Thread: CBN strops.... a thought

Those kind of girls think hamburgers grow on trees :<0)

Originally Posted by Voidmonster

This is a commonly held misconception.

While glass might possibly flow given enough time, the rate of movement and prospective timescale means that for practical purposes glass flows slightly less than bismuth is radioactive.

Over the scale of tens of billions of years, there might possibly be movement within glass of about an atom's width.

I got to disagree with you. Even in our house which is just about 25 years old, there is discernible flow and ripple in the glass windows. I've also noticed that church and synagogue stained glass windows show the same rippling effect in windows that are older than a few decades. I've also experienced glass plates, like microscope slides, that if allowed to sit on top of each other for a relatively long (short?) time, like a year or so, they tend to fuse together. I remember rummaging through a bunch of University castoffs that included glass coverslips and microscope slides that were in original boxes from the 1930's. They were completely fused together something like a brick of glass. So, I've seen ample evidence that glass does flow, slowly be it, but still quickly enough to see distinct macro changes in a few decades.... micro changes like was commented on regarding plate glass (see prior post) probably can be seen within months or years of the manufacture of the glass plate.

Nope . The glass doesn't ripple. It was made that way.
How does glass change over time? | MIT School of Engineering

Originally Posted by DoctorSaul

No dog, but I could try to shave my cat. Now there is a challenge! I think my wife would throw me out if I started shaving my legs. I'm writing this through tears of laughter... you really made my day!

Well, you could try shaving badgers and add knot tying to you hobbies...If you survive the shave.

Originally Posted by onimaru55

Nope . The glass doesn't ripple. It was made that way.
How does glass change over time? | MIT School of Engineering

Hate to disagree with MIT School of Engineering, but I recall reading several papers that measured the flow of glass in old windows based on the thickness difference at the top vs the bottom of the pane. I'll try to find the references. Additionally, how else do you explain the phenomenon of glass plates sticking together when stored on top of each other for a long time (years, decades, etc.). I also recall some interesting electron microscope photos of two glass plates looking at the interface of the two, sideways, showing the melding of the two surfaces. I'll also try to dig up that reference, if I can find it. Finally, how do you explain the dishing effect on the windows in my 25year old home? The dishing effect certainly was not there when we moved into the house, but it certainly is quite pronounced now on most of the windows in the house. Even Anderson Windows acknowledged that the dishing effect is because of glass flow over time, when I inquired about our windows (not covered by their warranty, of course).

Originally Posted by DoctorSaul

Hate to disagree with MIT School of Engineering, but I recall reading several papers that measured the flow of glass in old windows based on the thickness difference at the top vs the bottom of the pane. I'll try to find the references. Additionally, how else do you explain the phenomenon of glass plates sticking together when stored on top of each other for a long time (years, decades, etc.). I also recall some interesting electron microscope photos of two glass plates looking at the interface of the two, sideways, showing the melding of the two surfaces. I'll also try to dig up that reference, if I can find it. Finally, how do you explain the dishing effect on the windows in my 25year old home? The dishing effect certainly was not there when we moved into the house, but it certainly is quite pronounced now on most of the windows in the house. Even Anderson Windows acknowledged that the dishing effect is because of glass flow over time, when I inquired about our windows (not covered by their warranty, of course).

You'll have to ask MIT. I just hone razors.

Slides are almost perfectly surfaced & will stick together immediately due to Van der Waals forces. Humidity would add to the adhesion. That's all I got.

You're seriously going to argue that the professor of Materials Science at MIT who runs the glass lab is wrong? Such hubris, man, my God. There are any number of reasons why things stick together after being in full and intimate contact for decades. Sorry, but this "glass is actually a very viscous liquid" stuff is just perpetuating misinformation, IMO. My house was built in 1950 and has very ripply windows, but I sure as heck don't think they're running down the frame. They were certainly made that way.

I've got a lead crystal double old fashioned glass that moves from my glass end table to my mouth. I challenge MIT to prove me wrong, plus, the contents seem to disappear over time.

Originally Posted by eKretz

You're seriously going to argue that the professor of Materials Science at MIT who runs the glass lab is wrong? Such hubris, man, my God. There are any number of reasons why things stick together after being in full and intimate contact for decades. Sorry, but this "glass is actually a very viscous liquid" stuff is just perpetuating misinformation, IMO. My house was built in 1950 and has very ripply windows, but I sure as heck don't think they're running down the frame. They were certainly made that way.

I should tell you that I spent a fourth of my career as a professor teaching physical chemistry on both the undergraduate and graduate level. There is more than ample evidence that glass is an amorphous, high viscosity, liquid.... and that it has a very low yield point, hence flows, albeit slowly, with time. The MIT guy is sorely mistaken or misquoted.

Originally Posted by onimaru55

You'll have to ask MIT. I just hone razors.

Slides are almost perfectly surfaced & will stick together immediately due to Van der Waals forces. Humidity would add to the adhesion. That's all I got.

You are right that VanderWaal forces are involved in keeping the surfaces in intimate contact. However, the melding of the surfaces into each other with time is an effect due to the flow of glass into each surface. With time, the demarcation between the two surfaces disappears. This has been demonstrated time and time again with old glass plates, especially old microscope slides or cover slips.

I don't know where the thought that glass does not flow originated, but the physical chemistry literature is chock full of evidence of the nature of glass as a highly viscous liquid with a relatively low yield point, hence, flows with time under the influence of gravity.