"Plum" bluing

[silicosys4]

Hello,
I have a question that hopefully someone can answer.
Why does the bluing on some older guns turn a "plum" color over time?
Ruger is particularly notorious for their bluing going "plum", I have a 3 screw single six flat top from the mid 60's that is VERY plum, I mean a wine colored burgundy.
From what I have seen, its not just a formula used for a short time, It seems to be a consistent 25 year long problem with the consistency or formula of their tanks...I have seen Rugers from the 60's all the way through the 80's with plum bluing, both their pistol frames and rifle receivers. Of interest to me is that ONLY the frames and certain parts of the guns plum up. I have never seen a plum revolver cylinder or barrel with bluing going plum, so that leads me to believe either there is a different bluing process or formula used on those parts, or the characteristics of the metal is different and doesn't cause plumming, or both. I have seen a Ruger P89 slide that was a beautiful plum color though, so it happened on more modern guns too.
I have seen other guns from the 60's and 70's with plum bluing, but Rugers are the most common.

I personally like the effect even though I realize it is unintentional and undesirable from a manufacturers viewpoint, and have purchased guns specifically because I liked how they looked with a flawless plum finish. Is this "plum" coloration specific to bluing processes that are no longer in use, or unavailable because of EPA changes? If I want to restore a plumming finish is there any way to get the same effect with a refinish?

Thanks for everyones answers

 

[silicosys4]

Plum Ruger

Here is a picture of what I am talking about
My single six is about this hue, maybe a little more burgundy.

 

[steveno]

I read somewhere that one of the causes was the steel content and alloys used with investment castings. I have a 41 Blackhawk that shows some of the plum color but I long since stopped worrying about it

 

[1KPerDay]

Dunno... but my AC41 P.38 is a nice plum color.

 

[JellyJar]

I think that...Ummm Plum!

(Homer Simpson)

 

[ford8nr]

I think it had to do with the time. I have an old Win 52 and Win M12 that are plum blue.

 

[Larry Ashcraft]

I think it's the metal content. If you re-blue a nickel steel 1903 Springfield, the action will turn plum.

 

[Jim Watson]

Brownells says it is sometimes the alloy, some times the temperature.
I had a Caspian based gun that was apparently run too hot and it came out plum red. As it aged it turned a rather handsome golden bronze color. I should have left it that way, but I had him do it over in ordinary blue.

 

[Tommygunn]

I don't know about it being unintentional....
I have a Uberti repro of the Winchester 1873 which has a plum-blue receiver. The sideplates and other metal are normal black-blued and the overall effect is very attractive -- IMHO.

 

[oneounceload]

There are also some HK P7s that have the "plum" slide - it isn't a defect as far as strength

 

[Blackhawk30]

Its still going on.I have a pair of Ruger LCPs that have plum mag buttons.I've heard its caused by alloy composition and heat of the metal being blued.

 

[il_10]

Arsenal refinished soviet SVT-40's had a plum blue bolt carrier; I've seen it in a few other places as well. I've always heard it has to do with the composition of the alloy, and I've never heard of it as having to do with time. Are you confident that your plum-looking blued guns didn't start out that way, but rather were originally a dark blue and sort of faded into the plum blue?
In that case it could have something to do with the way they were stored. For example, a WWII era SVT-40 would have been stored in cosmoline for a long period of time. Perhaps the petrolium had something to do with the discoloration of the bluing when combined with the particular alloy of the bolt carrier?

Also, in that particular rifle, the plum color is only manifest in the bolt carrier, not the rest of the firearm. I don't know what that means, but I think it's a pertinent observation. Also, in a ~1950's Colt Detective Special I personally reblued using the drain-out home-brew method, the barrel and cylinder have taken a more plum looking color than the frame, though everything was prepped the same way. Again, I don't know what this means, I'm just providing more data. Though it might suggest something to do with the heat-treat or temper assuming the entire firearm was made from the same type of steel, which is uncertain as well. In the case of the colt, perhaps someone like Old Fuff could chime in with more pertinent insight?

 

[Dr.Rob]

I have a Colt Commander from the 50's with an Aluminum frame that is turning a plum color.

I have a Czech Mauser that the extractor claw is purple--every Dan Wesson I have ever seen the frame goes that dark plum. never the barrel or the cylinder, just the frame.

 

[TennJed]

the safety and extractor on my Makarov is plum

 

[Dr.Rob]

I think the East German ones the plum parts were that way from the start.

 

[Sergei Mosin]

See http://rugerforum.net/ruger-single-action/82713-plum-colored-bluing.html for an explanation from a gunsmith.

 

[aarondhgraham]

My 1892 Lebel is turning plum as well,,,

My 1892 (made in 1903) Lebel is turning plum as well,,,
In actuality though, I kind of like the color.

When it's freshly cleaned and oiled,,,
It looks very nice with that tint.

Aarond

.

 

[hardluk1]

I have a large frame DW revolver that has a plum colored frame but blue on other parts that of a different steel alloy. Don't mind it but wish it was that color all over.

 

[303tom]

I am not going to tell you why some firearms turn a reddish plum color, I am going to ask you a few questions & maybe you all will figure it out on your own. Some of the older firearms were Browned, which is a controlled rusting. Now what color is rust ? Now if you mix the color of rust & blue together what color do you get ?...............

 

[BADUNAME30]

Because the metal has a higher nickel content.
Like the older Winchester '94's. Actualy, a lot of older Winchesters were high in nickel.

 

[Fleetman]

Guns & Ammo ran an article a while back written by, I believe, Garry James, and he said earlier plum-colored Rugers are sought after by collectors. Search and you might find you have somewhat of a prize.

 

[Deltaboy1984]

They are cute and it doesn't how they shoot.

 

[Dnaltrop]

my '87 Blackhawk has a nice dark plum on the loading gate and hints here and there on the sides of the frame.

I'd love to find one in a completely dark purple, whilst having the money to buy it.

 

[HOME DEPOT GEORGE]

Here's my Supermag with a nice plum color. It's somewhat common on the old Dan Wesson revolvers

 

[silicosys4]

I have a Colt Commander from the 50's with an Aluminum frame that is turning a plum color.

I have a Czech Mauser that the extractor claw is purple--every Dan Wesson I have ever seen the frame goes that dark plum. never the barrel or the cylinder, just the frame.

Can we get a picture of that Commander? That sounds neat! I didn't know aluminum anodizing could do that...or is it a different finish than anodizing?