What causes bluing to turn " Plum "??

HKP7 slides have a tendency to be plum, some more than others. This is one of mine, one of the B grade's I purchased. The P7 forum had lots of technical discussions on the "plum" as well. Seems like there's two schools of thought one saying it's the type of steel, the other saying it's in the bluing process.

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My Model 10 has a plum barrel, sometimes noticeable, sometimes not depending on the light. Looks just like the one pictured earlier in the thread.
 
Having been in the refinishing business for many years as well as doing work for some of the gun companies through our shops, all of the points ,views above ( except for the WD-40 comments) can and will be 'true" ,,,,this happens at times for ALL of the companies, and usually MORE of an issue with the Rugers, as they are "cast" 4140 chrome-moly and the batches made for these castings,MUST be "perfect" or the parts will 'plum' or 'streak as noted above.....nature of the beast...yes, for the MOST part,one must carfeully look at the gun,or the parts as this is a "fault" found all too often in aftermarket ,rebluing by many shops...have to look carefully (inspect) that the gun was NOT "improperly reblued"....
yes, the terminology of the wording for "sand" are all to often twisted, but for the most part,mean the same thing...its their application that changes for the process of the steel making itself, or the casting.......
 
kenpofan said:
Per my learned collegue (johnlevick ) the cause is properly attributed to silica in the steel..


"that plum coloration is a result of a slight excess of silica in the steel,and not WD40. "

The Internet has also spawned the WD-40 caused it..

I share John's skepticisim about that particular cause..

I've used it extensively as a wipe down agent without a problem.
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Huh. I get quoted in the first reply, and this is the first time I've looked at this thread! Looks like most of the queries have been answered. I'd just add that while I'm not a metallurgist, the effect of silicon causing the "plum" color was originally explained to me by an old gunsmith who does some of the most beautiful hot bluing I've ever seen, and was confirmed by folks at Essex Arms and Caspian, both of whom manufacture cast 1911 frames. I originally asked the question after my old gunsmith friend blued an Essex frame for me, and it came out of the tank plum colored. Other parts of other guns, including the forged slide I'd fit to the Essex frame, coming out of the same tank at the same time, came out a beautiful, deep blue. Obviously, it's not the bluing salts. It had no WD-40 applied, so it's obviously not that either. And no, WD-40 has no silicone in it, nor silicon, for that matter.
 
When some one figures it out , please post it I might want to turn some of mine purple .
 
WD-40 on Guns

I have been using WD-40 on my guns since about 1970 exclusively. I use it for cleaning and lubricating, and I clean my guns after every range session. Guns I have had since that time still show the the original blueing without fading or discoleration.
One must take care to reduce or eliminate the WD-40 inside carry guns as it can penetrate the primers. I have a small air compressor to blow unwanted WD-40 off and from the inside of the firearm. I also use WD-40 for long term storage and have never had any problem with rusting on any gun.
For lubrication of the slides on my semi automatics and on the inside of my revolvers I use Break Free CLP.
Just thought you would like to know.
 
Bluetec-320 said:
I have been using WD-40 on my guns since about 1970 exclusively. I use it for cleaning and lubricating, and I clean my guns after every range session. Guns I have had since that time still show the the original blueing without fading or discoleration.
One must take care to reduce or eliminate the WD-40 inside carry guns as it can penetrate the primers. I have a small air compressor to blow unwanted WD-40 off and from the inside of the firearm. I also use WD-40 for long term storage and have never had any problem with rusting on any gun.
For lubrication of the slides on my semi automatics and on the inside of my revolvers I use Break Free CLP.
Just thought you would like to know.
Click to expand...




Hello
I was told at Lowes Department store by the Lock Smith, to never use W-D 40 On a Key Lock. He shared with me that W-D 40 has a certain amount of Water in it's Chemical make up. I don't know if this is true, :confused: but I started using "Corrosion-X" What I use on all My revolver's and never had a problem after that... Corrosion-X also straightened out my Grandfather Clock that quit chiming and it has run flawless ever since. My vote goes to Corrosion-X Products..;)Hammerdown
 
My newly acquired K frame 3 inch model 13-3 has a plum barrel. I didn't even notice it in the shop. I observed it last night with a flashlight while he was having his bath.

It's ok...I still love him regardless of his little purple snout.
hug3.gif
 
None of my smiths show a plum color, yet. However, I had a GI M1 carbine Blued (I know, they're supposed to be parkerized...mea culpa) and the lower receiver came out bright....plum. Saw another sinner with a GI UPM M1 Carbine that had also been reblued and surprise, surprise, it, too had a plum colored lower receiver! As far as we know, we have different smiths and we both asked why the plum color. Common answer: the lower receiver (trigger guard to mag well) are made of harder steel.
 
plum color

Just my two cents worth. At one time I had a model 94 that had been reblued and was the plum color you spoke of. My gunsmith, P.O. Ackley, a noted barrel maker and author on "Guns&Ammo, said the plum color was due to taking the part out of the bluing tank too soon. He reblued it again, and the '94 came out a beautiful dark blue/black. I guess there are more than one answer to this condition.
 
I think that all of the answers point to one common problem but not WD 40. Bluing of steel is a difficult process. The bluing salts get weaker with age, the temperature of the steel has to be correct and the grade of the steel varies from gun to gun or part to part. If any of these factors enters into the process, the bluing is affected and the result is eventually a plum looking color.

Actually, bluing is an incorrect term. The process was originally referred to as browning. Basically it is a controlled rusting process that was applied to firearms going back to the 16 or 1700's. The purpose was to remove the shine of the steel on hunting guns and to retard the normal rusting process. It is the combination of chemicals or salts used that causes the gun color to go from a brown to a dark black. Smith and Wesson changed their "bluing" process and this is why the older guns have that deep dark black blue finish that is not seen in the modern guns.

The plum barrel and cylinder condition is a result of an error in one of the process steps. The steel takes on more of the brown color which makes the blue look plum.
 
I have assisted my gunsmith with the bluing of many guns over the years. Occasionally a part comes out of the tanks purple. As we do the bluing in batches, I cannot attribute the color to anything other than the formulation of the steel. We may do multiple 1911 frames, and once in a while one comes out purple. The parts that can usually be counted on to turn are Essex frames and O3A3 receivers. My first Bullseye pistol that he built for me had a deep blue Remington slide and a purple Essex frame. They were both prepped and blued in the same batch. By the way, after the parts come out of the final fresh water rinse, we immediately hose 'em down with WD40. I have rifles we blued 25+ years ago that are the deep rich blue today that they were when they came out of the tanks.
 
I think the 'plum' color just indicates that it is ripe, just like the fruit, and ready to be gathered in for the winter.
 
Alloy differences and heat treat is what I understand. The first Wby Mk V I had was straight from Roy Weatherby himself in the 50's. I had it barreled to a 270 Win. (yes it was a standard bolt face) After bluing the receiver was a real pretty plum. If I remember someone there said the nickel content did it.

Also there is a plum spot on my Anschutz 1413 at the harder lug lock area.
 
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I've got a pre-model 15 Combat Masterpiece (1954 manufacture) that has a plum cylinder. Definetely different.
 
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