This thread seems like an appropriate place to ask a question that I have wanted to ask for a very long time. I bought five gallons of CLC Quench K 186. I bought it because I really didn't know any thing at all about quenchants (I still don't). All I knew was that I thought that I wanted a fast oil. I called and talked to the guy who OWNS the cotton pickin' company and explained what I wanted. He sent me this stuff. It seems to me like it works just fine but I really don't know. The technical data sheet that I received with the oil said that its quench speed is 190 ft/sec. How does that equate to 9 seconds? I have read a lot of material about quenchants so I know a lot of stuff about what is supposed to go on down at the atomic level and all of that but I can't see them liddle buggers. My O1, 15n20 and 1095 blades skate a file, they take and hold an edge, they flex over a brass rod. I looked at Kevin's micro-graphs on this thread and I have just got to wonder how do you ever really KNOW if what you are doing is the best that can be done. I can tell you one thing - the guy at CLC is a nice guy who was very helpful to some fool out in Oregon wanting to buy five gallons of oil that he normally sold by the tanker truck load. Thanks guys. Nicholas