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I think I recorded a positive pressure quench for the hollow grind video but it isn't available yet.
Most pp quenches specify 2atm which means roughly 30 psi of moving air. more than that is OK and I generally used 60 to 80 psi. I have a 12" long piece of tin nailed to the side of the work bench next to the quench tank. The tin curls into a cylinder shape about 5" in diameter. The nails are in the middle of the tin and the edges curl forward forming a cylinder, the edges are not connected - they are left with about a half inch gap.
Interrupt the oil quench when the steel hits about 1000 F. This doesn't take long, only a few seconds after the oil stops boiling around the blade. Put the blade inside the tin cylinder (I hang it on a nail in there) and start spraying the high pressure air on the blade using the gap in the tin to work up and down the blade. Have the edge of the blade facing the gap because that is the most important part to be cooled. Continue with the air until the steel is just warm to the touch of your bare fingers, then let it cool to room temp, then cryo immediately.....
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