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Oyster Knife Blades
There are more than 100 different types of stainless steel. Both stainless and carbon steel are ordered in various parts of the world by special code-systems. Here are some examples: In the United States and a few other countries, the A.I.S.I. system is preferred. The Germans work with W.Nr. (Werkstoffnummer meaning industrial material number) and DIN numbers. Japan uses the J.I.S. coding system. Additionally there exists a U.N.S. (Unified Numbering System). For instance, the AISI code of an exquisite stainless steel alloy for oyster knives and many other types of cutlery is called 440 C. The Germans will reference that same code as W.Nr. 1.4125 and DIN X105CrMo17, while the Japanese will call it SUS 440 C. The UNS coding system will reference this type of stainless as S 44004.
Incidentally, those old stainless kitchen sinks that lucky scrap hauler brought in are interesting, because they are non-magnetic while all of our stainless oyster knives are very magnetic. Those sinks are made of so called austenitic stainless steel, a special group of stainless steel. The smart metal scrap dealer mentioned above might pay eight to ten times more (80 to 90c per pound on the US West Coast in Dec. 2006) for this type of stainless than he would for magnetic stainless. He may also consider some magnetic stainless grades as being no more valuable than common carbon steel - rated at perhaps just a few pennies per pound.
The stainless used in most quality American oyster knives (and many quality cutting knives) belongs in another very important steel group called ferritic stainless steel. It is very strong, durable, and highly corrosion resistant. As mentioned earlier, quality American oyster knives usually feature the AISI type 440 C. The "C" is important as there are other 440 grades (such as 440 A and 440 B, considered much inferior by many in the knife making process). There are also a few other, more exotic grades that are equal or superior to 440 C. There is yet a third important group that is called martensitic stainless steel. Like ferritic stainless, martensitic stainless is also magnetic, yet considered not as "good" as ferritic stainless. AISI 410 is famous in this martensitic group and is frequently used in the industry for applications such as corrosion resistant bins, plates, and liners. Hence, depending on the alloy ("metal mix") chosen and the way the steel is subsequently worked, many different grades of stainless steel can be produced, each with its own special characteristics. Knife manufacturers can subject a particular alloy to various heating, cooling, and beating (for tempering) techniques to further enhance its qualities. Among the other "ingredients", stainless steel also contains a small amount of carbon. Some knife-makers tout "high carbon" stainless steel, suggesting the best of both worlds: stainless, yet "tough as nails", much like a high quality traditional carbon steel knife. "High carbon" is a rather non-descript, unfixed measure which simply implies "extra hard and durable". However, this claim is frequently not some lame marketing gimmick, as higher carbon content can be most desirable and is not easily achieved in stainless. Chromium is one of the complicating factors. All of that chromium floating around in that hot stainless steel "soup" really loves carbon. This chemical affinity to carbon leads to absorption, oxidization and the precious chromium may end up going into the slag (slag or "scoria" is the refuse associated with the melting of metals).  Image above: The broader upper blank is a cheap stainless blank made in China (13 mm, 10 g). The more slender lower blank is a carbon steel blank once made by Carvel Hall (13.6 mm, 15 g). It is the blank that fits the famed Chesapeake stabber design (see gallery). Blanks made for use with wooden handles are commonly keyed near or at the end of the tang for a steel or yellow brass securing pin. Since stainless steel, regardless of the grade quality, is not a cheap material, it is also a great place for some manufacturers to start cutting corners. A cheaply made alloy will usually result in a poor blade that will bend like a "wet noodle" once exposed to a relatively small amount of torque. The tang, stashed away inside the oyster knife's handle, may end up being entirely inadequate to support the blade under heavy use - all to just save some of that semi-precious stainless steel on a large production run and turn out a nice looking "oyster knife" for the proverbial "five bucks" - and still carve out a healthy profit.
So what does the word "stainless"
really tell the "Joe Average" consumer much like me?
Not much unfortunately, as nobody can judge the quality of the
stainless steel a knife maker used by just looking at the blade
of an oyster knife (or any knife for that matter). Hence, when it comes down to the term stainless in knives, it all comes down to that really scary word in business and politics called "trust". Knowing who made that knife and where it was made certainly helps. I've resorted to only buying knives of any type from trusted names in the industry made in countries renowned for their knife steel quality. American, German, Japanese, French, Swiss, Swedish, and English knife makers have long held a high standing in terms of quality and these places of origin largely still hold great meaning. Care note: Never soak stainless steel blades in a bleach water solution, as it may irreparably stain and pit the metal. Hence, the chlorine content in public swimming pools for instance calls for a special type of stainless in those environments. Conventional carbon steel products (such as steel wool pads) should not be used to clean stainless, as they can introduce carbon steel rust stains. Abrasive kitchen powder cleaners should be avoided, particularly since they will dull the shiny finish of a fine blade. Some soap and hot water work best. * Carbon Steel Similar sentiments exist among many oyster industry professionals. Although the adductor muscle of an oyster is exceedingly strong, it cuts almost like butter. Hence, the edge of an oyster knife does not need to be sharper than a butter knife. Instead, a sleek blade with great strength and high durability, perfectly matched with a good handle, is of paramount importance. The so called stabber knives, for instance, feature narrow, flat blades which must be able to sustain a fair amount of prying and twisting torque - not just with one batch of oysters, but hundreds or even thousands. No stainless alloy will ever surpass a high quality carbon steel blade in performance along those lines. Most oystermen also don't care if the high carbon steel blade shows some staining after years of use. That oyster knife does not need to be pretty - no more than oysters need to win a beauty contest. The thought of salt water meeting carbon steel conjures up visions of rusty old boat trailers held together by little more than a prayer. The carbon steel alloys used in oyster knives don't "vaporize" into a pile of rust after a brush with salt water. On the contrary: I have a dozen different oyster knives of this steel genre, some aged 60 years or more, which have seen more than their fair share of use (and abuse) and no doubt still work every bit as well today as they did the day they were made. I choose to view the few stains they bear not as flaws, but rather as hard earned evidence of "good character". Old and trusted names in the American fish and shellfish knife industry, names like R. Murphy and Dexter-Russell for instance, feature a large selection of knives with stainless and carbon steel blades. For good reasons, some of their knives are only available in carbon steel.
Health advisory: There is a risk associated with consuming raw oysters or any raw animal protein. If you have chronic illness of the liver, stomach, or blood or have immune disorders, you are at greatest risk of illness from raw oysters and should eat oysters fully cooked. If you are unsure of your risk, you should consult your physician.
Advisements on any errors discovered are most welcome: Contact
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* Stainless Steel
Knowing
that these cryptic looking codes may designate some "good
stuff" might prompt us to open our kitchen drawers and take
a closer look at some of our "silverware" and the abundance
of other utensils marked "stainless". Unfortunately,
those mysterious codes are only rarely to be found. It really
gets interesting when we start waving a little magnet over all
those shiny utensils. Many will stick to it like glue while some
others will not respond at all.
"Rostfrei")
is the German designation for stainless steel. However, the term
Edelstahl alone does not necessarily qualify stainless
steel. It merely qualifies certain stainless and carbon steel
alloys as "noble" or "exquisite". Only by
adding the term Rostfrei (meaning free of rust)
is the Edelstahl alloy qualified as stainless steel.
In
terms of corrosion resistance, austenitic stainless is the best
stainless group of all. There are several types such as AISI
301, 302, 304, 309, 310 and others. 301 and 304 are common German
manufacturing choices for quality table forks, spoons and knives.
The respective formal code designations are X10CrNi18-8
and X5CrNi18-10 which are sometimes stamped or etched
in abbreviated form as simply 18/8 or 18/10. However,
the knives in such quality sets are quite special, as the manufacturers
will use the non-magnetic 18/8 or 18/10 on the handle part and
choose a magnetic stainless on the blade portion (pictured
above). The reason for this extra step in the manufacturing
process is that the austenitic group of stainless is simply not
tough enough to serve as a quality knife blade. Our "silverware"
drawer may also feature some eating utensils with colorful plastic
handles that were usually made in a few highly industrious nations
in the Far East. They are also marked "stainless",
are highly magnetic, usually comparatively light weight, and
much more affordably priced than the German counterparts. These
utensils frequently (not always) constitute the opposite end
of the stainless quality spectrum which some folks refer to as
"cheap junk". This rather harsh qualification may have
been brought about by easily bent spoons or the tines of some
of the forks that soon look like they desperately need an appointment
at the orthodontist. In the end, however, that delicious oyster
stew will taste just as good with a cheap spoon as it would with
an expensive one.
Inset
image: The pictured "oyster knife" originally looked
real nice at first glance. It was made in China and very low
priced when I purchased it new (cost me less than 5 bucks). The
handle seems to be made of some type of oak and is quite well
made. The tang locking pin is made of some brass alloy, also
acceptable. The blade is marked "stainless". However,
the horizontal inspection of the knife's blade revealed a very
slight wave and, in the plane of the handle, the blade was angled
downward just a tad. I checked the flex in the blade and it struck
me as quite high, particularly where it met the tang leading
into the handle. I then donned my shucking gloves and proceeded
to bend that blade down and around with much ease. As a layperson
in metallurgy I can only suspect that the grade of stainless
used was very inferior and the tang highly inadequate, thus nullifying
the rather acceptable quality value of the handle and pin alloy.
All stainless means is that the knife
blade will probably stay nice and shiny looking and hopefully
will not readily stain or rust - no more, no less. It will, however,
certainly stain and pit to some extent if improperly cared for.
I've also learned that carbon steel blades which naturally rust
are by no means necessarily "cheap junk" - no more
than cast iron pots and pans are to be quickly dismissed as antiquated
and inferior to those shiny stainless steel pots. In fact, certain
types of knives made of special high carbon steel alloys can
prove to be equal or superior to any stainless steel knife -
and incidentally, quite a number of food dishes will always taste
better when cooked in old-fashioned cast iron pots and pans rather
than their stainless counterparts.
Inset
image: Here's an "oyster knife" of unknown manufacturing
origin that looks acceptable at first glance, yet fails the quality
test. The handle is well formed in the classic pear shape and
the wood quality, aside from some stains, appears to be quite
good. The manufacturer added a hand guard. Oddly, it consists
of an oval piece of aluminum. Initially, the blade looked bright
and shiny, much like 
stainless
steel. In time, some rust spotting started to develop on the
ferrule and the blade. Soon, small flakes of what appears to
be some chrome or nickel plating started flaking off around the
tip. The subsequently exposed carbon steel underneath quickly
proved to be a highly corrosive grade.