Great Grandmother and her siblings would gather buffalo bones from the grasslands in North Dakota in their wagon. They'd take them to Park River in Walsh County. The family has pictures of the buffalo bones piled 15' high for 100-200 yards alongside the tracks outside the station. They were told the bones would be picked up and hauled "back east" for medicine and for use in making steel & for bluing.
For years later on our ranch, the "Lazy SS" Hereford Ranch, we would hunt for and find arrow heads and tomahawk club rocks in the same area.