I've also tried this to no avail. Im using Heinz vinegar, but it's not the "unfiltered" kind, dont know if it matters. I bring the vinegar to a rolling boil, as hot as can be steam everywhere stinking up the house type boil. And I keep the knife right by the pan so the vinegar is still hot as hell when i wipe it, and ill wipe over and over for 20 minutes.. Just a few random greyish sports and some orange discoloration. I cleaned the blade thoroughly with alcohol too and wore gloves. What gives?
Instead of just wiping the hot vinegar on the blade, try dipping the blade into the hot vinegar and WATCH IT CLOSELY. If it's 1095 steel, it'll start to BLACKEN very fast (in seconds); you might even see bubbles coming off the steel and rising to the top. Lift the blade out of the vinegar, and you'll see it continue to darken before your eyes, as the exposure to air accelerates the reaction. Might also see some red rust begin to form.
If the blade isn't 1095, but instead stainless (usually 440A on the older USA Schrades, if stainless), it won't discolor much, if at all, using the method above.
If you're boiling pure vinegar, be careful with the above. I used a mix of 1 part vinegar to 2 parts water, heated to ~180°F (used to de-scale my coffee maker first) when patinating my Schrade 8OT's clip blade. A weaker dilution, but still worked very fast, as I described; the heat is what really speeds it up. With pure vinegar, boiled and with no added water, it'll be much more aggressive.
If your blade does blacken and/or rust quickly, clean it up using a paste of baking soda and water, scrubbing until no red/brown/black discoloration is coming off the blade anymore. The baking soda will neutralize the acidic reaction (most important) and scrub off any loosely-bound oxide (red rust and some of the black). Then wash/rinse/dry everything thoroughly, and lube the joints.
David
