Foil temp ratings vary by supplier on the same product. AFAIK, there are only two types - 321 and 309. I only use the 309. It is the higher temp version and works just fine on Elmax and beyond. You need to make envelopes out of the foil. Double fold the edge seams and press them down with something hard like a screwdriver handle. We use two envelopes, but you can likely get away with one. Some people put a bit of paper in the envelope or some powder to help reduce sticking of the foil to the blade. Both are controversial and the difference they make is likely small. FWIW, we do use a couple small pieces of paper to eat up oxygen in the envelope, except with Damascus. For Damascus and high temp, we normally use some talcum powder. Another controversy is whether to poke a tiny pinhole in the envelope. It is possible, with really good seams, for the air inside an envelope to expand and compromise the envelope seal. A pinhole lets you pick where a small leak would show up (usually the handle end) but then again, it guarantees a leak which you might not have had to deal with at all.
The whole idea of foil is to keep the hot blade away from air, so leave it in the foil while quenching it between thick plates. (Stays much cleaner and quench speed is more than adequate.)
The foil will make you bleed. :31: Keep band-aids handy.
