S&W Bluing Methods

[2152hq]

It is confusing at times to read through the old formulas for metal finishes. The terminology used then is different from what is generally understood these days.
Browning was a general term used because the the way to either a brown or a blued surface was through browning(rusting) the metal.

Hot salt blueing was just beginning to be used at the time Angier book was published in the 1930's.
Many of the recipes in the book are from the 19th century and even before. Other than rust blueing at that time, the other ways in general use to get a blued surface on large parts were charcoal blueing (different from carbonia/machine blueing) and a few other types of temper blueing.
Browning, bronzeing, blacking, blueing,,,I'm sure there's more to add.
The term doesn't always indicate the color nor hint at a specific process to attain it.

 

[Oyeboteb]

Far as I know, Steel heated up into the range where 'colors' begin crawling, as was well known to Blacksmiths or related, if quenched or cooled 'there', the colors remain.

If this is done in an Oxidizing ( Oxygen excluding ) Atmosphere, likely the Colors remain a little better or will occur or remain more vivid or are not going to be interfered with by any formation of Oxides.

Mineral or Metallic Salts ( 'Bone', is refractory, and, though made up of compounds, is none the less, essentially compounds of Metals and other elements - Calcium, Mangnesium, Boron, Phosphorus, Manganese, etc, are Metals ) or Organic compounds can contribute to or occasion nuances in a thin or molecular layer in how they may combine Molecularly with the Steel at Heat.

This then would be the pragmatic basis for any Heat related Blueing operation - an Oxidising Atmosphere, a way to controll the rate of rise, the terminal plateau, and then dissipation of the Heat, and, the introduction of whatever Compounds as will molecularly combine with the surface of the Steel to produce new compounds which then occasion premenent nuances in the Color of that Heat, which basic Color will be occuring anyway.

One can obtain a vivid 'Fire Blue' merely by evenly heating a piece of Steel in the open Air and letting it cool...for that matter. But I will guess, that it will not likely be quite as durable as the Blue which is in effect protected by discrete Compounds molecularly bound into the surface of the Steel.

 

[DWalt]

Not S&W, but Ned Schwing's book "Winchester Slide Action Rifles" describes Winchester's metal finishing process in some detail. It applies to slide-action .22s, but the same bluing methods were probably used on all Winchester products. Prior to 1939, Winchester used a rust-bluing process using a solution containing nitric acid and several other chemicals to do the rusting (Shwing provides the names of the chemicals). Rusting occurred in a humidified chamber. Each part went through five rusting and carding cycles. From 1939 onward, Winchester adopted the Du-Lite hot dip solution bluing process, which was simpler, faster, and cheaper. The interesting aspect of the Winchester hot dip method was that it used two successive dips in two bluing chemical tanks (with a rinse between), with the first dip tank being at a slightly lower temperature than the second. It was stated this resulted in a significantly deeper and more uniform bluing appearance. I believe this is the only time I have seen any mention of the double-dip hot bluing method.

 

[shortgun]

American Furnace company

https://tinyurl.com/American-Furnace

Hi. I stumbled onto this site while researching something else. It seemed fascinating. I did find some info on Google Books that explains the process as set down by American furnace.

I have done a little hobby blacksmithing in the past. We get a nice black finish on iron by using a cotton rag and oil on part in the 500-600 f. range. The burning of the cloth and the oil will impart a nice black color. Not as durable though. The other method is using green coal and heat. So the coal tar thing makes sense.
The use of whale oil I think could be substituted for with peanut oil. The flash point of Flash point of whale oil is around 230 °C (446 °F.
Peanut oil Refined 450°F (232°C

The only thing I think in involved in a heat treat with oil (whale oil was supposedly prized for quenching knife blades also.) Would be it's flash point.

Anyway hope this helps in the mystery. Mike

 

[DWalt]

I'd say if anything, that the differences between the suitability of different oils as quenching media is more likely to be related to thermal conductivity rather than flash point - but I don't know. For sure, it would be close to impossible for anyone in the USA today to get their hands on enough sperm oil for quenching.

 

[shortgun]

Yeah you are right. The higher the flash point the more the oil will conduct heat away from the part being quenched. Higher flash point = faster cooling.
When quenching in water a steam jacket will develop around the part. Preventing the part from cooling rapidly.A little swishing is involved to break up the steam jacket.

Commercial heat treaters that do batch parts will use a pump to keep the fluid flowing.
Fast cooling would be important to get the color just right. That and practice.

Very interesting stuff though. The other fact I pulled from a Machinery manual on Carbonia oil is the ratio of carbonia oil to charred bone was 8 quarts bone to 1 pint of carbonia oil, well mixed while warm.

 

[SDH]

Oil is used to temper by burning it off because it burns at very close to 600 degrees, the spring temper temperature. This is an archaic method of drawing the temper. the resulting blue is also quite beautiful and very close to the temper, nitre or heat blue shown in the above photos.

This temper bluing was Not a method used by Smith & Wesson. It is a method I use on a regular basic for screws and other small parts.