Blanket blueing?

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I seem to be living in a bubble. Have any of you ever heard of blanket bluing?
When I was an armourer, one of the bluing methods I learned was blanket bluing.
The method
Heat the steel to almost the blue stage. dip wool felt into used engine oil (in the old days of course they didn't have engine oil). The blacker the better. Rub it onto the steel until evenly coated. After cooling, steel wool to remove excess clumps. Progressively finer grade (steel wool is well oiled) until a fine finish. Produces a very fine black coat. Do this outside as the smoke is pretty intense.
That is the short of it. It takes a while to get the right temps and procedures. I used to do a lot of this.
Is this a lost technology? Anybody else ever heard of it or done it? can't find any reference to this old method.
 
It works very well.

I still use it for stock ferrules and bands on milsurps I'm refinishing, mostly Lee types but not always.

Usually, a decent blue works just fine but with used parts, "blackening" gives a better finish that's very durable in the field.

It looks much different than Phosphating and IMHO lasts longer.

As you mentioned, proper temperatures are critical. Too hot or too cold causes all sorts of issues.

It also requires a heat source that will heat the metal uniformly. That's why I limit my endeavors to small parts.
 
I knew I couldn't be the only guy to know this. Blanket bluing may just have been another name. Comes from using wool material.
 
Lots of offshore tooling comes looking like it has this finish. I've never seen the need to use it on a firearm. There are so many better ways that really aren't that hard.

It's a very durable finish and works very well on parts that have a bit of corrosion or are worn thin.

I've never done it to a receiver or barrel, just smaller parts that need to look like the original finish on some older firearms where the process was used.

Some folks insisted "used oil" was needed to get the black. Not true.

Yes, you're right, these days there are better methods available but they don't really achieve the same effect.
 
I learned this method when I was a gun plumber in the RCEME corps. I am sure there are many methods. Wool felt was used with old oil. The felt left a coating that would last forever and you had the option of steel wooling it till you got the finish you wanted. Gave a very black finish. I was told the carbon in the old oil helped the colour. Poorly done, it looked like crap but would still protect the metal. It was as much a coating as it was a finish.
I guess this dates me.
 
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