Joshua, Yes, as you mentioned, you would have to take a blade of known steel and compare the behavior of the blade after you quench and heat treat. If you have reason to believe it is a fast oil, you may test with a shallow hardening steel to see if indeed it is a fast oil. Using a shallow hardening steel , you should be able to actually see the hamon and know then without going through the entire heat treat. If it doesn't harden (no hamon) as it should on that blade, you could then quench a blade that is deeper hardening. You should be able to dial in the type and usefulness of that oil.

The above suggestion assumes that there will be further standard testing with files, cutting and grain structure tests.

Joshua, I would almost be willing to bet that you have a medium speed oil, industry really didn’t commonly work with the faster oils that bladesmiths like to find since industry's answer was simply to use a steel that could handle the heat treatment they had. To test it I would try one steel from the following list- 52100, 5160, 8670M, 80CRV, and another steel from this list- 1095, 1075, W1 or W2. Grind the two samples into wedge shapes like a flat ground knife blade, no need for the tip or tang work and then quench them both. Snap them and observe if the one from the second list (say 1095) snaps harder or deforms and breaks roughly near the spine.

Keeping things as wet and cool as possible grind a broken end smooth and etch it in ferric chloride or strong vinegar. This will reveal the transition from martensite to pearlite and on the steel from list 1 there shouldn’t be a clear transition, but in the steel from list two there may be. The nearer the transition is to the spine the greater the chances that you have a faster oil. Most oils will begin to peter out at around 3/16” in the steels from the second group. A good fast oil may push the pearlite up to or above ¼”, a medium speed most likely will not.

Of course, if you have access to a hardness tester then you can get even more definitive results by grinding that wedge into a single sided stepped wedge, increasing each step thickness by 1/16” and then doing hardness tests on each step. When I am involved with quenchant development projects I cross-section the wedge and do hardness tests every mm up the inside face and accompany it with metallography, but you can get there without that level of trouble.

Grain size and structure will be irrelevant to the quenchant as it is determined by the austenitizing heat not the quenchant. What most folks think is grain structure/size differences on fractured end grain is actually differing modes of fracture from martensite to pearlite. Since there is slip and deformation involved with pearlite fracturing it will look rough compared to the clean brittle break of martensite.

Thank you both for the rapid and informative responses.

Lin, as luck would have it, I not only have some W-1 in the shop, I have a knife blank I recently forged to shape from some of it. I don't particularly like the way it turned out either, so it's a perfect candidate!

Kevin I have a couple of questions:

"observe if the one from the second list (say 1095) snaps harder or deforms and breaks roughly near the spine" if it does, what does that tell me? I think it tells me it's a faster quench,(providing the spine is 3/16 or greater in cross section)is that correct? If it doesn't, what does that tell me? (I assume the reverse)

I might have a piece of 5160 hiding somewhere in the shop, but I don't have any of the other ones on list 1. I do have ample supply of O-1, which I think is pretty close to 52100. I assume O-1 will suffice for a list 1 candidate, yes?

As quenched, steel should be brittle if it is fully hardened and thus you should not get bending or toughness out the fully hardened blade when snapping it. The first group is really more just a control group to see what a fully hardened blade from a medium speed oil is like. O-1 will work but it will not give you much of an idea of degrees of speed within the medium speed category because it is so deep hardening that just about any oil will harden it quite well.

"O-1 will work but it will not give you much of an idea of degrees of speed within the medium speed category because it is so deep hardening that just about any oil will harden it quite well."

Well that's good news, because it's my preferred HC steel for forging! So the oil should be good for most of my regular knives.

So, without seeming too thick, I think what you are telling me is this:

Take two rough ground wedges (5160, W-1), quench as normal and check for the Hamon on the W-1. Hamon-yes, I have a fast oil. Hamon-no I need to break the wedges and do the grind & acid test to see how fast the oil is. The closer to the thicker cross section the transition is from M-site to P-lite, the faster the oil is.

No matter what, The oil will work for most simple deep hardening steels, but I will need something more toward the fast end for complex or stainless varieties.

Did I get that right?

Hamons are a result of incomplete hardening so the presence of one, in the absence of any clay, will most likely indicate that the oil is too slow for the steel. The oil should work fine for O-1, L6, 52100, 5160, 8670M, 80CRV etc… You will need a fast oil for 1075, 1080, 1084, 1095, W1 and W2. Generally the more alloying, the slower the oil you will need, the simpler the steel the faster the oil needs to be.