Thread: Method to test stone's finish?

Not the Barber! The stone!

Sediments from standing water settle biggest first then the smallest. I was just thinking if you took the slurry for two stones and added them to two small glasses of water, which ever settles last maybe the finest finisher. I know this is a crazy hypothesis, but i think it could work with some comparison/experimentation. But some of these grit sizes may take years to settle. And i don't know how the binder in synthetic stones could effect this.

My method consists of wetting the surface of a stone and then rubbing it with my fingers with a decent amount of pressure. It helps if the stones you're comparing it to have been lapped to the same grit. It's not accurate but it gives a decent indication about fineness and cutting power (more resistance).

It doesn't work that well for comparing 2 completely different stones like a soft Thuringian versus a hard CF. However if I line up all my stones of the same kind e.g. Coticules or Thuringians I have no trouble picking out the finest and the coarsest.

Originally Posted by Vasilis

The smoothness of a blade on our face also depends from the steel and its hardness. You can try shaving with an authentic yanagiba, but, no matter the way you hone it, something harder than 60-62HRC will not give you a smooth shave.

Have you shaved with razors beyond 60 HRC. ? I have & my experience is contrary to yours. The fineness of the steel grain has a greater influence on smoothness but even then something like coarse grained stainless can still be honed to be comfortable.

Originally Posted by Johnus

Not the Barber! The stone!

I meant the stone the alternative goes without saying.

Seriously my stubbled cheek seems to be working well enough. The difference between rubbing the Norton 8k and the hone on my face is quite evident. The hone cuts faster than the Norton but that is a different parameter.

The only knife I would even contemplate attempting a shave with would be a very hard, and small honyaki usuba with a straight edge, anything else you would have to factor in awkwardness.

Originally Posted by onimaru55

Have you shaved with razors beyond 60 HRC. ? I have & my experience is contrary to yours. The fineness of the steel grain has a greater influence on smoothness but even then something like coarse grained stainless can still be honed to be comfortable.

It's also the steel as I previously wrote. Was it a stainless, just high carbon, HSS, tamahagane? For he vanadium or molybdenum containing alloys, it can be honed to a smooth finish. For high carbon, high chromium content, the coarse grained ones, it is difficult, since you say it's not almost impossible. But finish them in the same stone, and compare how smooth they get, I don't think you will disagree that there will be difference. And of course, anything softer than, I'm not sure, 45HRC? can't shave. And, yes, it was awkward.

The slurry in the glass of water does sound clever and it's already used for testing the soil for sand and clay content. But the difference in density of the abrasive particles could give false results. I think I'll try it.

See how it scratches a larger piece of metal, like a piece of flat or bar stock. Rub the same piece of metal over both hones, then compare side by side. That would make for a larger "canvas" to view the scratches made by the hone. This may not be helpful in determining how a razor shaves but it would tell you something about the hone. If you decide to try it please take pics and post too.

Michael

Originally Posted by jaswarb

Is there some method to test stones against one another to determine which will finish smoother?

The obvious answer is to hone and shave with them both but is there a more direct less subjective method to limit the variables which doesn't involve electron microscopy? My honing skills haven't developed well enough to be eliminated as a variable.

I would like to determine if my HSB & CO OVB is adequate as a finisher. I have a Norton 8k and sometimes I will finish with a few strops on a crox paddle.

What do you think of having a stone testing guy/gal, someone who anyone could send a stone to, sort of like the guy who stamps Aichi nagura. Just one person who would use his/her empirical judgment and stamp the stone. A person of impeccable standards who would get paid per piece to test the stone to suit their (at some point prefessional) standards. It should not be someone like myself who would obviously have an alterior motive, also those ruled out might be someone who buys only or tests only stones currently from one source. I think it would even be cool is the community paid for some training of this person.

I could imagine a retired person, someone who displays restraint and is prudent, a wise person. At $2 or $3 or $5 a pop it would be worth it to the owner and to the tester. Alx

Well I am at present experimenting with a bar of Nickel Silver. It is capable of taking a very high shine. I am rubbing it with several different grinding medias and looking under the microscope at the results.

If I can get better quality micro photos I will post them here in a day or so.