Straw parts
 

I think Lugers with straw small parts are more attractive, why was it done? The straw finish is supposedly less effective than standard bluing; Did they not know? Was it just considered more attractive?

Why is a strawed metal surface less effective at preservation than rust or salt bluing?

Both have the object of replacing steel/iron surfaces with a hard oxidized magnetite surface. The strawed parts would be predicted to come in contact with fingers and finger oils more often than other surfaces of the Luger pistol.

I think that the strawing offers contrast and is more attractive. I'll have to check some references to see if there is an explanation as to why it was done.

After salt bluing was adopted in 1937, Mauser continued to make some commercial "Banner" toggle Lugers with strawed parts. I have one made in and dated 1938.

I believe your basic premise about "oxidized magnetite" is inaccurate.

The oxide formed from the temperature reached during straw coloring, is not the same as black oxide or rust blue.

I believe you will find that the straw color and the bright blue often seen are not related to cosmetic or "rust" treatment or prevention- but are the concurrent result of "drawing" heat treated and polished steel to achieve a particular hardness, flexibility, or to reduce internal stresses from prior heat treatment and forming.

In other words "straw" is not a primary objective, but a secondary effect of another action.
All the treatments you mention depend on proper care and application of oil , wax, or grease to prevent further oxidation.

That said, today the primary reason for "re" strawing is surely cosmetic. JMHO. :)

Well and truly said.

Mike, In addition to the above, strawing of the small parts took less time and work than rust bluing those parts. When Mauser decided to hot dip the lugers and P38s for the military, as they had several years exoerience with the PP series et al, it made sense to also hot dip the small parts. TH

Just to document for guys who are interested in the "protection" aspect of hot bluing, I'm posting this link to Brownell's "water displacing bluing oil".

Oiling of fresh from the blue and rinse tank blued parts is an integral part of the bluing process.
Clean and "unprotected" blued parts- i.e. those without an oil dip- will rust overnight. Don't ask me how I know this. ;)

https://www.brownells.com/gunsmith-t...-prod1086.aspx

The thread asks an excellent question. Don's comments make sense and suggest to me that they skipped rust bluing small parts as a cost saving measure; that's speculation by me.

When restoring WWII aircraft we often see a clear decision by the manufacturer to make small parts cheaply vs. durably. Restorers of vintage WWII aircraft love to gripe/observe that the aircraft were not built to last for decades, but rather to win a war (i.e.built for a single-digit service life). A flying WWII aircraft today often has less than 30% of its original parts by weight/parts count.

Don,

You probably found out the same way I did. HA!!!


Sieger

Yes, quite likely- but a lesson one never forgets.:thumbup:

A quick look at the paragraphs on "Tempering Colors" in this article:

https://en.wikipedia.org/wiki/Tempering_(metallurgy)

will confirm that the straw color (and others, depending on temperature) are the result of stable oxidation of the surface of the steel. These layers are more translucent on strawed steel and can proceed to darker blue with extended and higher temperature treatment.

One objective of such treatment is to prevent later formation of the rust form of iron oxide. I would expect that the tempering for hardness and brittleness of these parts was also necessary to prevent wear during the pistol's service life. Since both results can be achieved in one step this is likely a process advantage.

Did these parts remain tempered on later salt blued Lugers? And as this was likely, why were strawed parts not retained after 1937?

How was the salt bluing of these parts kept matching with the rest of the parts of the Luger that were not tempered?

"How was the salt bluing of these parts kept matching with the rest of the parts of the Luger that were not tempered?"

The minimal heat required for strawing would not/does not affect the color achieved in hot bluing.

The mfg. and heat treatment of many luger parts are detailed in the Mauser luger book, you can maybe find a more complete answer there as to the heat treatment if any by Mauser of these small parts.

There is a basic misunderstanding here. Straw (and fire blue) colors are not a finish, are not applied as a coating, and are not primarily intended to produce corrosion resistance.

The yellow and blue colors on small parts are by-products of the heat treatment of those small parts to attain a specific hardness to reduce abrasive wear without inducing brittleness.

Here is a link to a document that details that heat treatment process (historically called fire, or flame, heat treatment), and the temperatures at which specific colors appear (each color denoting a specific range of hardness):

http://navybmr.com/study%20material/...14250A_ch2.pdf

This heat treatment produced hardness has, as secondary and incidental effects, the production of attractive surface color and a very limited increase in resistance to surface corrosion. But this color and small increase in resistance to surface oxidation is just a by-product of the heat treatment done to reduce part wear due to abrasion.

To appreciate the range of colors produced by heat treatment one need look no further than the hold-opens on Imperial era Lugers, some of which display a spectrum of colors (see photo).
Krieghoff Lugers are frequently encountered with a mixture of yellow, orange and vivid blue small parts, likely a result of erratic temperature control.
Norm

My 1920 commercial exhibits the same range of colors on its holdopen (can’t post pictures of this since it’s at home and I’m up at school).

Norm,
that is a great picture, it shows on the one piece the range of temperatures reached on the hold open, from the bright polish to light yellow, straw, brown, red, purple, bright blue, peacock blue, and then into grey.:thumbup:

Many have seen the attachment below often posted before showing the colors and corresponding temperatures.

Kyrie,
Thanks for your post, I do hope it puts a stake through the heart of the misconception about "staw" and corrosion.:evilgrin:

Or could be a good example of selective heat treatment. Plant the rear of the part in a heat sink, flame harden and draw the front of the part, and the boundary between the protected/unprotected sections of the part can show as that heat gradient.