Post by Christopher on Aug 23, 2004 20:55:43 GMT 12.75
Different metals require different finishes. What works for one won't be the best for another, and all of your options have their pros and cons.
Mild Steel (the stuff you get from Home Depot)
Only called steel because there's a little carbon in it, otherwise mostly iron and some impurities. Rusts quickly, and left in the weather, a 1/4 inch bar will get nasty and brittle within a couple years. Because of the rolled nature of it, even when forged it posesses a very homogenous surface, which moisture seems to love.
Cast Iron (the stuff of good dutch ovens)
CI starts off as a puddle of iron with about 4% carbon, or four times as much as a good "high carbon" knife. The problem is, at this level, the carbon clumps together into chunks, leaving a rather brittle and "granular" materieal to work with - unforgable (crumbles at heat), and difficult to grind well. Most CI products are cast with a texture to them, which is what allows "seasoning" to work - the rough surface allows the stuff you cook onto it to grab and form a protective barrier against moisture and corrosion. The key here is to use something that will remain foodsafe, and here most vegetable-based oils will work nicely. Bring to a good heat (400+) and add oil liberally over the surface, and let it smoke for a while. This burns the oil at the surface, forming a protective glaze on the metal.
Wrought Iron
Real WI is a product of melting iron, similar to CI, but with little or no carbon, and a healthy dose of silica slag. Wrought Iron will form a light surface rust, but the quantity of silica prevents further corrosion, leaving you with a long-lasting material. As with all metals, paint helps, but a natural finish of a light rusting that's occasional burnished with steel wool is a nice one that looks old but remains very durable.
Carbon Steel
The stuff of good knives (not counting stainless steel), "high carbon" in cutlery is around 1% carbon to 99% iron, by weight. This stuff can be heat treated and controlled through several different crystaline phases. Hard=brittle, soft=durable; the best knives combine these properties where needed. I say knives, because there are few other applications where high carbon steel is appropriate. Spring steel is a close cousin, with around 0.6% carbon. Most importantly, this stuff will rust quickly. The best protection is a mild oxidation layer, often achieved by "etching". Mirror finishes remove many of the opportunities for water trapping, but eventually even these will succumb, as surface contaminants (finger oils, even) trap moisture and breed rust.
Mild Steel (the stuff you get from Home Depot)
Only called steel because there's a little carbon in it, otherwise mostly iron and some impurities. Rusts quickly, and left in the weather, a 1/4 inch bar will get nasty and brittle within a couple years. Because of the rolled nature of it, even when forged it posesses a very homogenous surface, which moisture seems to love.
Cast Iron (the stuff of good dutch ovens)
CI starts off as a puddle of iron with about 4% carbon, or four times as much as a good "high carbon" knife. The problem is, at this level, the carbon clumps together into chunks, leaving a rather brittle and "granular" materieal to work with - unforgable (crumbles at heat), and difficult to grind well. Most CI products are cast with a texture to them, which is what allows "seasoning" to work - the rough surface allows the stuff you cook onto it to grab and form a protective barrier against moisture and corrosion. The key here is to use something that will remain foodsafe, and here most vegetable-based oils will work nicely. Bring to a good heat (400+) and add oil liberally over the surface, and let it smoke for a while. This burns the oil at the surface, forming a protective glaze on the metal.
Wrought Iron
Real WI is a product of melting iron, similar to CI, but with little or no carbon, and a healthy dose of silica slag. Wrought Iron will form a light surface rust, but the quantity of silica prevents further corrosion, leaving you with a long-lasting material. As with all metals, paint helps, but a natural finish of a light rusting that's occasional burnished with steel wool is a nice one that looks old but remains very durable.
Carbon Steel
The stuff of good knives (not counting stainless steel), "high carbon" in cutlery is around 1% carbon to 99% iron, by weight. This stuff can be heat treated and controlled through several different crystaline phases. Hard=brittle, soft=durable; the best knives combine these properties where needed. I say knives, because there are few other applications where high carbon steel is appropriate. Spring steel is a close cousin, with around 0.6% carbon. Most importantly, this stuff will rust quickly. The best protection is a mild oxidation layer, often achieved by "etching". Mirror finishes remove many of the opportunities for water trapping, but eventually even these will succumb, as surface contaminants (finger oils, even) trap moisture and breed rust.