The specific gravity collection

[Legion]

Today I had a bit of time so I thought I’d measure the specific gravity of a few of my natural hones.

First I tried a washita and a trans Arkansas. They came in at 2.24 and 2.65, so no real surprises there.

But next I did my Lynn Idwal, also novaculite, and that was 2.74!

And then a Glanrafon, a slate, but more hard and novaculite feeling than any other slate i’ve come across, 2.82!!!

Those two surprised me, but not really after lapping them.


What other types of stone do we want to add?

 

[rbscebu]

My balsa strops come in at 0.60. Does that count?

 

[cotedupy]

I'll add some various things to this thread once I've re-measured them properly in water. But this is worth remembering / pointing out to anyone who comes across this but doesn't know about SG...

Specific Gravity is a measure of density, which based on weight. It does not correlate with hardness across different types of stone. A Coticule for instance might have a SG of 3.0, but is far softer than a Translucent Arkansas with a SG of 2.65, because they're made from different things.

Specific Gravity is most useful as a measurement when comparing two stones of the same type.

 

[Legion]

I'll add some various things to this thread once I've re-measured them properly in water. But this is worth remembering / pointing out to anyone who comes across this but doesn't know about SG...

Specific Gravity is a measure of density, which based on weight. It does not correlate with hardness across different types of stone. A Coticule for instance might have a SG of 3.0, but is far softer than a Translucent Arkansas with a SG of 2.65, because they're made from different things.

Specific Gravity is most useful as a measurement when comparing two stones of the same type.

True this.

Speaking of coticules, that is one stone I would be interested in comparing the different veins. But since almost all mine are in some way at least 50% BBW or slate, pretty tricky to measure.

But I think where things might get interesting is where they are supposed to be more or less the same, but then not. Like, why is my LI so much heavier than a trans Ark? They are both novaculite, what is different?

And also, there seem to be a couple of stones that are visually different that we call Lynn Idwal. Let’s get a few measurements to compare. Same with Yellow Lake, etc.

 

[David]

My balsa strops come in at 0.60. Does that count?

He's talking about specific gravity, not mojo levels.

 

[Bowmaker]

I'll add some various things to this thread once I've re-measured them properly in water. But this is worth remembering / pointing out to anyone who comes across this but doesn't know about SG...

Specific Gravity is a measure of density, which based on weight. It does not correlate with hardness across different types of stone. A Coticule for instance might have a SG of 3.0, but is far softer than a Translucent Arkansas with a SG of 2.65, because they're made from different things.

Specific Gravity is most useful as a measurement when comparing two stones of the same type.

SPG will also mirror the absorption or porosity within like stones. Probably doesn't give use the full story on some of the soft arks that have inconsistent surfaces.

 

[Bowmaker]

My balsa strops come in at 0.60. Does that count?

Only when I go fishing....

 

[FarmerTan]

As a nurse I often used to measure specific gravity of urine.

I did measure my kidney stones a few times. They actually weigh MORE than a Meteor as they pass through a ureter.

True story doggone!

 

[eKretz]

But I think where things might get interesting is where they are supposed to be more or less the same, but then not. Like, why is my LI so much heavier than a trans Ark? They are both novaculite, what is different?

Purity is what is different. Quality Arks are well known to be composed of nearly 100% pure silica and have little to no air/gaps in the stone. The high end stones are very nearly uniform in their density. Not so for any other stones containing novaculite. Impurities can be either more or less dense.

 

[cotedupy]

Welsh Green Stones

Llyn Idwal.) 2.76
Glanrafon.) 2.79
Lyln Nantlle.) 2.80
Llyn Nantlle.) 2.82


Turkish Oilstones

1.) 2.60
2.) 2.63
3.) 2.63
4.) 2.64
5.) 2.73
6.) 2.62

The big outlier there is obviously No.5. This stone is a little different from the others, and is a superb razor finisher (most Turkish will not finish a razor). And for that, and a few other reasons, I don't think it's a Turkish actually now.

 

[cotedupy]

Charnley Forest

Larger - 2.72
Smaller - 2.70

Both of these stones are toward the finer and harder end of Charnleys. I've only ever had a couple of others tbh, but they were softer and coarser than these two. Probably doesn't say much that isn't obvious... they are quite similar to Idwals, though the latter is a little denser and harder than the Charnley stone. The reading for my relatively coarse Idwal above was higher than both of these.

 

[cotedupy]

Washita

1 (Pike Lily White) - 2.45
2 (30s/40s Norton Lily White) - 2.33
3 (30s/40s Norton No.1) - 2.19
4 - 2.35
5 - 2.36
6 - 2.21
7 - I've glued this to an India to make a combi, so can't measure.

Old Washita readings are always going to be a little screwy because of the porosity and how much oil is left in them. This will particularly apply to no.s 1, 4, and 5; which are very old, and despite being degreased off and on for probably several weeks in total, still have a significant amount of oil left in them. If fully degreased the readings for those would be lower I imagine.

4 & 5 are probably the two best Washitas I've ever had.

 

[bluesman 7]

Washita

I've glued this to an India to make a combi, so can't measure.

See

 

[cotedupy]

See

Ha... touche.

Though I still stand by my decision!

 

[rideon66]

SG of the red stone is 2.28
The Sharpening Stone Museum - https://www.badgerandblade.com/forum/threads/the-sharpening-stone-museum.631754/post-11983916

Fiddich is 2.74
Coticule really hard barber size 3.07
Cotiucle really hard pink 3.13
Coticule really hard lots of manganese lines 3.14
Coticule really hard old grey Bout Rustique 2.96

WOA 2.72

Charnley Forest stone Marples labeled boxed 2.68
Charnley Forest stone 2.69
Charnley Forest stone Marples lableled wide one 2.71

Now that odd Grey white thing I can't tell if it is a Charnley or a Turkey 2.619

TOS bout 2.51
TOS super dark almost Black 2.58

 

[Wid]

The white TOS I measured were close at 2.49.

 

[Steve56]

So what about coti combos?

I’ve seen some JNats to almost 2.7, you could feel the mass/weight in your hand. I sold that stone but have another in the wings. Most are around 2.3 - 2.4.

 

[Wid]

So what about coti combos?

I’ve seen some JNats to almost 2.7, you could feel the mass/weight in your hand. I sold that stone but have another in the wings. Most are around 2.3 - 2.4.

I’ll measure the LPB tomorrow. I’d just about bet it’s in the 3’s.

 

[rideon66]

So what about coti combos?

I’ve seen some JNats to almost 2.7, you could feel the mass/weight in your hand. I sold that stone but have another in the wings. Most are around 2.3 - 2.4.

Steve,

All the Coticules I mentioned are natural combos other than the Grey bout rustique since it is just a solid chunk of who knows what coti with no bbw side.

Are you asking about glued combos?

 

[Steve56]

More of a question of what you are measuring when you have two layers.