doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Chemical reaction from guncase

Several folks in our group got into a general discussion about what case component could cause a chemical reaction to the action surface on coin finished doubles. We have (2) identical guns and cases - both actions turned black and required a professional to refinish. Note: the bluing or wood was not affected with either gun.

These (2) high grade doubles were stored in European low cost plastic trunk style cases lined with felt. The guns were stored for approximately two months with the lids of the cases open. I know that we have several chemists in our readership. What is the most logical cause of the chemical reaction - the case plastic, the felt lining, or the glue that was used to secure the felt to the plastic case. I've never heard of this type of problem before.

George, I am not certain what caused this problem, but offer a thought or two. If the case were made of vinyl material, it could be the degradation of the material causing it. Think of the coating of your windshield from the gases from the vinyl dashboard.
It could also be formaldehyde gas from the adhesive in the case.
Best,
John

Coin finish offers very little protection from oxidation or other chemical reactions. In a lot of cases coin fin is nothing more than matte surfacing on the carbon steel base metal. Perazzi offered it in the past on some of their competition guns but when I enquired about it at my latest order I was told it was discontinued due to same. I doubt you'll get a definitive answer here on the culprit.... plastic degradation, VOC's from solvents, etc. unless you can positively identify the exact plastic in the case, chemical composition of the felt and adhesive, etc.

I would first have to know exactly what "coin" finish is? I know it looks like polished steel but is it a coating, like silver perhaps? As you can see I know O about the subject, but if it were silver (tarnish) it could explain everything. Just a thought-someone enlighten me. --- John Can.

What guns were they George ?

John C is on the right track IMO. Steel that was polished would not turn black. Black is the color of silver oxidation. I would venture a guess that the guns were true silver plated thru the silver nitrate solution process. So, I think we're looking for an outgassing of something that would cause silver to oxidate inordinately fast.

George,

I'm thinking it's the guns themselves plus plain old air, not the cases. What was the make of gun?

That the cases were left open is telling. If it was the felt or felt glue, then I'd think the side of the gun touching the case would be affected much more than the side of the gun exposed to open air.

I can't think of anything that would outgas as an acid. Organics (solvents) outgas. Formaldehyde isn't going to be acidic and it's a common glue residue.

If the plastic case was PVC I truly doubt that it could degrade sufficiently to release HCl gas, which PVC will do when burned.

Two months could be enough time for unprotected silver to tarnish in South Carolina. I would think silver plated guns are rather rare though.

The original poster still hasn't answered on the gun makes. Are we dealing with modern or vintage pieces? If modern, why would a mfr. silver plate a gun receiver when there are much better looking, more durable, and cheaper finishes that look like coin? If the guns are more of a vintage type, the so-called coin finish is usually just matte polished steel. In that case the steel may have some alloying metals that make it less resistant to oxidation. For example the Chromox alloy used by A H Fox. In either case, modern or vintage, I think the resident alchemists here should forget about the black tarnishing common to silverware. I really doubt the receivers on many high grade doubles were silver plated. What are the odds of finding two with the same problem at the same time? Polished steel will definitely turn black - that's the bluing process - although it usually involves boiling & high heat to convert the ferrous oxide into ferric. I suspect another reaction is at play here but without knowing the type of plastic, felt, oil or rust preventative compound used beforehand, etc. we're all going to be shooting in the dark.

Don't leave ceratin slip-on pads on for long (even leather ones) or you will not like what you see when you take them off later!

I had trouble with the nitride finish on my K-80 discoloring and a friend used a Birchwood Casey lead remover cloth to clean it. It was fast, easy and the results were SUPER!!! Just use it like a silver polishing cloth and lightly oil the reciever when you finish.
bill

If it is silver? and I suspect it is, it may not be so much plated, as a silver "wash" similiar to what is done in gold to the inner works of some doubles - very thin would be a kind description. If one has natural gas for home use, heating etc. it won't take long to oxidize silver to "black" for some reason probably the inherint moisture. I don't have a Merck Index to find what all turns silver black, could be a lot of chemicals. Jag, I would be reluctant to leave on any type of slip-on due to the chemical retained by leather-isn't lye? (caustic soda) used in tanning leather and caustic residue could easily be present add a little moisture and bingo ruined finish. As far as rubber goes it breaks down with time and the resultant "brew" might be a good finish remover. --- John Can.

John,
The silver nitrate solution process is a form of electroless plating. Agreed, it is super thin. Over the years, mfrs like Browning/Miroku, Win/Kodensha, and others have tweaked the methods and alloys. I recall one Citori of silver nitrate finish that was clearcoated from the factory, but soon wore off in the usual places from carry. The silver finish turned a gray/black in the area of wear until it too wore thru to the steel. I had a 101 Pigeon with the same silver nitrate finish and similar things occurred.

For a silvery finish that "Won't" wear off --- try Metalife. It is a chromium stainless finish. The best wearing, non staining finish I have ever seen --- used it for years on some client guns. Ken

I'm attempting to reach the owner of the two guns. Another friend just corrected me about the case material - these two cases are oak and leather and not plastic cases as I had previously reported. The (2) guns are high end Perazzi's and the owner lives in Virginia not SC. I'll attempt to get additional details concerning the year that the guns were manufactured, the model plus any additional info he can add. I'm also curious to learn if only a portion of the action in contact with the case turned black or if it was the complete action.

Perhaps a bit OT, but I learned from experience not to wipe my Merkel silver nitride with a silicone impregnated cloth, as it turns the silver nitride to an ishy rusty brown that is difficult to remove.

John

Could be the very air as noted depending on the "silver" coating.

More likely to be glue or process used on the leather. Ask anyone carrying a silver item in a Coach purse...

A clue is usually that the problem generally occurs more on the side away from that resting on a surface.

IN GENERAL, a light oiling should help prevent this.

One test might be to take the gun out and replace it with a piece of silverware for a week or so.

Might also suggest wrapping the guns in sleeves made of Pacific cloth which many of us do for transport in leg o'mutton cases.

Mystery solved (maybe). Cases are OAK and leather. Leather is hygroscopic, and oak has tannins that will turn ferrous metals black. That's why you seldom see steel or iron hardware on vintage oak furniture. The usual brass hardware was not just for looks, it was to keep the tannins from attacking steel hardware. Topic is covered extensively in vintage cabinetry and contemporary refinishing books. The moisture attracted by the leather in a relatively humid climate combines with the tannins and creates the black color on the guns.

Where are the chemists?

Posted on 10/7 in the morning:

"I think the resident alchemists here should forget about the black tarnishing common to silverware........ I suspect another reaction is at play......"

Hmmm, I don't have this problem in any of my oak and leather cases. Just saying.

I just talked to the Virginia owner of the guns - it's getting more interesting. The (2) guns previously mentioned are Perazzi SCO Models. The pair of Perazzi's, I now learned, were in a single double oak and leather case. A third gun was also involved (new info) which was stored in the second oak and leather case made by the same case manufacturer. This third gun is a Piotti Monaco No.3. also coin finished. The owner did not know the specifics of the finishes applied to the actions other than they all had a coin type finish.

He commented that the blackening happened over a one week period and covered all sides of the coin finished actions (3 guns) plus also had red rusting on other exposed steel surfaces. The guns, over this one week period, were stored in the (2)cases with the case lids open sitting on a pool table top in circulating room air.

The (2) cases were sent back to the maker and new case linings were installed - he believes ultrasuede. The owner has not used the cases since other than to put some chemically cleaned nails and steel wool in the cases to look for any potential rusting problems - so far, so good. He thinks that the problems may origionally be related to either the lining or glue used. The
case manufacturer has not offered any explainations.

That is what those fancy gun safes with glass fronts are for. These are very expensive but look like fine piece of furniture. They will look great in library room of your colonial villa.
Cheap cases are just for transporting those guns to be sold. They can keep that pos and everybody is happy a "win, win" situation if you will.