If you want to be super pedantic, use a loop of thin fishing line. It’s so thin it barely displaces any water, and it doesn’t tangle when wet, like, say, cotton thread.
Specific Gravity Confusion
- Thread starter cotedupy
- Start date
Fishing line is the way to go.
I’m an engineer, so I am willing to accept a certain tolerance. 
But I did use a very thin synthetic kite string rather than the thick cotton string that I use on my rotisseries chickens!
But I did use a very thin synthetic kite string rather than the thick cotton string that I use on my rotisseries chickens!One of my first finishing stones for razors was an old Smith calico hard ark. It has black spots in it that reacts to mineral oil like a black ark from norton or Dan's but the rest is slightly porous but very slightly. I remember this stone giving an amazing edge and I pulled it out today to use at work but never invoice it. I may do a wire up tomorrow. It's sg is 2.58 and I agree that it doesn't equate to fineness at all. The only reliable, sure fire way I've found to rate a stone is rub steel on it. I think that's part of my draw to it all.
Generally Dan's will tell you there's not a decernable difference between the two. I've found variations in both but they seem pretty evenly matched if you've got good examples of each. My old Norton translucent slip stone and black slip stone deliver the exact same edge as far as my face can tell. Im very glad i bought several black and trans arks and they've all turned out to be wonderful stones.
My favorite arks all come in around 2.55-2.59, regardless of their looks aside from one enigma. I think it's just had larger bound gains.
This may well be true. My Black Arks somehow seem easier to get a primo edge, but I can get a slightly different, crispy, edge with the Trans than the Black. All things being equal! Lube, lapping, flatness, surface finish, the same razors going back and forth from Trans to Black, in my house, frequently around 2:00 am, with an adult beverage and a killer playlist, over a period of years with no scientific evidence. YMMV Greatly. I feel I have to pay a lot more attention on the Trans. Does the Black Arks high SG impurity aid as a buffer, polisher, softener? I have no idea...
- Thread starter
- #28
Yep, what @Legion said is both the easiest and most accurate way to measure SG. FWIW though: when I measured the SG of your No.1 Washita in this way, the reading was only .01 or .02 different from what you'd measured it as. Which is basically nothing in the grand scheme of things!
- Thread starter
- #29
Here's a quick run down of how to do the water displacement test in case it's useful for anyone. You don't even actually need to weigh the stone dry, the whole thing takes about 5 seconds. Screenshots from a message I sent to someone on KKF a while back.
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- Thread starter
- #30
For translucents and blacks the difference is going be minimal in the extreme because they have very, very low porosity. Which is the reason it takes so long to get any oil out once it's there. Highly porous Arks/Washitas with loads of oil in them degrease far more quickly than ones with less oil. Easier in, easier out!
- Thread starter
- #31
It is yep. It'd be at the low end of Idwals - more common for a Charnley ime - but I do have an Idwal under 2.70 too.
Those two stones do look a bit like unusual Idwals, but they're not: the structure and feel is a bit different. I don't know anything quite like them tbh, they could be some kind of Cretan/Turkish, but they're definitely not the normal type.
In speaking with Halls back in the day, THEY judged Surgical black as the hardest/finest based exclusively on the fact that they went through more blades cutting them than anything else (including translucent). They also noted that it wasn't even close... I asked how they told "Black" hard ark from "Surgical Black" and they said the material was nothing alike... I forget the numbers they gave, but I think it was something like SB material burned through their saw blades 3-5x faster than hard ark and significantly faster than Translucent.
Yep - I had the same convo with them. Their black (not surgical) is Dunston stone, a type of Slate.
@Longhaultanker interviewed Dans about their Ultrafine black and Translucent stones and the takeaway was that it's marketing.
My personal take on this is that some SB Arks will be better for some people and some Trans Arks will be better for some other people.
But Specific Gravity though, seems that it's often misunderstood and misused.
I think the term Novaculite is misunderstood often also. That's another story....
And hardness - well, SG has nothing to do with hardness. Lead is SG 11.5 ... not hard though.
People get confused because in one context, a harder Ark with a higher SG is usually going to produce a finer edge.
Like, say, a Washita vs a Translucent.
So some people think oh, a SG of 2.5+ means finer.
No - not in a global sense for all stones all the time.
If I have a Trans Ark that is SG 2.7 and another that is SG 2.5... there is no guarantee that the SG 2.7 Ark is going to be 'finer', the higher SG only means it is more dense.
The actual crystalline makeup of the stone is most important.
Chalcedony, for example, is also crypto/micro crystalline silica, has SG of 2.5, but cannot compete with a Trans Ark as a razor hone.
Also, impurities will often raise the SG. That is why surgical blacks often have a slightly higher SG than translucent. Whatever it is in the stone that makes it black also raises the SG a little bit. Doesn't make it harder, and it is actually less "pure".
Impurities have a hand in it, black in Arks is indicative of Iron. Red in Arks is Hematite...
@Gamma I was unaware that it was iron that made it black, but it makes sense. I grew up on top of a giant iron or deposit, as big as the town I lived in almost. People think of iron or as red rock usually accompanied by lots of red clay but the really pure ore is almost black. I got this one around north Texas where a vein had gotten close to the surface and broken up. The thing feels like molten slash that's hardened. It's destined to become carbon steel and become a knife, but your statement set of a light bulb. Very interesting stuff.
Note - Iron impuriities turn different things different colors. Amethyst, for example, is purple because, in part, of iron in the quartz.
Were is this information coming from that it is iron turning the black ark black?
I'm sure that more work has been done with the archeologist community taking an interest in tracing novaculite to specific quarries but I don't think that information is on the net.
If we go way back to 1890 and the geological survey of Arkansas they think the black color is probably carbon.
Here on page 135...
If we go way back to 1890 and the geological survey of Arkansas they think the black color is probably carbon.
Here on page 135...
Annual Report of the Geological Survey of Arkansas
books.google.com
Annual Report of the Geological Survey of Arkansas
books.google.com
The coloring scheme, hematite red, iron black, etc - is a characteristic seen in Cherts - Novaculite is a form of chert. It's referenced in many places but one source I remember offhand is a paper on the Texas Novaculite deposits. Other places included papers or articles written by orgs in Hot Springs, a paper written by Ashley, forget the title but it had to do with outcroppings, and at least one piece by Arkansas Geological. I don't keep footnotes, they're too difficult to organize. Lab analysis done in Russia, checking psd, impurities, etc, also listed Iron for the black sample, it was not present in the translucent sample. I canont recall if carbon showed up in that analysis. In the grand scheme of things I don't suppose any of it matters, my reason for mentioning thiron and hematite was their fairly high SG. Manganese is another impurity associated with novaculite but I can't remember the details, also high SG.
Books from the 'old days' are great but sometimes the info is dated, has been superseded or just dismissed. I've read the Geological Surveys, Griswold's book too. Those writings were enlightening, just like Leske's cabinet was enlightening.
If we go back far enough we find Novaculite classed as Argillaceaus, and not Silaceous.
In the 1890s stones we refer to as Jnats were classed as Slate, today we class as shale.
Books from the 'old days' are great but sometimes the info is dated, has been superseded or just dismissed. I've read the Geological Surveys, Griswold's book too. Those writings were enlightening, just like Leske's cabinet was enlightening.
If we go back far enough we find Novaculite classed as Argillaceaus, and not Silaceous.
In the 1890s stones we refer to as Jnats were classed as Slate, today we class as shale.
