Oysters.us - Spat Perceptions Introduction

Oyster Knife Blades
John McCabe

The blade of an oyster knife must be straight and true, elegantly sleek, fairly thin and more or less narrow, so that it can slip between the shell halves of the oyster fortress and seek the adductor muscle without damaging the oyster's tender mantle flesh or organs. Since the delicate adductor muscle should be cut rather than torn, the blade's edge must be somewhat sharp. Simultaneously the blade must be capable of sustaining the torque caused by some prying and twisting and/or the punishment of chipping and chopping. Its tip sector, particularly the so called point, must be strong as an ox, yet as insidious as a rattlesnake. There are several blade designs which optimize the opening of an oyster when utilizing a particular opening method. Most designs are pictured and described in the gallery section of the introduction to oyster knives. The following text briefly discusses the steel types that are used and why (as well as those that are not - and why not). For a knife-maker, choosing and working the proper type of steel, be it stainless or carbon steel, goes a long way in solving the complex equation that ultimately adds up to a perfect oyster knife.

* Stainless Steel
Chefs and meat-cutters are not fooled by blanket terms like "stainless", because they know that the term covers many steel grades, everything from very good to very poor. The term "stainless" always managed to give me that fuzzy "quality feeling" for many years when purchasing various types of knives. I've since learned that the plain term "stainless" in itself is rather meaningless. In the cutlery industry the liberal use of this term has become very fashionable as a highly effective marketing buzz word that sells.

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.

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.

Instead of "stainless", some of our knives may stamped or chemically etched with terms like INOX or Edelstahl - Rostfrei. INOX is the abbreviation of the French term inoxydable meaning non-oxydizing. Edelstahl - Rostfrei (or simply "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.

Stainless steel contains a number of metallic alloying elements, most notably chromium (10% +) which imparts high resistance to heat and corrosion. Nickel (perhaps 8% +) is another important ingredient in stainless steel to balance the iron. Other metallic elements frequently used are molybdenum, selenium, titanium, columbium, manganese (sometimes used as a low cost substitute for nickel), and some others. The manufacturing process of stainless steel differs considerably from that of typical carbon steel. Comparatively, stainless steel is also rather valuable. A local scrap metal dealer will pay a guy with a big pick-up truck load full of old, dented up stainless steel kitchen sinks much more money than the next guy pulling up on the scales with a full load of rusty old bicycles, lawn mowers, and a couple of dead washers and dryers. Subsequently, the "stainless scrapper" might be having oysters on the half shell as an entrée before fixin' his dinner while the "carbon steel scrapper" will be lucky to receive enough money to refill the gas tank on his truck. However, if a bunch of rusty nails and brackets are still attached to those shiny old kitchen sinks, the shrewd scrap dealer will not be so pleased. He will classify the stainless load as "dirty" because of the attached carbon steel and will consequently pay considerably less than he would have for "clean stainless".

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.

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.

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.

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.

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). 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.

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
Carbon steel is very common. 90%+ of all the steel produced is considered carbon steel. Steel is essentially an alloy of iron and carbon, usually produced with the addition of varying amounts of other metallic element types. Some steels are commercially called irons although they may contain more carbon than conventional steels. On the other hand, wrought iron contains merely a few hundredths of one percent of carbon while most types of steel contain anywhere from .04% to 2.25% carbon. What makes many a carbon steel knife so very special is the particular alloy that was employed and the way it was fabricated. The proper alloy usually features a larger dose of molybdenum, vanadium, tungsten, or other metallic alloying elements than used in the production of conventional carbon steel alloys. The conventional types serve well for construction purposes, ships, paper clips, and countless other applications like "tin" cans (which consist of 99% low end hot- or cold-rolled carbon steel that was passed through a bath of molten tin).

High quality carbon steel oyster knives used to be the rule in the oyster industry. Carbon steel has been around for many centuries while stainless steel was first developed between 1903 and 1912. The immense value of stainless steel in countless applications was quickly recognized by many industries. In the decades to follow, the inherent expense and difficulty of producing stainless steel progressively diminished. The stainless alloys also became much stronger, thus making them also ideally suited for fine cutlery. By the 1960s and 70s, the naturally beautiful and easily cared for stainless steel products already ruled the cutlery industry and continue to do so today. Although stainless rules, it certainly does not rule absolutely. Given a choice, many chefs would never trade some of their high quality carbon steel knives for any stainless steel knife. Quality carbon steel knives are very hard and will hold a razor's edge for a long time, longer than most (if not all) stainless counterparts.

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.

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.

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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
© 2014 John W. McCabe