[exbiologist]

I was looking through the Brownell's catalog and didn't see any solutions for straw coloring. Is this still done?

[rcmodel]

Very rarely.

It was never done just for the finish anyway.
It was just a result of the heat treating/tempering process used to harden certain parts.

rc

[exbiologist]

I'm familiar with case coloring, but I thought this was different. Saw a video where the extractor and strker and inside of a cartridge trap were done with this and thought it looked good. I was under the impression that it was done with a different chemical when rust bluing.

[rcmodel]

Perhaps it is today, as they use chemical color case-hardening too.
But not for hardening as intended.
Just to make reproduction guns look like the old guns with case-hardened frames looked..

Straw color, as used on P08 Luger parts, and other guns of the day?
It was a result of the hardening/tempering of the part.

Steel is hardened by heating it cherry red, then quenching it in water, oil, or brine.
That makes it glass hard and very brittle.

Drawing the temper at 450 or 460 degrees results in the polished part turning a light or deep straw color and giving a hardness suitable for triggers, sears, safety's, firing pins, etc.

Going up in temperature results in various shades of blue, with the darker the blue being progressivly softer.

rc

[exbiologist]

I found it now, it uses the same chemicals as nitre bluing, but produces the straw color at a lower temperature.

[rcmodel]

The process still requires to nitre salts to be melted at a temp of 570° F. - 650° F then the part immersed in the molten salts until the color change takes place.

This is well above the temp used to draw the temper on most gun parts that actually do anything.

It could be used on non-stressed parts like screws, trigger guards, barrel bands, sight bases, & such.
But never on parts that have to be heat-treated for strength. (Like frames, triggers, hammers, flat springs, etc.)

The old time manufactures did it because they knew exactly what grade steel they were dealing with, and how to temper & draw it in molten nitre salts.

The home DIY'er hasn't got a clue what steel or temper he is dealing with on already heat-treated critical gun parts..

rc

[Oyeboten]

The Molten Salts in and of themselves, only transmit heat, and, exclude Oxygen...they do not impart any Color to the item being heated in them by immersion.


Straw Colors - for a super 'clean' piece of Steel, whether hardened or not, can be obtained by heating, and, heating fairly slowly and evenly is best...ideally in a reduction Flame ( to exclude as much ambient Oxygen as possible) or other Oxygen excluding manner, and watching carefully in low ambient light...removing from Heat and, usually, quenching soon as the desired color is beginning...time lag from heat to quench, can be enough for the next color to arrive, thus loosing the color one was after.


Same with 'Blue'...

But...again the "Caution" - As rcmodel mentions, Steel which has been previously Tempered to a specific hardness/toughness for it's application, could have it's Temper compromised or inadvertently re-done to a differing hardness/toughness by being re-heated uncritically in an attempt to acheive certain colors, also, the traditional Molten Salts are too hot for Straw to be easily accomplished, since you'd have to catch it as it is quickly passing, or, rather, just as it is almost arriving.

With practice, probably one could...but it'd be tricky.

[navyretired 1]

Straw color is best done in molten nitre but can be done with a torch. The part must be polished after hardening them heated slowly to the right staw color then stopped. I use ice water. But about the only straw colors I do now are Lugers which are a lot of work. Straw wasn't used as color contrast but was the actual drawing temp desired for a tough and not brittle part. You will never see a luger strawed part that is battered or burred most GS just blue the straw parts but it's not that tough to arrive at a nice straw finish on the 2 or 3 parts necessary.