Acer S. recently wrote something like "Who cut the files . . . made the gravers?"
Brought to mind an old recipe for hardening files. Would make a file every bit as good as Nicholson did in the USA, until Our Gov't got into the act. US Gov't prohibited use of that nasty potassium ferrocyanide in heat treat. This is a chemical currently used to prevent caking in Sea Salt for the food we eat. Ya can eat the stuff but not heat treat with it. Can you say "Kasenit"? No, not anymore you can't.
So here is the recipes for files, and for gravers, from Sources for the History of the Science of Steel 1532 - 1786, Cyril Stanley Smith.
"The Thirteenth Book of Natural Magick, 1589, by G.B. Della Porta:
Chap. IV.
How, for all mixtures, Iron may be tempered most hard
Now I will shew some ways whereby Iron may be made extream hard: for that Iron that must be used for an Instrument to hammer, and polish, and fit other Iron, must be much harder then that.
The temper of Iron for Files.
It must be made of the best Steel, and excellently tempered, that it may polish, anf fit other Iron as it should be: Take Ox hoofs, and put them into an Oven to dry, that they may be powdered fine; mingle well one part of this with as much common Salt, beaten Glass, and Chimney-soot, and beat them together, and lay them up for your use in a wooden Vessel hanging in the smoak; for the salt will melt with any moisture of the place or Air. The powder being prepared, make your iron like to a file; then cut it chequerwise, and crossways, with a sharp edged tool: having made the iron tender and soft, as I said, then make an iron chest fit to lay up your files in, and put them into it, strewing on the powder by course, that they may be covered all over: then put on the cover, and lute well the chinks with clay and straw, that the smoak of the powder may not breath out; and then lay a heap of burning coals all over it, that it may be red-hot about an hour: when you think the powder to be burnt and consumed, take the chest out from the coals with iron pinchers, and plunge the files into very cold water, and so they will become extream hard. This is the usual temper for files; for we fear not if the files should be wrested by cold waters."
This four-centuries old process is entirely correct, by current metallurgical knowledge. The chimney soot, of course, is a nearly pure source of carbon to carburize or case harden the surface. “Ox hoofs”, provide nitrogen as well. Nitrogen, along with the carbon, further improves sliding wear resistance. Salt and glass melt the whole mess together to provide intimate contact with the surface, and “activate” the surface to make it easier for the iron to absorb carbon. This is really 21st Century stuff! Even today the “usual temper for files” is just as they come from the quench, with no further reheat/temper/draw.
also -
"A Tool made to cut Iron.
When the same red Rose colour appears, plunge it into the water, or some sharp liquor that we shall shew; and you must obsrve the second yellow colour, or wheat color, and then csst it into the water. There are the best."
I think that 'second yellow colour" was the temper color. We use the term "straw" color.
Until recent years when our EPA helped protect us, Nicholson file practice was to coat the just-cut high carbon steel files with a roughly similar mixture before hardening from a protective molten lead (now bismuth) bath. The modern version of “Ox Hoofs” is potassium ferrocyanide, K4Fe(CN)6. It provides nitrogen, great for sliding wear, along with carbon. This was mixed with flour and bone black, and all were boiled together in salt water. They used to call the stuff "cyanide loaf", a truly frightening name.
Guess I should make it clear "FERROCYANIDE" is not especially poisonous. Still, it might be best not to make sandwiches using your cyanide loaf.
My grandsons' Mom reads product labels & was quick to point out that same chemical on a can of Kroger's Sea Salt. To the trash, now.
No, I do not know whether the gunsmith himself or some special Filemaker Guild did this work in '89.
