Thread: Another whats under the stone post.

Received this 2nd hand natural sharpening stone from the U.K this morning.

Under all that old oil and grime there are features that indicate its most likely crystaline novaculite in structure, an oil stone, either Washita or Arkansas.



The same stone after being flattened reveals much more of the stones natural features.



During the flattening process, indications are, its a hard stone, slow slurry releasing, most likely pointing to its identity as being Arkansas.

To validate that fact, requires some mathematics to work out the stones specific gravity. (SG)

Weight of the stone = 515 grams.

Mass ( 20.1 cm x 4.7cm x 2.3cm) = 217.28 cm3

515/ 217.28 = 2.37 g/cm3

SG = 2.37.

Using the following site as a reference; http://www.danswhetstone.com/stone_grades_101.htm,

It identifies the stone as being within the Hard Arkansas range of 2.30 - 2.45 SG / 800 - 1000 grit.

StewieS;

Should be an excellent finisher/polisher. I have a translucent Arkansas that I use occasionally after the Select Coticule for a little more polish and smoothness.

Washita

Sent from my SAMSUNG-SM-G935A using Tapatalk

Give it a hose of Oven Cleaner, a scrubbing with a scotch brite and a Simple Green bath and you will have a very good idea of what it really is.

If it’s an Ark, put a razor on it before you lap it, it may have a hundred-year old burnished finish on it, that will put a nice edge on a razor, who knows, next time...

If you want to get all the oil out, Simple Green and water and a good soak, I have soaked Arks for up to a year, to get an old Lilly White pristine and clean smelling.

Lately I have been using 99 Cent Store “Awsome” on some stones with better results than Simple Green for soaking. Glass Pasta jars with the clamp on lids and rubber gaskets, from the thrift store, work well to keep the air out, change the water and degreaser every couple weeks, until they stop releasing black oil.

Nice find, should be a good bevel setter or tool hone.

Originally Posted by aaron1234

Washita

Sent from my SAMSUNG-SM-G935A using Tapatalk

aaron; I am prepared to listen. Put forward your case that the stone is not an Ark, but a Washita.

StewieS.

Also looks like many grimy washita stones that I have cleaned up. I'm not close to as knowledgeable as the folks here though.

I have a Washita that is similarly colored. Great stone for me.

Stewie may be right in this case. The volume (not mass, as he inadvertently labeled it) of the stone if it's a Hard Ark or Washita would be less than his calculated volume, because Hard Arks and Washitas are somewhat porous (not to mention any missing volume due to chamfers, corner rounding etc). Less volume means the density would actually be slightly higher than his calculated density. Thusly it would pretty much have to be a Hard Ark if it's really from the Ark family of stones.

Had the opportunity to test this stone out to form a secondary bevel on 1 of my workshop chisels. The stone itself retained a good level of oil on the top surface of the stone, and there was no need to add further oil while working the stone. Fairly impressive given its a rather hot day outside, and a few degrees hotter within the workshop. The stone is a very slow release stone, with little sign of slurry release. The top surface of the stone is what I classify as hard to very hard. As noted within my opening post, using the ANSI Standard, based it suggests the range of grit at 800 - 1000. I have some slight concerns with how the ANSI and JSI Standards vary greatly from that being stated by a lot of natural stone suppliers. Japanese nat stones being a relevant example. Based on what is being declared by these Japanese nat stone suppliers, I would rate this stone equivalent to 8000 grit. This is to large extent based on the level of sheen left on the steel after being worked by the stone. The finer the scratches, the higher the grit, the change in sheen to reflective shine. Some alloy steels such as A2 and PM may vary slightly from this principle. Moving on to the photo's, the 1st photo shows the secondary bevel after being worked by the stone. The 2nd photo shows both the primary and secondary bevels after a dozen strokes on the pure chromium oxide impregnated leather stropping block. The end result is a very sharp cutting edge.

regards StewieS;

Of interest, if I were to reduce the total weight of this stone by 25g (4.8% of its current weight), it would still be borderline high of a Washita's range of SG. (2.25 or under)

StewieS;