Guide to Re-Strawing your parts?
 

I have searched the forums using every key word I could think of, and found lots of references to it, but can't seem to find an exact procedure on how to straw blue parts.
I found two promises from John a year ago to make this a sticky, but that doesn't seem to have ever happened.
I wonder if there was a decision made NOT to post it...
Does anyone have a link to this procedure, or have a copy of the Instructions that one of the members was circulating a year or so ago?
I have jumped whole-heartedly into re-doing my shooter, and need information on this process.
Thanks in advance!!!
Zamo

Zamo,

Here's a reprint of an article that was posted by John Sabato on 10/5/2006. I'm sorry I didn't give him due credit when I re-posted it here.

Good Luck Zamo! Post some pictures of your results.

Dave in TN.

A process for creating straw� color finish on steel gun parts

Strawing� or coloring small steel gun parts with heat is a fast and simple process. Do not try to make it complicated. If the process does not go smoothly just stop, and take a break, and then start over again. You can not mess up the outcome, but you may have to start over, especially if you have achieved a color darker than you wish. You will just have to re-polish and then re-heat treat the parts again until you get the color you are trying to achieve.

Buffing can take a toll on proof marks and serial numbers so you want to be cautious. I learned this process. This process originated from Harry Jones, author of the book Luger Variations,�as used by him in his California shop some 35 years ago. This process has been used successfully to straw color the small parts on at least 400 plus Luger pistols all over the world since then.

On the checkered areas, such as the magazine release and take down lever, it may be sufficient to properly prepare these surfaces by just using a heavy wire brush. A fine wire wheel on a buffing machine is a good method to do this. Another method would be to use a small wire wheel on a Dremel tool to achieve the same degree of cleaning. The small parts should then be polished with 240 grit polish on a buffing wheel. You do not want to bring the surface to a bright mirror finish, as that would exceed the finish applied by factory work, and you should try to come close too what was done at the time of original manufacture. Tight and hard to get into places can be polished with approx 360 grit sandpaper.

The surfaces that do not show when the gun is assembled do not need to be polished, even if the part is already blue or patina. It makes for a more professional job if you do, but in areas behind the trigger, this may prove tough to get to. Also, if your ejector is pitted, you should polish it on the area that shows when the gun is assembled. You can also polish the underside of the ejector, but if removing pits on the under side of the ejector is going to make it too thin, then stop polishing after outside surface is done. Un-seen and un-polished parts will not affect the out come of the new straw finish on the polished areas.

Once polished, use something like gunscrubber to degrease the entire part! Also degrease the tools you are going too use for handling the parts during the strawing process. Heavy tweezers should be used to handle the parts once they are cleaned, and again as they come out of the oven. Degrease at least the part of the tool that will come into contact with the part. Even clean washed hands will leave some oils on the parts and this may cause the finish to be other than your objective so be careful. Oil of any type will mess up the finish during the strawing process.

Heat your oven to approx 450* (degrees Fahrenheit). The hotter the oven the darker the color result will be. But a hotter oven will also color faster, so watch carefully for the color you want and immediately remove the parts from the oven once you achieve that color.

Use 530* for a darker Krieghoff-type look. Use 510* for 1940-43 ejector temper blue. If you just stick with 450* you will very likely be fine.

Place parts in a small de-greased pie tin in the center of oven and stand back and watch the parts through the oven window. Right before your eyes the part or parts will start turning that magical straw color. Smaller thinner parts will color faster. Take the parts out of the oven individually once they achieve the color shade you want.

If the color is darker than you desired, you have waited too long so you have to cool the parts and re-polish. Then degrease and start over. Heavy thicker parts will take longer.

It is recommended that once you get the color you are looking for, immediately take the parts out of the oven and start cooling the parts with a light oil. 3-in-1 brand oil is recommended, but any sewing machine or light gun oil will work. Use several light drops, don't be cheap on the oil, but there is no need too have the part swimming in it. When the parts have cooled down to room temperature, wipe the excess oil with a soft cloth and install the parts. You will be very pleased with the results.

Strawing small parts is just that easy!

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Yes, the strawing does occur simply by means of the heat applied. It really is a controlled oxidation process. To say it occurs "simply" is perhaps an over simplification. A lot has to do with the preparation of the metal surface and the control of the temperature. As John's instructions indicate, thin portions of the metal tend to heat up faster than the thicker parts so the heating process needs to be applied uniformly, monitored carefully and the parts cooled/quenched relatively quickly when the correct color is attained.

An old trick is rather than place the parts on a pan and heat them up, fill the pan with clean (emphasis on clean) fine sand. When the sand has attained the approximate 450 degrees, push the part to be strawed into the sand (needle nose pliers or surgical hemostat are handy tools). The sand bath provides a uniform heating medium. Remove the part after a few seconds, check the color, and repeat as necessary to achieve the proper color. Quench immediately to stop the process. Like many things, color hardening is as much an art as a science.

Zamo,

Here's one more item you might need..... I found this in the Member Gallery #4. It was posted by someone whose initials are "Wm."

this is now stuck (a sticky means it stays at the top of the threads, so it can easily be found)

Look familiar......

So simple, yet so complicated, Thank You! Eric

My apologies to John Sabato and "Wm" for not giving them credit when I put up these posts on 12/12/2007.

Have a Merry Christmas and Happy New Year guys!

Dave in TN.:cheers:

Dave, I'd thank Policeluger, I am sure it is his information that John S posted for him...

After absorbing John's fine strawing instructions, I thought I'd follow them a couple days ago. I needed to heat, slightly reshape, and retemper a later 1937 S/42 ejector which I had finally identified as the cause of an occasional forward-pointing stove pipe jam; with another round already properly fed mostly into the chamber. The ejector was very slightly loose in its recess. It needs to be facing all the way inward, in the bottom of its seat, under slight tension. Most of the time it functioned, but not always.

With all other modern spring stock I have worked with, when heat treating, you stop with the color blue. I thought this time I would stop at straw, as I assumed the Germans were obviously using an alloy where this was the right color.

But remember, something changed in 1937; early parts were straw and later ones were all blue.

Well, I wanted to get this ejector just right, and if the process would work, I would bead blast and straw the trigger the side plate also, whether or not this is "correct" for my serial number; it looks nice.

Anyway, I uniformly heated to a red color, slightly re-shaped, quenched, and polished the outside surface of my ejector. I then set it on its side on a clean cookie tin in my electric oven, with front glass window and strong oven light. I guess my cat wondered why I was hunched on the floor on a step stool, staring into the oven. Humans are weird.

I planned to throw open the door the second the straw color appeared, showing that tempering heat was uniformly distributed through the ejector. I set the bang-bang thermostat for 450 F and waited. Coils glowed, the oven heated, and the polished surface stayed silvery, bright steel color. No straw color, or any other color.

Then at the exact moment the thermostat clicked off, the color of the whole polished surface changed to deep electric blue. This took under two seconds, and there were no intermediary colors.

I opened the door and cut the heat instantly, let the part air cool (NEVER put oil on such a spring immediately), and installed it. 200 rounds or so has showed the temper was correct; nothing broke or took a set.

My question to you advanced Luger experts is this. Do you suppose that sometime during 1937 the Germans changed their ejector specifications to an alloy which tempers to a blue color rather than passing through a straw color at around 450F? ...and that post 1937 ejectors cannot be "strawed"? Might this have been a part of the process in deciding that the "strawing" of the other parts was, and had been, a waste of time?

Or did I do something wrong? I make a lot of coil and flat springs from scratch, and temper them. I think I know the process. But....?

I went back and looked at my color charts, to see if I had made a mistake. Nope, straw and the other colors must come first, and I don't think I could have missed them, staring at this thing under bright light, while the cat gave me the fish eye.

Anybody else ever try to straw a post-'37 ejector?

And for those of you with strange infrequent ejection problems, check your ejector for a slightly loose fit in its seat. If you know how, this can be fixed without replacing it or breaking it by trying to bend it cold. Never do that with any spring.

Phil...

The strawing instructions are indeed Howard's (PL), but the reason they stopped strawing and started bluing in 1937 was not metalurgy but strictly to expedite manufacturing... all parts went to the same hot salt blue process because of the pressures of war time.

The hot dip blue was cheaper. The P08 was plagued by budget problems from day one, it was simply too expensive to make and all sort of cost cutting measures that could be used, while keeping to the military contracts, were taken. Even the military tried to force Mauser to change the use of steel types more than once. It's all about the money (and the illogical reasoning that exists within military acceptance committees).

Commercial Mauser's hot dip is very black and thick, including Interarms Parabellums.

How did they make the "layer" so thick?

John, Vlim, (and Howard), thanks.

I set out to get a different color, but the one I accidentally got is O.K. and pretty much correct...except that they blued theirs after tempering.

Maybe if I had a computer regulated heat treatment box, I could have nailed that strawing temp which must have slipped past me, to quickly to see it.

I was pretty pleased that the whole rather delicate exercise worked so well, fixing my tension problem without breaking the original part. Those things would be a bear to manufacture today, like the rest of the gun.

As I tinker with these Lugers, I ponder how truly amazing it is that the design was such a giant leap beyond the first generation semiautos, the C96 Broomhandle and Borchardt, and in such a short time span. Old Georg was a true genius, like his American contemporary, John Browning.

These guns are slick, strong, functional, handle great, and can digest the latest high power 9mm ammo...over 100 years after they were designed. That must be a record...as with the K98 action.

Phil, The trick to strawing is to cut the heat slightly before straw takes place. The ejector or any metal... acts like a heat sink. It will continue to absorb heat. I don't know the metalurgical process but I know how it does it in practical terms.

Since you cannot effectively stop the process you must turn off the heat before the straw takes place and let the straw appear as the metal attracts the last of the heat.

I have great success strawing or fire bluing with a plumbers torch and a fire brick. Gently wave a flame over the metal..patience is required. 450 degrees is quite cool as heating metal goes..it is important to heat evenly..never stop in one place. You can also pull the flame away let it cool and soak for a couple of degrees and continue to heat with no ill effects.

I suspect your problem with the toaster oven is the flashlight beam is likely yellow and you cannot accurately determine color with it. Perhaps an LED light might work better?

You can polish a nail and practice with a torch. Once you get the hang of it...it's a cinch. Just remember small parts are one thing..larger parts like a trigger are another. That takes even heat over a longer period of time and a toaster oven is probably better.

Jerry Burney

Phil, try stopping the heat with an oil bath once the color is reached, I hope I put that step in the sticky....anyway easer to get color and stop with oil then and guess work will we get the color if we stop before hand.......email me if I can help.

Jerry and PoliceLuger (Howard?),

Thanks to both of you for the detailed technical comments. I feed on those.

Since range testing has convinced me that I've got the ejector temper right, I'm going to quit while I'm ahead, despite the blue color. ...with this pistol and ejector, that is. :)

The fun I've had in fine tuning and shooting this S/42 over the last month or so has shown me the error of my way in only owning three Lugers. Original strawing is fine on the minty 1917 artillery and my 1930 Dutch Luger. But I expect to get my strawing technique worked out in the near future, on the inevitable "next one", as the little family expands.

Jerry, I was using a full size kitchen oven, not a toaster oven. And I guess this does not allow very precise temp control. Also, the tungsten bulb in the oven light certainly has its inherent color generation problems. I probably missed the color change.

In the past, I have always used your method of playing a low propane torch flame over a small part, to watch the color grow and flow. This time, I thought I would get more critical and uniform heat flow through the part by letting it heat slowly and evenly in an electric oven, as I do with my custom coil springs. I thought the heat would build more slowly, while I was watching it. Not true. So the color thing didn't work out, even though the tempering did.

Now I'm thinking more seriously about setting up what a close techy gun nut friend made for himself; a small electric heat treatment box, with glass window, controlled by a neat little transistorized keypad with LCD readout, and fed by a very accurate thermocouple. Control is within 25 degrees F or less. Amazing, to me. With this, I could experiment and come up with the exact color temp for a given part, and set the box to reach it and hold it precisely.

The real trick to getting a consistant and repeatable straw, fireblue or anything in between is to do it like they did back then. Brownells has some molten salt blue salts. They are a nitrate salt that is heated in an iron pot to a specific temp depending on the color desired. You can use a quality high temp thermometer to measure the temperature and by maintaining it consistantly you can insure that your straw doesn't go to blue while you try to get it cooled. The molten salt blue also has more consistant coloration because there is no contamination from various gasses or materials you might have in your oven, on your sand or in your heating device. Here is link to brownells page with the Nitreblue salts.
http://www.brownells.com/.aspx/pid=1...E_BLUING_SALTS

I have no affiliation with brownells other than as a user of their products. I've used this stuff for quite some time with good results. The only real warning I've got is don't let the salts cool with your parts in them. Its a pain to get the parts out of the solidified salts, you have to reheat. Quenching after dipping removes the salts so there is no real cleanup required

Hope that helps
Biff

Thanks to this article, I re-strawed an Erfurt mag catch/release. I didn't know what time frame was going to be involved, so I just pulled up my short stool in front of the kitchen oven and waited. It is a good thing that I live along, as not everyone would understand. I looked often, then realized that it was going to take a bit of time. Once I got the exact color that I wanted/needed, I applied a few drops of 3 in 1 oil to stop the process. I could not be more pleased. I just want to thank all of you folks that supplied this information, so I could accomplish the end product. Again, thank you.

So all you do is clean, polish, and heat the parts and they turn colors?

Yep, all the way from a light yellow up to a dark blue/black depending upon the temperature to which they are heated.