Glass Knives

A

Aleutblade

Joined
Sep 24, 2001
Messages
4
I've heard there are glass knives, they can be the sharpest edges, only a molocule thin, does anyone know anyhting about them or how theu can be made :confused:
 
Originally posted by Aleutblade
I've heard there are glass knives, they can be the sharpest edges, only a molocule thin, does anyone know anyhting about them or how theu can be made
Click to expand...
Interesting. The only time I've seen that, was in the SCI-FI book "Snow Crash", which is a classic in its way :).
The Aleutian guy called Raven, caried those knives piercing through the bolletproof vests. Eventually he ended up badly because of those glass knives, but that's irrelevant.
IMHO that's a fiction, I mean the "1 molecule think edge" part.

Other than that i am not sure.

P.S. Heard of sapphire blades btw. Either way those things are too brittle for general use.
 
Yeah, ive read that, but there are glass knives, i learned today they can be used in microscopy, my name has nothing to do with glass knives or raven
 
You are correct, but these knives are of no use other than to cut specimens to be looked at under a microscope. They can cut a thinner sample than any other type of knife, but the edges are extremely delicate. I am not sure about the one molecule thing, but they are incredibly sharp.
 
Aleutblade,
I don't much about glass knives except that I did see one for sale (w/box) about a year ago in a antique shop. It was from "The World's Fair" (I forget the year...sorry:o) The box claimed that it was a citrus knife. It was about 7" OAL with a 3" blade.

It would have been a nice addition to my collection.

Now I'm wishing I had bought it...

--The Raptor--
 
The edge on the molecular level thing is true.
But its not true of knive ground from glass.

An obsidian knife that has been knapped (chipped) like the indians used to to do it, will get an edge that thin.

My father is involved int he archeaological field and I have had the pleasure of meeting the two men (wish i could remember their names) who are considered, by people in the field, the premire flint knappers in the western US.

And they both told me the molecule thing, and its in several books we have here. SO I'd say its true.
 
Another name for obsidian is volcanic glass. I have seen pictures of arrow heads knapped from broken bottles. I work in a glass factory and see pieces of broken glass used daily for "knives".
Paul
 
I've got one around here somewhere.They are from the 1940"-'50's.Mine is pink glass and was used by My Great Aunt to cut cake for parties,etc.My example has a very ragged chipped edge.I've seen them at antique shops and flea markets,not commanding a very high price.Hope this helps.tom.
 
As a blade material, glass suffers a critical problem: it's not a solid. Glass is actually a liquid at room temperature -- a very, very thick liquid, but a liquid just the same. The glass that is sitting next to me is just as much a liquid as the beer it contains, it's just much, much thicker (a physicist would say that it's very viscous. Glass is a fluid that is so viscuos that we can actually use it for structural applications. This is why glass shatters instead of just breaking. When you strike the surface of a pool of water, it splashes in little droplets. Glass does the same thing. It splashes.

If you go to, for example, Europe where there are buildings with windows that have been standing for hundreds of years, what you'll find is that the panes are slightly, but measurably, thicker at the bottom than at the top. Over hundreds of years, the glass fluid has actually flowed down.

The problem with trying to make a knife blade out of glass is that like all fluids glass has surface tension. Water has a very high surface tension. If you put a drop of it on a table, you'll see how the edges of the drop become naturally rounded. That's what happens to an edge of glass too. It doesn't happen as quickly since glass is such a viscous fluid and it doesn't happen so dramatically since the surface tension of glass is lower, but it still happens.

You can see this easily. If you've ever broken a piece of glass, you know that the edges can be razor-sharp. But, if you've ever come across some glass that was broken even a few months ago, you know that the edges aren't so sharp anymore. Surface tension has rounded that edge over just as it does on a drop of water.

So, you could make a wonderfully sharp edge out of glass, but it wouldn't stay sharp. It would go dull sitting in a display case without ever being touched.

BTW, if you want to amaze your friends at cocktail parties, tell them that glass is, officially, in physicist-speak, an "amorphous superfluid."
 
I was taught the "glass is a liquid" and "glass windows deform" in School. I was suprised recently to learn that current science questions the validity of this belief after objective study. In the links below, one leaves open the possibility that some glasses might flow, but states that we know for sure that all glasses do not flow citing "stone age arrow heads made of obsidian, a natural glass ... found to be still razor sharp after tens of thousands of years". The other dismisses the flow of glass entirely.

http://math.ucr.edu/home/baez/physics/glass.html

http://www.ualberta.ca/~bderksen/florin.html
 
So my eyesight isn't getting worse, it's just that my glasses are dripping?
:D

FYI, the knives depicted above premiered at the 1939 New York World's Fair.
 
You must log in or register to reply here.
Back
Top