Ken Shepard wrote:
> The various grades of Arkansas stone are determined by specific gravity.
>   The density standards for Arkansas stones are as follows:
>
> Soft Arkansas (Washita)      2.20 - 2.30
> Hard Arkansas     2.30 - 2.50
> True Hard Arkansas, Black Arkansas, Translucent   2.50+

Phil Schempf wrote:
 > This outfit has a write-up that may shed some light on the subject or add
 > some fuel to the flames-
 >
 > http://www.danswhetstone.com/stone_grades_101.htm

I've had some private emails saying my stone looks a lot
like a Norton No 1 Washita,

I had some fun last night attempting to measure
the SG of my stone. There are various methods
proposed on the web;

The commonest one, aimed at 10-12 year olds,
measures the weight of the item, and then measures
the volume by dunking the item in a container full of water,
and measuring the overflow. This gives mass/volume.

Next commonest is to "weigh in air" / "weigh in water"
method, which is easy if you have a spring balance, harder
if you have a beam balance, and REALLY hard if you
have a digital scale.

The rarest is the weigh in air, weigh by displacement.
For the second weight,  you need a container of water on your scale,
into which you dangle the item; the extra weight pushed down
onto the scale by the water being displaced is the figure you need.

The SG is then (simply) weight in air divided by weight displaced.

In the case of my sharpening stone, I used a lasagna tray,
but a loaf tin, meat load tin or terrine would all serve.

The upshot was - the SG of my stone is somewhere between
2.27 - 2.39 (allowing for 5g error on my scale).

This puts it at the boundary of the Washita/Soft Arkansas
categories which is what we knew already; still,
confirmation is nice.

Still - I got to revisit my high school physics days, which is
always a blast.

BugBear
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