From: ahahma@utu.fi (Arno Hahma)
Subject: Re: Deep Bluing - How?
Organization: University of Turku
Keywords: blue, chemical, gun, black

In article <9405301534.AA43978@acs7.acs.ucalgary.ca>,
Christopher Lau <clau@acs.ucalgary.ca> wrote:

#What's the best process to get a really deep blue (ie almost black) onto a
#gun part?  On the advice of a gun dealer, I've tried several of the selenium

The best process to get a deep blue is to use a real blueing
process. How deep the finish will be depends much on the
steel, different alloys give very different blues. Mild
steel will become almost black, strongly alloyed steel will
be mostly dark blue and hardened high carbon steel mostly
dark brown or reddish. If the blueing solution is old,
greenish colors may result.

The blueing solution is very simple: 60..70 % NaOH and the
rest NaNO3 (sodium nitrate). This mixture is added to
boiling water until the boiling point of the solution
reaches 140..145 oC. Note, that the total water content of
the solution will be about 40 %, so relatively little water
should be used.

The parts to be blued are immersed in the boiling solution for 5 to 10
minutes (no more or the finish will become reddish). The temperature
must not exceed 150 oC or the parts will immediately become red or
rusty. Below 135 oC the bath won't work either. The parts must also be
free of any grease or other impurities or the finish will be uneven
(spots of different color).

The blueing solution is extremely corrosive to skin and synthetic
fabrics, so watch out not to get it onto yourself (besided, it is very
hot).  It tends to spread itself around (as small droplets or mist)
when it boils, so don't boil it, just keep it hot or boil very gently.
When making the solution, add the ingredients (premixed) carefully, the
solution process generates much heat and accelerates the boiling
strongly. Don't try to blue anything else than iron or steel (copper
might get black, I haven't tried however).  Especially, avoid exposing
aluminum or zinc to the solution, both metals will dissolve very
quickly into the blueing mixture.

#based chemical bluing creams/pastes, but the best I got was a darkening of the
#metal that actually appears brownish in the light.  In addition, the pastes

The low temperature blueing solutions never work well, they tend to
corrode the metal too fast. Then the finish will look like sandblasted
or otherwise rough due to spot corrosion.



ArNO
    2

From: John De Armond
Subject: Re: Chemistry of bluing

David Post  Writes:

#Regarding Hot process blueing:

#Some hot blueing processes are hotter than some silver solder processes used
#to assemble older over/under shot guns.  This means you can damage a gun if
#you don't know about the soldering process used.  I just learned this today.

#Anyone have more details on how to identify the appropriate temperature to
#re-blue a gun with solder work?

The terms are getting mixed up which is causing some confusion.  There
are two major kinds of blueing:  water based and molten salt.  All water-based
blueing, whether the process is "cold" (~room temperature) or "hot"
(~160-180 degrees F) poses no danger to any solder.  As an aside, I'm
not sure of the chemistry involved but the Brownell instructions do
reference a Mil-Spec.

The molten salt process which Dave describes above, also known as Nitro
Blue,  involves a melted mix of sodium and potassium nitrate plus some magic
dust :-)  The temperature range is from about 525 degrees to 650 degrees,
depending on the intensity of blue desired and whether anealing is desired
or not.  Soft solder, ie, tin/lead, is at risk.  Note that silver bearing
(tin/lead with ~5% silver as a hardener) is considered soft solder.
Silver solder (silver/copper/cadmium allowy) melts at low red heat and thus
is at no risk.

As an aside, If you have never seen a properly Nitro-blued firearm, you
have missed a beautiful sight.  Properly done, it is a deep royal blue
that looks a foot thick.  The process control necessary for a
superb job is incredable.  I built a PID temperature control loop for
the  'smith where I moonlight.  We've developed a cleaning and preheating
process that gives consistent results but we have to figure on taking
the while day when we fire up the Nitro-Blue tank.

Nitro-blue chemicals complete with magic stuff is available from
Brownells at the rate of about $40 for 5lbs.  5 lbs will about 3/4
fill a bread baking tin.

John
jgd@dixie.com

From: ohk@nta.no (Ole-Hjalmar Kristensen TF.DT/DELAB)
Subject: Re: Deep Bluing - How?
Organization: Norwegian Telecom Research
Keywords: blue, chemical, gun, black

In article <94May31.234452eet_dst.167014-2@utu.fi>, ahahma@utu.fi (Arno Hahma) writes:
|> In article <9405301534.AA43978@acs7.acs.ucalgary.ca>,
|> Christopher Lau <clau@acs.ucalgary.ca> wrote:
|>
|> #What's the best process to get a really deep blue (ie almost black) onto a
|> #gun part?  On the advice of a gun dealer, I've tried several of the selenium
|>

< Good info on hot bluing deleted>

|>
|> ArNO
|>     2
|>

I just want to add that the oxide layer get harder and more duarble for
some time after you have finished the boiling, so after you have
finished bluing and rinsing, put some oil on the blued parts and let it
stand for a few days. Then you can polish it slightly with 000 steel
wool if you like.

From: gmk@falstaff.MAE.CWRU.EDU (Geoff Kotzar)
Subject: Re: T/C New Englander Kit
Organization: Case Western Reserve University

In article <46759@mimsy.umd.edu> MEDELMA@cms.cc.wayne.edu (Michael Edelman)
writes:
#In article <46737@mimsy.umd.edu> brian@53iss6.waterloo.NCR.COM
#(Brian W. Gamble) writes:

      (deleted)
##I have yet to find a cold barrel finish that will last. I've stripped the last
##attempt and left the steel in its natural state as I don't hunt with it.
##Anybody else got words of wisdom on this topic?

(material about blueing deleted)

#As the T/C arms aren't really exact replicas of old guns bluing is OK,
#but browning is much better. I think Brownell's does a browning solution and
#that's certainly worth checking out.

Brownell carries a number of browning solutions: Pilkington, Mark Lee, and
Laurel Mountain Forge. This last one is the one that I have used. It is a
barrel brown and degreaser. One of the problems with most blueing and browning
solutions is that you must completely degrease the parts first and once that
is done you can never handle them with your bare hands until the job is
completed. The Laurel Mountain formula allows you to do a simple degreasing
operation and then you can still handle the parts normally, no gloves required.
I took them at their word and had no problems with the solution taking. Their
instructions indicate two different types of browning available. If your
tastes run toward a "gentleman's" fine surface they recommend a 3 hour cycle
while if you prefer a more rustic coarser surface you can use a 12 hour cycle.
I have used the latter method on my guns and only 3 applications were required.
The nice thing about this method is that I could coat the barrel before
leaving for work and have a nice coat of rust when I got home. After carding,
it simply sat until the next morning when the procedure was repeated.

#If you're into original methods and have lots of time, you can use the
#original cold rust bluing and browning methods. For browning, set up a
#"rusting chamber"- a box kept warm and humid. Doesn't have to be air tight.
#Some polyethelene and a lightbulb should do. Throughly degrease the part,
#plug the barrel and place in the chamber until a thin coat of rust covers
#the part(s). Remove and card the rust off with steel wool. Repeat for a
#week or two.

On of the other problems with browning in the winter is that the humidity is
too darned low to get a nice even coat of rust, at least here in the north.
A browning box works wonderfully but it just is too much trouble unless you
have a number of guns to do. BTW, if you do order your supplies from Brownell's
get the reprint they offer of the John Bivin's article from the Mar/Apr 1977
issue of Rifle. The part number is 084-081-000 and the cost is $.50. It has a
set of plans for a browning box and an excellent discussion of the various
surface treatments/finishes (browning and blueing) available for firearms.

One way to get around the low humidity problem is to use the browning box that
came with your dwelling: your bathroom. This will require the cooperation of
your family members of course. If you fill the tub with hot water and run the
shower for a short period to bring the overall humidity up and then hang your
parts over the tub you will get a nice even coating of rust. Two things to
remember, the humidity should not be so high that you get water condensing
on your metal parts and keep the door closed because drafts seem to affect
how the browning takes. The only drawback to this method is that you do not
have real control over the temperature and humidity level, this is where the
browning box is much better: you can reproduce your rusting conditions from
day to day and season to season. The other area of your house that works
reasonably well is your laundry room, but in my case the rusting proceeded
more slowly and I had too many drafts making the rusting somewhat uneven.

#Cold rust bluing adds one more step- boiling the rusty parts to convert
#the oxide to another compound.
#                        --mike    medelma@cms.cc.wayne.edu


geoff kotzar                gmk@falstaff.mae.cwru.edu