description of the term straw

[Kyrie]

Originally Posted by Kyrie

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Case hardening produces, at the quench, surface colors. These colors are usually just muddy brown or grey, but it was discovered the addition of different elements to the material used in the case during surface carbonization would produce different colors - some of those colors were just stunning.

These colors produced at the quench would quickly just fade to muddy brown/grey, and people worked to find a way to fix the colors so they did not change. That effort was successful, and "case colors" were born.

The production of different colors at the quench became (and still is) something of an art form, with the specific materials added to the pace being a closely held secret. Companies that provided case hardening services were commonly located close to slaughter houses, as animal bone was one of the major components of the pack. Things added to the pack to produce colors like green, yellow, and royal blues included some passing strange things, including salts produced from urine.
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Let’s do some pictures.

Taking advantage of the need to do surface hardening by case heat treatment to produce beautiful case colors is an art form. I suspect that art form reached its peak in the production of artisanal side lock shotguns.

What follows are some pictures of the colors that were produced by master Spanish shotgun makers, as the case hardened the lock plates of Spanish side lock shotguns.



Here is a close-up:



The uninitiated will sometimes mistake these case colors for a kind of bluing; they aren’t. These case colors were produced at the instant that the newly hardened lock plates were dumped from the heating case into water to quench the surface carbonized lock plate.

The temperatures at which surface carbonization is attained will frequently warp the lock plates, and the warped lock plates must be beaten back into proper shape. Remember the earlier discussion on leaving the interior steel soft so the part can endure repeated shocks without shattering? This reshaping of warped lock plates is an example of what that soft center makes possible. If the locks were hardened through and through, they would shatter rather than reform back into the proper shape.

Here are a couple more examples of case color:

From an Astra side lock 12 gauge:


From a Gregorio San Martin 20 gauge side lock:



Case colors, like the heat straw colors, wear fast and disappear with handling. Here is an example:



Many, many shotgun people don’t understand the nature and origin of case colors and suppose case colors to be a finish, like bluing. It’s not unusual for these folks to ask about the restoration or re-coloring of case colors. That’s made faking case colors into something of a village industry.

Indeed, the ability of gun makers to produce attractive case colors at the end of the case hardening process is a dying art, and lower priced shotguns frequently are produced with (relatively) cheaply done fake case colors that are produced chemically. Here is an example of a lock that had fake case colors applied: