Blue gun barrels

[Dennis Glazener]

In the 2013 reprint of "The Gunsmith's Manual" (originally published in 1883) on page 252 "To Blue Gunbarrels--A very pretty bluish color may be imparted to gun barrels by dressing them off to brightness with fine emery paper, and then rubbing them over quickly with nitric acid. When the desired color has appeared, wash them off with clean water, rub dry with a soft cloth, and then rub with linseed oil to prevent any further action of the acid"

Anyone ever tried this and if so how was the result?
Dennis

[Dphariss]

I guess we would first have to know this gunsmith's definition of "Nitric Acid"
If I use the nitric I have straight from the jug there will be a lot of smoke and then erosion and pitting.
I sometimes wonder if this stuff is not put in instructions to cause people to give up in disgust.
I suggest you find a copy of Angier's book on Bluing and Browning.
Solutions with significant ratios of Nitric do tend to turn the steel blue. But unless very weak repeated applications remove the previous color.
So with putting a Nitric based rust blue solution on it must be well depeleted and it must be put on, the first coat, so that the steel is uniformly wet, the stuff has pretty high surface tension, the spots that don't wet properly have to be rubbed with the applicator/rag. If not the spots will never really match the rest of the color. Once into the process extra rubbing will remove the previous oxide layer. Adding another coat will cause a blue cast until it starts to rust again then its brown until boiled. Most cold blues contain nitric and other chemicals.

Dan

[Sawatis]

I've used the old Niedner rust blue method...its basically ferric nitrate with a little HCl thrown in... I can send you the recipe and process I used if you want...I'll see if I can post a good color picture...its a nice deep blue...not black like most bluing and has no copper sulphate in it so it doesn't streak and such.  Its a deep oxidation...very scratch resistant and hard to get to rust after its done.  The formula matches that I've seen for early 19th Browning solutions fairly closely...only difference is you boil and card multiple tiles to build up the lustre.
John

[sydney]

Hi John--I too am interested in what process you are using
             I do a fair amount of rust blue but would like to try something
               else on some jobs
                   Thanks   Sydnney

[Dennis Glazener]

I've used the old Niedner rust blue method...its basically ferric nitrate with a little HCl thrown in... I can send you the recipe and process I used if you want...I'll see if I can post a good color picture...its a nice deep blue...not black like most bluing and has no copper sulphate in it so it doesn't streak and such.  Its a deep oxidation...very scratch resistant and hard to get to rust after its done.  The formula matches that I've seen for early 19th Browning solutions fairly closely...only difference is you boil and card multiple tiles to build up the lustre.
John

Thanks John, I have it and its one of the processes that I am considering. Here it is for others if they are interested http://forums.gunbroker.com/topic.asp?TOPIC_ID=478479

[Rolf]

Here is a link to some rustbluing experiments I've done.
http://americanlongrifles.org/forum/index.php?topic=9755.msg92094#msg92094

Diluting the rusting solution with alcohol is a easy way to lower surface tension and aid even coating.
I'd also like warn against using niter containing solutions on parts with sterling silver accents. Niter pits and discolors silver.

Best regards
Rolf

[Sawatis]

Hi Dennis,
Yup that would be it..it's right out of Dunlap's book which is a great reference if you can get it!  Key thing stressed is degreasing...really gotta do that if you have oil or grease in the bore, under rear sight (yup I pull my front silver blade due to the Nitre like Rolf mentioned!), touch hole liner, or on the breech plug threads...It will reek havoc as it will ooze when you boil it off.  I rub and brush everything out with alcohol or acetone before I start applying the solution.  Good luck getting long fiber cotton! I use strips of old well worn out and laundered terry cloth towel.  Cut strips 2X 6 inches, fold lengthwise and hold the loose ends in a gloved hand...then dip and trail the looped end across the surface evenly...don't let it puddle around the rear sight...I have a dry strip of towel to aid in sucking up any puddling...and the idea is to flow it on ...do not rub!   I like the idea of adding alcohol to the solution...haven't done it as it seemed to have very low surface tension, but i imagine that if you don't cut it back with enough water it will get "thick"...had that happen to some ferric nitrate stain that was a few years old...just puddled on the wood and didn't absorb worth diddle!
You want to get some good carding brushes....very fine  stainless...Brownells carriers a larger one and a small toothbrush one for detail areas...they work great...degrease em in alcohol etc before using em. Thats all I can think of for now!
will try and post some pics tonight...got tied up yesterday...

John

[Scota4570]

Mostly, nitric etches the steel.  On some alloys is does make a nice blue.  I once put diluted nitric on a 1917 Enfield bolt shroud.  It made a perfect looking blue color.  It is still there today, very durable. 

I used to play with express blues quite a lot.  When Anniger wrote his book they did not understand the hazards of many chemicals.   I have an extensive background in chemical safety. 

The birchwood casey plumb brown works as well as anything I ever made myself.  You can boil the part in distilled water to get blue after the BC.  Many of the old solutions contain mecuric chloride.  I can not say loud enough to avoid mecuric chloride.  Stannious chloride will substitute in express blue recipees.  Mecuric chloride is a nuero toxin.  When you swab a solution on hot steel it makes steam.  Invatitabley you inhale some steam. you get a dose of mecury.  BC uses nitric and oxidizers.  Look up the MSDS for an approximate recipee.   

I live in a low humidity area.  Traditional slow blues don't work here.  Sweat boxes area a PITA.  I just use BC for everything, works great.  BTW, gauze pads work well to apply your soluton. 

[bama]

Dennis I use the same nitric that I stain stocks with to color barrels. I coat the barrel pretty much the same way that you do with browning. It will rust brown a barrel very nicely. If I boil the barrel in water after the 1st and 2nd coats the barrel will turn a dark blue/black but I have never achieved a light blue color. Usually after the 1st coat the barrel takes on a light grey blue color but not a finish that I would use as a final finish.

[kutter]

Nitric acid will disolve silver.
The combination of Nitric and Hydrochloric in the correct ratio (3:1 and I don't remember which is which) will dissolve gold.

Both precious metals can be found on firearms as inlays and accents.

But the bluing formula made from the acids and iron filings shouldn't have any free acid in it when you're done making it.
It may have an acidic Ph, but you should have  Iron Nitrate and Iron Chloride

I think the Iron Chloride (Ferric Chloride) content is what is etching the silver parts. Shouldn't be any free nitric in it.

Ferric chloride is used as an etchant for copper (curcuit boards primarily). Silver (sterling ) is 7% copper content,,coin silver 10%. That's what I think the Ferric Chloride is eating away and etching,,the copper content of the silver alloy. Probably would eat away at the copper in brass too.

Any Nitric Acid would disolve the silver completely leaving Silver Nitrate behind while nitrogen gas bubbles away.

FWIW,,that particular slow rust blue solution works very nicely.
Let the reaction complete itself when mixing it up. Keep adding iron/steel bits till the acids won't take and disolve anymore. Then add some more and let it set for a couple days. It may still disolve those.
If so add some more till you get undisolved steel on the bottom.

Pour off the liquid through a simple coffee filter into another jar of convenient size.
The reaction while it makes itself will be smoky w/chlorine gas speuing from it,, and hot,,so wait till all is calmed down. ,,and stand clear of the stuff.
 Waiting doesn't hurt anything.

You can cut the soln w/ distilled water if you want. 50/50  doesn't seem to hurt. Try a few different things w/ small portions so you don't make the entire batch into one new ratio.

It's mearly a rusting soln for steel. Temp and humidity effect the results like all of them.
When everythings working right, it gives a beautiful blue color. It can be aggressive though with high humidity so keep a watch on the parts. 

Keep it out of the bore, but I never plug them while rust bluing.
I sometimes coat them with common shellac. Always when damascus finishing due to the etching necessary.

Several trips through the bore with a shellac wet patch so it gets a heavy coating. It surprisingly holds up to the boiling water trips thru the tank.
I recoat after 5 or 6 cylcle just to make me feel better, but I don't really know if I have to,,I don't want to find out the hard way though.

Wipe any exess off the breech and muzzle ends with an acetone soaked patch.
Remove the coating when done w/ laq-thinner on patches. Even then it takes a bit of work to get the stuff out,,but no damamge to the steel under neath.

* Heed Scota4570's advice and stay way clear of any chemical compounds w/mercury in them.
Yes they work well in the rust blue biz,,but you will not in later life. I know all too well.

[bgf]

Dennis,
I am confused (which seems to be my perpetual state -- what you describe seems more like a "cold blue" than anything else.  Various cold blues do use fairly weak acids in conjunction with other compounds to darken the metal, although I admit I payed more attention to my lab partner (a cheerleader) in Chemistry than to the actual lessons.  Maybe Long John or some other chemistry wizard will explain the mechanism.  I suspect the Nitric would need to be either mostly depleted with something or diluted before it would be safe to use as described, but I suspect also that there is some important information hinted at in the material you quote. 

Dan has a good point also.  The concentration of Nitric acid that is common these days is unlikely to be the same as taken for granted in the past.

[Rolf]

Kutter, Nieder blue contain iron nitrates which turn sterling silver brown by depositing iron compounds on it .  Ferric chloride, sulfuric acid and other acids leach copper out sterling silver.
This is how pickling baths for silver work.

When you hard solder sterling  silver, it turns black because of copperoxcide. The acids in the pickling bath dissolve away the copper oxide. When doing silver filigree work, I used to depletion gild silver by boiling it in sulfuric acid. This removed the copper and left a thin layer of pure white silver on the outside that made the solder seams invisible. Nitric acid on the other dissolves the silver and gives a pitted surface. 





Best regards
Rolf

[wilkie]

Brownells dicropan im bluing used a a cold rust bluing solution.  Polish, degrease, apply im bluing solution (no boiling water), let stand for a day or two, card off, recoat.  About 4 or 6 coats should be enough.  Can be re blued for a touch up if scratched by degreasing and applying another coat.  Give a black oxide coating.  Try it, you might like it.

[Chris Treichel]

I remember a few years ago Robert Wilkinson (from that sword making family) posting somthing along these lines from a book his family published.  Here is the link to the post on sword blueing which earned them a medal from the royal family in 1851. 
The use of diluted nitric acid is mentioned to get the metal white to then use mercury for gold plating and charcoal heat blueing

http://www.swordforum.com/forums/showthread.php?100679-British-Sword-making-and-Etching-1840&highlight=blue

[Sawatis]

But the bluing formula made from the acids and iron filings shouldn't have any free acid in it when you're done making it.
It may have an acidic Ph, but you should have  Iron Nitrate and Iron Chloride

I think the Iron Chloride (Ferric Chloride) content is what is etching the silver parts. Shouldn't be any free nitric in it.

Yup..that makes sense...never gave it a though...but the chemistry is coming back to me
John

[T*O*F]

Dennis,
Here is an old Iver Johnson shotgun I blued using Dicropan IM.  It is a one tank hot blue method but can be used as a cold blue slightly different than the method mentioned by wilkie.

The barrel is polished and degreased and then only handled with rubber gloves.  A small amount of Dicropan is poured into a container.  4/0 steel wool is cut into postage stamp squares.  You dip on into the solution and rub it on a small area of the gun until it is depleted.  Then the pad is reformed to expose new fibers and repeated.  You will get about 3 uses per pad.  You continue until the whole barrel is blued, then wash it down and dry it and repeat the process.  This particular barrel took the solution well and only required 3 complete applications.  After the last application, the barrel is coated with grease and hung to age for a week or so.  This is a very durable finish and will not rub off with steel wool once it's applied.

[Rolf]

But the bluing formula made from the acids and iron filings shouldn't have any free acid in it when you're done making it.
It may have an acidic Ph, but you should have  Iron Nitrate and Iron Chloride

I think the Iron Chloride (Ferric Chloride) content is what is etching the silver parts. Shouldn't be any free nitric in it.

Yup..that makes sense...never gave it a though...but the chemistry is coming back to me
John

Silver and chloride makes the salt silverchloride which is almost insoluble in water, which is why the chloride ions stay in the solution with the ferric ions.  Silvernitrate is very water soluble, therefore nitrates pull silver ions out of the metal and causes pitting on sterling silver.
Chloride ions react with copper and pull it out of sterling and into solution. But since sterling contains only max 5% copper, this gives no visible pitting. Its all about solubility of metal salts and portions of metals in the solid alloys. When the nitrates pair up with the silver ions, the leftover ferric ions go looking for partners and end up deposited on the sterling silver as a ugly brown coat that can only be removed by sanding.

Best regards
Rolf