Anyone good at making flint/obsidian/stone/glass knives?

stitchawl said:
A couple of points (no pun intended.) First, neither flint nor obsidian get any sharper than a very well sharpened knife.

Stitchawl
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Physically they do have to potential to get many times sharper than steel, we're talking down to a molecule or two thick at the edge. But, just as you said they don't survive first contact very well.
 
spareparts said:
Physically they do have to potential to get many times sharper than steel, we're talking down to a molecule or two thick at the edge. But, just as you said they don't survive first contact very well.
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Can we please see the ones you've made that have edges a molecule or two thick.
Or perhaps the ones anyone's made that have edges a molecule or two thick. Cuz in all the years I was knapping, going to knap-ins and shows, I certainly never ran into any. Flint gets sharp. Obsidian gets even sharper as does glass. It's in the nature of the fracture. A pressure flake is a very sharp edge, but you can certainly sharpen a good steel just as well. Which might explain why surgeons used steel instead of broken glass.


Stitchawl
 
Obsessed with Edges said:
Uh oh... NOW you've done it! :eek:

Somewhere, in a dingy cubicle deep in the bowels of the TSA, an employee is sitting at his computer, taking notes and preparing a memo, to update the 'Prohibited Items' list on airline flights. "No SHARP ROCKS allowed!!", is what we'll see posted at the security checkpoints next time... :D
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Once a TSA guy did question my flint striker as it was "D"- shaped like Brass knucks... but he let it though. I've since made a new striker in a "J"- shape that doesn't seem to arouse any curiosity.

Just kidding, Stitch. Good to hear from you again. ;)
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I've been here all along, lurking in the background. I just got tired of responding to posts where the OP could have spent five minutes with the search function rather than have people repeat themselves over and over.

How many times can we answer "Which should I use, peanut butter or margarine, on my new suede strop?" Better to let Richard convert them all to using paper wheels... (Am I getting cynical in my old age?)

Stitchawl
 
stitchawl said:
How many times can we answer "Which should I use, peanut butter or margarine, on my new suede strop?" Better to let Richard convert them all to using paper wheels... (Am I getting cynical in my old age?)

Stitchawl
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How can you blame your old age right after taking a childish cheap shot?
 
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stitchawl said:
Can we please see the ones you've made that have edges a molecule or two thick.
Or perhaps the ones anyone's made that have edges a molecule or two thick. Cuz in all the years I was knapping, going to knap-ins and shows, I certainly never ran into any. Flint gets sharp. Obsidian gets even sharper as does glass. It's in the nature of the fracture. A pressure flake is a very sharp edge, but you can certainly sharpen a good steel just as well. Which might explain why surgeons used steel instead of broken glass.


Stitchawl
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Never said I was a knapper.

Ok, I over estimated, lets just say that obsidian at 3nm gets 166x's minimum sharper than a razor blade. That still makes it sharper than any steel knife that anyone here owns. I do have to say thanks for calling me out, I learned quite a bit about obsidian and blade edges fooling around on google.

Blades made out of obsidian rock are ultra-thin, with tips that can be as narrow as 3 nanometers
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http://www.universetoday.com/60879/obsidian-rock/

A nanometre (American spelling: nanometer; symbol nm) is a unit of length in the metric system, equal to one billionth of a metre. The name combines the SI prefix nano- (from the Ancient Greek νάνος, nanos, "dwarf") with the parent unit name metre (from Greek μέτρον, metrοn, "unit of measurement").
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http://en.wikipedia.org/wiki/Nanometre

2. Modeling of the Cutting Interaction
2.1 Simplified Model of Pressing and Slicing Cuts on Hard-Crispy Materials
The illustration of potato cutting is shown in Fig. 1. The modeling and experiments will focus on using the
blade shown in Fig. 1(a) to realize the robot controlled cuts shown in Fig. 1(b). The micro-structure photo of the
edge of a blade is shown in Fig. 2(a) with the measured width of the blade cutting edge. For that particular razor
blade, the edge of this blade is 850nm with flat surface. The range of the edge width of a brand new blade is
around 500nm to 1250nm with the shape shown in Fig. 2(b).
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www.hindawi.com/journals/mse/aip/469262.pdf
 
I should have realized that if it says so somewhere on the Internet, it must be accurate. The Internet only has factual information. Please excuse me for ever doubting you.


Stitchawl
 
stitchawl said:
I should have realized that if it says so somewhere on the Internet, it must be accurate. The Internet only has factual information. Please excuse me for ever doubting you.


Stitchawl
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My humblest apologies for not taking your word as truth on the internet. I retract my previous statements and publicly admit that stitchawl's opinion should be taken for truth just because he says so...and citing sources is tedious anyway.
 
spareparts said:
My humblest apologies for not taking your word as truth on the internet. I retract my previous statements and publicly admit that stitchawl's opinion should be taken for truth just because he says so...and citing sources is tedious anyway.
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I never asked you to believe me. I stated what "I" knew to be true. I only asked to be shown these wonder edges. So far, all I've gotten is opinion. Just like mine, with the one difference being that I was involved in knapping for many years and based my opinion on what actually existed in the knapping world around me.

As for citing sources, I can site sources that 'prove' the Holocaust never happened, despite the fact that many of us have relatives who were affected by it. "Proof," just because it's cited on the Internet, does not mean it actually is. However, please feel free to believe what ever you wish to. Please allow me the same freedom.


Stitchawl
 
You can read one of the original research papers in which they investigated obsidian knives for eye-surgery. It was published in 1982 in the Western Journal of Medicine, and is indexed on Medline. If you have proven that the paper's results are invalid, then that result, itself, can be published as a paper.

The paper is free to download, and you can grab it here:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1273673/?tool=pubmed

This paper is referenced in both the link that Bob W mentioned, and Wikipedia's entry on obsidian.
http://en.wikipedia.org/wiki/Obsidian#Current_use

I would like to say that different people have different experiences.

That doesn't mean one is right and one is wrong. For example, there could be differences in skill, materials, and hundreds of other effects. For example: obsidian is mostly silica, but it has other stuff in it. But the other stuff probably matters, just like a fraction of a percent of carbon changes soft iron into hard steel. So there a many possibilities. I'd rather we weren't snippy about it. I think it's better to simply say,"Hmm... In my experience that never happens, so and I have a hard time believing it," rather than various ad hominem attacks.

Different experiences are fine by me, and I'm curious about each of them.

In my own opinion, I tend to think both the scientific paper and stichawl are both valid. And what it _could mean_, is that obsidian can get insanely sharp, but in practice, it maybe be extremely hard to do. If so, then that itself is disappointing, but very interesting.

Sincerely,
--Lagrangian

P.S. Like RazorSharp-Travis, I might try breaking some bottles, even if they aren't obsidian. :D
 
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Bob W said:
Not broken glass, obsidian. And it is sometimes used for surgical scalpels because it's much sharper than steel blades.
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May I ask how you are differentiating between 'glass' and 'obsidian' other than being formed by different creators?

Looking at some of the links provided, I see is a few people 'saying' obsidian makes a sharper edge. Some of these edge makers state that as they are hand made, they are few in number. Raises the question that if they are so superior, why are only a few being made? It can't be because only a couple of people can knapp... Remember the old 'Build a better mousetrap' line?

If they are so good, why are then NOT permitted to be used? And if for a moment we simply accept that they cause less scaring (which seems to be debatable,) why are they NOT in general use for cosmetic surgery? If it were truly this superior cutting instrument for soft tissue the demand would be there. Price certainly isn't a consideration in medicine today, not when one pill can cost $150.00

There is just waaaay too much anecdote and not enough fact. I know that knapped obsidian is sharp. I've cut myself enough times to be convinced. But I've cut myself just as many times with a steel blade... Paper cuts are painless too. Is a sheet of paper as sharp as a razor?

Stitchawl
 
If any of you who have a real job, then spending $78.00 to get a surgically-sharp commercial obsidian blade might be very interesting. It is a lot of money to satisfy curiosity, but if you've an uber-knife enthusiast, many of us would be fabulously curious if you got one and tested it (carefully, as it's probably easy to chip and dull after light use).

Or if you are willing to paypal me $78 (I'm curious enough to pay for shipping), then I'll test it for you, and make a video. Before running the tests, I would need us to have a discussion about what tests to do, exactly how to do them, and how to run a control.

Otherwise, if there are say, 10 of us, each willing to donate $8, that is another way we could get the funds. I would suggest that someone who seems very knowledgeable about sharpening/sharpness run the test, however that person should be relatively unbiased.

Link to purchase, as posted by Bob W (thanks Bob W! :thumbup:):
http://www.finescience.com/Special-Pages/Products.aspx?ProductId=296&CategoryId=56

Who is interested? :) I'm down for contributing $10, and if I am the one to test it, I'd also pay the shipping costs.

Sincerely,
--Lagrangian

Bob W said:
Not broken glass, obsidian. And it is sometimes used for surgical scalpels because it's much sharper than steel blades.

You can buy them here: http://www.finescience.com/Special-Pages/Products.aspx?ProductId=296&CategoryId=56

Interesting discussion here, including why it's not used more often:
http://averyremoteperiodindeed.blogspot.com/2011/03/obsidian-blades-as-surgical-tools.html
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If we _actually_ do this, then I'd also propose that the tester get some knives sharpened by others to a level they believe is "sharper than obsidian" to test against. Those knives could either be sent by the tester to the sharpener and back, or they could be loaned by the sharpener to the tester.

Also, knappers should be allowed to submit obsidian/glass knives they think are very sharp to compare to (against the metal knives). These will have to be packaged and shipped very carefully.

Hey we're amateurs, but what do you say guys? Let's try to do some science! :)
It won't be perfect, but it will be fun, and hopefully informative.
 
As we know, there are _many_ types of steels so people form charts to compare compositions of different steels.
http://zknives.com/knives/steels/steelchart.php

Similarly, there are _many_ types of glass, each with different properties. Just to give you an idea, here is what I found out about some common types of glass:

(1) soda-lime glass: 75% silica, Na2O, CaO
(2) fused quartsz: almost 100% silica depending on purity
(3) borosilicate glass ("Pyrex"): 70% silica, 10% boron oxide, 8% sodium oxide, 8% potassium oxide, 1% calcium oxide
(4) lead glass/lead crystal: Mostly silica, but contains _lead-oxide_ 18%–40% by weight, plus other ingrediants. Lead glass has so much lead in it, you should NOT store wine in it for long periods of time (ie: more than a day), or some of the lead will leach into the wine. Lead crystal is a very soft glass (easy to cut and polish), with a very high index of fraction that makes it look very sparklely. This is why it is prefered by glass engravers.
(5) obsidian: varies depending on geology of the sample, but typically 70% silica plus other minerals (othoclase, plagioclase, hornblende, pyroxene,....) Honestly, I have no idea what these other minerals are.

Sources:
http://en.wikipedia.org/wiki/Glass
http://en.wikipedia.org/wiki/Borosilicate_glass
http://en.wikipedia.org/wiki/Obsidian
http://en.wikipedia.org/wiki/Felsic

Sincerely,
--Lagrangian
 
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Lagrangian said:
If any of you who have a real job, then spending $78.00 to get a surgically-sharp commercial obsidian blade might be very interesting. It is a lot of money to satisfy curiosity, but if you've an uber-knife enthusiast, many of us would be fabulously curious if you got one and tested it (carefully, as it's probably easy to chip and dull after light use).
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Why not make your own? It's very easy to 'pressure flake,' especially if you are not trying to maintain a specific resulting shape...
Pressure flaking isn't difficult. The hard part is controlling the remaining shape of the piece you are trying to make after flaking off spieces, i.e. the arrow head or spear point. It might take you 10 minutes to figure out how to produce razor-thin sharp flakes. The skill of knapping is getting what's left AFTER the knapping. These small flakes themselves are 'self sharpening...' Ask anyone who knapps.

Every knapper has made ultra-sharp flakes while trying to make their points. These little shards are the discards but certainly sharp enough to shave with. The only reason they are discards is because of their size. I see that the size of these 'scalpels' being offered are either 6mm or 12mm. You can find them by the thousands at every knapp-in.

And I guess the real test of their sharpness can be; will it push cut toilet paper?

Stitchawl
 
stitchawl said:
Why not make your own? It's very easy to 'pressure flake,' especially if you are not trying to maintain a specific resulting shape...
Pressure flaking isn't difficult. The hard part is controlling the remaining shape of the piece you are trying to make after flaking off spieces, i.e. the arrow head or spear point. It might take you 10 minutes to figure out how to produce razor-thin sharp flakes.
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I'll consider it! Thanks :D

Sincerely,
--Lagrangian
 
stitchawl said:
Why not make your own? It's very easy to 'pressure flake,' especially if you are not trying to maintain a specific resulting shape...
Click to expand...

Lagrangian said:
I'll consider it! Thanks :D
Sincerely,
--Lagrangian
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There are dozens of very good YouTube videos to show you the different techniques. Most new knappers ONLY make flakes...It's what is removed when trying to make a specific shape.
It takes a LOT of time, skill, and practice to get a good remaining shape.
It takes no effort at all to make a pile of flakes... Most of us spent weeks just making piles of flakes before we actually had a good point remaining. That's why it's suggested to start with broken bottle bottoms. They are free.

Stitchawl
 
Here, lets try to resurrect some civility in this thread with some "Oooh, Ahhh" worthy photos of a couple of truly outstanding knapped blades I own, done by a master - Scott VanArsdale of Wasicun Knives. I can only aspire to this level of craftmanship, but I do have a large chunk of Lassen obsidian waiting for me to work with.

Gold Fiber Optic glass with a Lignum Vitae grip
lvitae.jpg


Rainbow Obsidian with a Vermont Marble grip
166.jpg


Truly outstanding pieces, both of them.

Let's chip some stone, not hurl it, m'kay?:D
 
Lagrangian said:
If any of you who have a real job, then spending $78.00 to get a surgically-sharp commercial obsidian blade...
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The price alone is probably enough to explain why obsidian blades aren't used more in surgical procedures. Obsidian, $78. Disposable steel blades, 78 cents.
 
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