What causes bluing to turn " Plum "??

[nachogrande]

YOU CAN'T HANDLE THE TRUTH.

IF a complete/scientific explanation, on the molecular level is given , you may be asleep by the 3rd sentence. The readers digest answer IN LAYMENS/SIMPLETONS terms PLEASE.

 

[steelslaver]

A lot of things can cause it.
I can attst to heat treatment changing how steel blues. If I do a blade in such a way that I only harden the edge by using a controlled depth quench, the hardened edge will blue much darker than the spine area, if I blue it. If I harden the whole blade then draw back the spine of the blade to a softer temper that blade will color differently than the edge quenched one. If I use 1095 high carbon and 15N20 (3%+ nickel) to make damascus the high carbon will blue deep and dark and it will hardly effect the high nickel content 15N20.

 

[stansdds]

And this thread died nearly 9 years ago. Just sayin'.

 

[JH1951]

The thread may be dead in the eyes of some, but it's quite like reopening a cold case homicide, the issue still has really not been put to bed.....
I will add that a plum color on a piece is not necessarily an indication of a reblue, but for me, it is a red flag that goes up and I must look much closer to see if there are any other signs of a refinish. I have seen many refinished pieces show plum - I have owned several that were that way out of the factory door.

 

[mike from st pete]

My recently purchased 10-5 snub has a bit of plum showing on the cylinder and barrel. Only shows in strong outdoor sun light.

 

[4011]

Many years ago I had a neighbor who Blue guns once a year. He took an Iver Johnson 410 that I had for my son. It was old then. After trying three times to get the receiver to go black he gave up. He was so sorry it didn't work out. Well the bbl. and the hammer an trigger were beautiful black. The receiver was very plum. Very pretty gun !!!!!!!

 

[Gunhacker]

Well... I had several of my N-frames from the late 70's and early 80's where the barrels went plum on me after I put them in silicone impregnated bore stores for storage in my gun safe. And on portions of the frames, a milky looking haze developed that will not come off with any conventional gun cleaner I've tried.

The guns were continuously in the bores stores for about 6-8 months until I went though everything in my safe to do my usual pre-winter inspection and "winterizing" regimen.

Needless to say, I've long since discontinued using the bores stores.

 

[cmansguns]

You guys have already answered the long standing question and the "plum" color comes from you shooting the wrong variety of PLUM, or being too close, so back off to 25 yards.

There are 3 types of Plums, American (Blackamber), European (Seneca), Japanese (Satsuma). ALL are grown throughout the USA. Quit shootin at the Jap and Euro on the trees, and either pop for some regular targets, or switch the Blackamber American and that "oversplatter" won't cause you "no mo plum parts".

Tongue in cheek of course, but if the original manufacturer and designer of the actual plum fruit tree could not figure out what caused different color variations.....how is this Forum going to answer it for metal?

 

[MG&L]

Hmmm...

I have been smithing for some time, and I have experienced some contradictions to the comments in this thread about plum coloration. Just yesterday, my wife and I blued a batch of rifle parts. This morning when I wiped them down, I saw what I have seen before randomly over the years. The bluing on the vast majority of parts/barrels/actions/bolts, etc., turned out quite nice...deep dark black. However, three parts plummed.
- All parts were in the same bluing process (in the tank at the same time for the same length of time).
- Temp and salt mix was consistent throughout.
- I do not use WD-40.
I will not claim to know the answer to the plum dilemma, otherwise I would have taken action to remedy it if possible. BUT, I will say that I have witnessed particular parts on particular firearms plum more than others. For example, Mauser extractors, front sight ramps on many older (military and civilian) rifles, H&R Topper receivers to name a few. While I understand if the bluing recipe is skewed or temp is off, the desired effect will likely not happen, but my experience has shown that consistency in bluing also produces the undesired plum effect. I put little solidarity in the WD-40 theory (if you believe it may have some effect, it certainly is not the only culprit). My belief now, as it has been, is a difference in the steel. Parts to a single gun do not come from a single piece of steel. Is Silica the culprit....is Nickel....is it something else? Smarter folks will be able to determine that. My degree is not in metallurgy, my intelligence in that subject is decent, but not exceptional. A second rebluing has, on occasion, has provided slightly better results with an adjustment to temp, but not always.
Cheers & Happy New Year!

 

[PALADIN85020]

Older Ruger revolvers, such as this "flat top" .44 mag Blackhawk from 1957, were rife with plum parts. Check the loading gate on this example. I've been told that the plum color had something to do with the composition of the steel rather than the bluing process. At any rate, the plum colored parts are indeed desirable on these guns as proof of era authenticity if nothing else.

By the way, the Sambar stag grips shown are are original. Both stag and ivory were extra-cost options at that time.

John

 

[Drm50]

I have a custom rifle on a 98 Mauser. The barrel Douglas and was their latest new steel in the day, middle 60s. The gunsmith who made it up was known for his bluing. When he blued this rifle the action was perfect and still is. The barrel came out pleasingly PLUM. He wanted to reblue but we just left it that way, it has character.
I have old Ruger Single-6 that has a wisp or two of purple on the frame. I have never herd WD causes purple. I think whoever started that one is full of brown.

 

[rkittine]

I have some HAM Radio amplifiers where the Heat Sinks are Blued and have had the same thing happen. When checking with the manufacturer, they said it was not an uncommon occurrence. They told me that it was due to impurities in the steel. Of course for this application I don't case, though it would upset me if it happened to any of my Blued Smith firearms.

Bob

 

[THE PILGRIM]

Had an early flattop Ruger 357 with the bright Purple Blue Loading Gate.
MMC Rear Sight.
On my list of what was I thinking?

 

[2152hq]

The NIB M57 I bought '67 ('S' prefix) had it's cylinder turn plum.
Rugers are noted for the color.
Rebluing those older cast steel framed SxS and single shot break open guns will often leave the frame purple.
Lots of Mausers, Springfields and Lee Enfields reblue OK but then can sometimes change over to plum with some time.
There's a mix of case hardened recv's there .
I did a restoration on a Ross 1910 Sporter that had been 'refinished'.
The receiver was a deep plum color from the hot salt reblue. The bbl was a deep blue color when I recv'd it.
Both had been heavily buffed and the bbl had not been taken off of the recv'r for the bluing process. So both parts recv'd the same polishing compound, prep, oil, cleaner, and tank bluing time.

No strict rules,,no simple answer it seems.
Some blame the investment casting process, but forged and machined parts seem to be effected as well.
Poor bluing salts, temp, time in tank, etc.

There are probably thousands of different steel types then add the different heat treatments they can be given.
It's a wonder anything matches coming out of the hot salt blue tank.

Winchester always had a problem matching color when using the Carbona Blue process as well.(Discontinued use in '38/'39 and switched over to DuLite hot salt bluing)
Especially on the Mod42 where the side plate was soft and the frame HT'd... and on the Mod21 where the frame is Ht'd very tough but the trigger plate which was made of the same alloy recv'd no HT'mt at all.

FWIW,,most parts that refuse to blue w/hot salt blue or turn unacceptable colors like this will generally blue just fine if done by Rust Bluing.
Slow Rust works the best on parts that give problems.

Thanks for giving the old thread new life!

 

[marct375]

At some points in time S&W revolver parts were blued separately in batches. Depending on the materials/ prep etc. variations such as "Plum blueing" were the result.

 

[PeteC]

At some points in time S&W revolver parts were blued separately in batches. Depending on the materials/ prep etc. variations such as "Plum blueing" were the result.

Not just S&W. There are Beretta semiautos that never left Europe (and never saw WD-40), with plum color slide stops and other small parts... Physics in Every Day Life... or Chemistry!

 

[sheepdawg]

How about a 40 year old Leupold Vari X II in plum.

 

[diyj98]

I have just accquired a 28-2 that the barrel has turned "Plum", just the barrel not the rest of the gun.. looks perfect.. but plum??
Can anyone tell me why? this happens.. I have seen it once or twice on other Smiths..
THX
Sal

I can't tell you why, but I also have a 28-2 with a plum barrel. I've listened to a local S&W "expert" tell me several times that my barrel has been reblued while rolling his eyes, but I just continue to ignore him.

 

[PeteC]

I can't tell you why, but I also have a 28-2 with a plum barrel. I've listened to a local S&W "expert" tell me several times that my barrel has been reblued while rolling his eyes, but I just continue to ignore him.

It seems to occur more often when some parts are heat-treated or processed differently than others, but I do not know enough about S&W to say this is the case here. The explanation of different parts being blued in batches seems just as valid.

 

[steelslaver]

Here is something else to add to the mix. Some cylinders are harder than others. I have made about 8 22 cylinders into 32 cylinders. I have ran into 3 that were considerably harder than the rest. The one in my shop right now if the hardest of the lot.

The heat treatment a steel has gone through will effect how it blues and retains its color. I have put parts in the same tank at the same time and they do not all respond the same, some take longer, some I actually take out and dip in water to cool off, then wipe with fine steel wool and put them back in solution trying get them to match.