doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Hot bluing and solder joints

Another consideration with hot blued soft soldered barrels, in addition to the salt bath eating the solder away, is that it is pretty hard to keep all of the salt solution out of the void between the barrels, and if and when some of the salt residue gets in, those of us in the northern climates know what the salt on the roads can do to steel/iron. Taking apart a barrel set for relay that has been hot blued shows what the salts due to the barrels inside the ribs over time. Originally barrels were fluxed with rosin as the flux and the rosin is an inert material, and providing no water or bluing salts have gotten in, the soldered are of the barrels look the same as when they were soldered together.
Sometimes a ribs can pop loose, forend loop loosen, and if the barrels have been hot blued, it is difficult to get a good solder joint repair. And the salt residue is still in there.
There are ways to flush the void area to minimize the salt, but it may still have suffered damage.

And squirting oil into the void doesn't stop the rust.

Yes it is true that a lot of modern guns are blacked/blued with hot salts but that doesn't make it right. Silver solder and Braze are unaffected by hot salts but how can you be sure the rib to barrels fit has no holes or even tiny pin hole, hot salts will get in everywhere, many guns have holes in behind the extractor allowing salts right in under the ribs you cannot be sure that all salts are flushed away and it only needs the tiniest amount left behind for the damage to begin. I have two Purdey barrels in my workshop and two William Powells The Purdey guns have just been done by someone with hot salts and are already showing signs of weeping white crystals. the Powell barrels were done some time ago both are rusting badly down the side of the ribs pitting the metal pretty much the same will be happening under the ribs, I often get fairly new guns made in Spain and Italy that have been finished in salts and the ribs have popped, a fair few Perazzi guns too. I was always taught never to use hot salts on barrels, that is just my view I am certainly not telling anyone what to do. I think it is a cost thing hot salts is cheap to do, rust blueing not so cheap but rust blueing done properly looks better and is much harder wearing.

Paul,
While I agree with pretty much 95% of your insightful post (nice to see you posting again btw!), don�t you think with all the fairly modern guns out there sporting hot blacked barrels (I�m talking probably in upwards of a million, ie. Citori, SKB�s, Beretta, Rizzini, Zoli, Ruger, Remington, Winchester, Chapuis, Verney-C, etc) that there would be more incidents that just a few popped here and there or reports of catastrophic rusting of all these millions of sets of barrels out there that have been hot blacked?
I think manufacturers pretty much have it down to a science. Don�t you? Terrible looking hot blue jobs are caused by all sorts of different factors...the reasons are myriad! Bad salts. Cheap salts. Poor prep. Too high of a temp. Too low of a temp. Metal composition. Hobbyist.
There�s been test done that show how durable hot blacking is compared to other finishes like rust black and nitre. One local rifle maker took coupons of the same steel barrel and finished them in all sorts of finishes...rust, hot, nitre, hi tech coatings, etc. and then tumbled them in media. The hot black came out on top...so that�s what goes on his very expensive custom rifles.

I don�t know what the manufacturers method is for neutralizing the salts after the bath to prevent further rusting/oxidation from occurring, but whatever they�re doing must work somewhat well or all of us who own a fairly modern gun would be handling a rusty pipe with no ribs.

The Purdey and Powell barrels you mention...that is damn near criminal. My goodness, what a disaster.

`Hi, I get your points too, I guess I only get to see the ones that have gone wrong, I would love to go visit all these makers and see how they all go about it. A modern version of an Angiers book would be interesting but not sure they would contribute. Not so sure about salts black being tougher than a rust black but I guess it depends on the formula and process used with rust blacking, I have some that come in that are tough to prep others you can wipe off with your hands, it is a very interesting subject. I haven't posted for ages as we are moving into gunmaking now with a great name so there has been lots going on here behind the scenes and not enough hours in the day. I hope your well.

I bought a 20 ga Sterlingworth from a guy that said he got it from the daughter of a man that died many years ago. It was stored in the basement muzzle down in a soft gun case that had disintegrated. He told me the stock was cracked the gun didn't work and had some external pitting at the muzzle. I'm getting a pretty bleak picture of the gun but when he showed it to me it didn't look all that bad. I fixed the stock and strip cleaned it. Turns out the original owner had the gun reblued. The gunsmith that did it hot blued the entire gun and left all the parts in it when he did it. The frame now has a purple color to it. That was the reason the gun would not work. He did not go crazy with the buffing wheel either as every thing is sharp. I was concerned about the hot blue on the barrels but this blue job was done about 40 years ago and the barrels look very good to me. I thought when I started to shoot it that the ribs might come loose but after owning it for 10 years and putting a couple thousands of rounds thru it I think it is pretty sound and am not worried about it at this point. I guess it all depends on a number of different factors.

I have had two doubles, an L.C. Smith Ideal grade and a Lefever F grade that had been hot blued long before I acquired them. My experience is the same as tanky had with his 20 ga. Sterlingworth. The ribs remained tight and solid. The solder joints never showed any sign of deterioration.

In spite of that, I would never recommend hot bluing a soft soldered vintage double. We know for certain that hot bluing salts are corrosive to tin/lead solder. We also know that many doubles have imperfect rib solder joints that can allow these salts to become trapped in the void between the barrels, and the salts willl eat away at the solder and the barrels.

But solder is not porous. In fact, it is a very good sealer, and that is why it has been used for decades to perfectly seal plumbing joints which continuously hold liquid under pressure. So if a corrosive agent such as bluing salts is completely rinsed away and neutralized, any potential damage is stopped then and there. On the other hand, if any bluing salts at all is trapped between the ribs, or in a small void in the solder joints, it will slowly attack and destroy the joint.

Think about this... there are a lot of old shotguns that have sections of rib pop loose. The vast majority have never came within a mile of a hot blue tank. The joints fail because of physical damage, or more likely, because they were poorly soldered in the first place. The greatest cause of solder joint failure is contamination and poor preparation and cleaning of the joint surfaces. Other factors are use of the wrong flux, or not using the correct alloy of solder.

I had a DH Parker that was hot blued. I used the old 10 bore to hunt ducks for about 5 years without any problems and then put the old girl in a gun rack. After another 10 years I noted several loose spots. Wheni sold it you could have removed the ribs with a mild tug. bill

Good points, Keith. This is getting interestinger and interestinger.

Maybe that "walking dead man" can be pardoned, under the right circumstances?

SRH

Another major culprit to think about is the type of cheap flux that was used in the joining of barrels of mass produced guns. Acid flux was commonly used and most of the damage is done out of sight...between the barrels. The damage it causes allows joints to become compromised and over time...eventually fail.

This is likely to cause some argument and is not a recommendation, it is an observation instead. I often mention my old friend Walter Grass, in his business, he built drillings and doubles, mostly O/U doubles. The barrels were soldered together by a local "rohermacher", and I never met or talked to him. Before rust bluing the barrels, however, Walter had to do the final cleaning of solder from the joints. It is very difficult to see solder residue on polished steel barrels. Walter used hot salt bluing to be sure the residue was gone. Of course, I asked him about this, since it went against everything I had learned. He held to two very important rules. First, this was only used on new barrel bundles, that had never been blued before. The second rule was the time the barrels were in the bath. He insisted that the barrels not stay in the bath one second longer than 14 minutes. The salt bath was also useful to remove solder residue from bolt guns, where sight bases or clawmount bases had been soldered. In these cases the two rules didn't apply because the solder joints were the full width of the bases. He believed mechanically removing the residue with chisels, scrapers, or abrasives stood a good chance of undercutting the thin joint at double gun ribs. This undercutting also can cause the rib to "pop". It has been my observation that when a rib does "pop", it is caused by rust on one side of the joint, and solder is left on the other side i.e. the solder was not eaten away. Walter told me that in the very old days, the entire barrels were tinned to prevent rust under the ribs. This didn't carry through due to the work required to clean it up before bluing. As to the wear of rust bluing compared to salt bluing, in my opinion rust bluing is better. The solution is called the "biter" because it bites the metal. The resulting "rust" leaves microscopic pits. The metal inside the pits is also turned black in the boiling. To wear the color away, the metal has to be worn away past the bottom of the pits. This is my opinion and it won't upset me if someone has a different opinion.
Mike