I got a question about marquenching and what it means. Basically Marquenching is taking a blade that is heated to above the critical point (somewhere around 1500f depending on the steel where it is converted from pearlite in to austite) and quickly cooling it (in either a low temp salt pot or in hot oil) to below the "nose" (a term comming from heat treating time/temerature charts) or to below approximately 900f in less than about 2 seconds. then holding it at around 400-500f until the entire blade is the same temperature. when the blade is removed from the hot oil it is very plastic and can be bent almost as easily as if it was 1500f. This allows the smith to straighten out any minor warps that occurred in the quench. As the blade cools the crystal structure of the steel changes from austite into martensite (the hardend steel) as the crystaline structure changes it creates a very faint high pitched ringing sound known as "singing". If the blade "sings" it means that the marquench was successful.
Here is a short video of the prosess: