[Crex]

We used to do the brass brush trick when doing blacksmithing demos. Was kind of a pseudo-alchemy joke. We'd forge out an object like a leaf or candle holder, ask some little towhead in the crowd if he had "majic" breath that can turn black steel into gold then have him blow on the object before putting it back in the forge. When pulled back out for the final descale brushing, switch from the steel brush to the brass brush (slight of hand), and whala steel to gold! Kids love it and really messes with some adults as well.
Never did it on a knife blade, as always concerned about final temper, but straight out of temper oven (with some steels) sounds good.....thanks for the tip Jim.