Why Is Glass Bowl Leaning?

[Trish66]

Over a period of three years one glass bowl has been leaning more and more. I purchased them at the same time. They were identical. I painted them at the same time with Gallery Glass Paints and varnished them at the same time with the same varnish. Both have been in an identical environment since. What is happening please? Media URL: https://youtu.be-rkSbHjuyxM
Description:

[Mamyalynne]

Let's try again

[RATTER15]

My guess is that they were always like this and you never noticed or they are not actually glass.

[RATTER15]

Could we see a pic looking directly on to the base?

[EDDIE51]

I agree with Ratter , glass does not 'bend' or deform,unless it is heated to red hot.

[mibn2cweus]

Not all 'glass' is silica based.

Some 'glass' has relatively low glass–liquid transition temperature.

https://en.wikipedia.org/wiki/Glass_transition

[mibn2cweus]

https://en.wikipedia.org/wiki/Glass

[EDDIE51]

^^ Yes but we are still talking about temperatures of over 230 Deg C .

[Chipchopper]

Similar perhaps but they can't be the "same"

[neuron]

Err, there are four instances of the word "same" in this thread Chipchopper. Please clarify what you mean.

[wildwood]

Could this bowl have been on top of an electric hot stove element?

[-Talbot-]

You're being very selective on where you have put the boat level. The blue one is clearly out of shape and if you spin the boat level round a bit it will not be level.

[mikey4444]

Actually, the idea that glass never bends or changes over time is really true.

If you look at old windows in an old house, you will notice that the glass is thicker at the bottom of the window, than it is at the top. That is why glass can still flow, albeit very slowly, over a long period of time.

Having said that, I doubt that your bowls are "true" glass, at least not pure glass. If these bowls are in a warm position, they may deform over time.

[neuron]

^^^^^^^^

http://www.open.edu/openlearn/science-maths-technology/science/physics-and-astronomy/physics/does-glass-flow-downwards

http://www.cmog.org/article/does-glass-flow

[mikey4444]

Thanks Nueron....It seems that I too, have been labouring under the wrong impression, since my 1960's Physics master first told me this !

[-Talbot-]

Thanks for the chuckle, mikey

[neuron]

Me too mikey! Likewise, my science teacher in the mid sixties was always on about solid, liquid and gas being the only states of matter yet was happy to tell us about glass flowing in these way. I was not happy with the explanation then.

Still, it was the same bloke that provided us with a map of the human tongue showing where the individual taste buds for sweet, sour, bitter and salt were located. The whole theory has been disproven in recent years. I often think of the day we undertook a class experiment with sugar, lemon and salt to prove that these areas existed for ourselves! What a waste of time.

[beso]

Your teacher was wrong about three states of matter too. Without even considering exotic states that exist under extreme gravitational conditions, there are at least four.

Plasma is a common state of matter that is as different as the familiar three are from each other.

[neuron]

Thanks Beso. I made the point to illustrate how knowledge is constantly progressing and how some of us were effectively misled in our teenage years regarding science topics. No one was to blame as after all, our teachers could only impart the knowledge they had themselves.

[theprof]

I was browsing a copy of DG Mckean's Introduction To Biology textbook that I was provided with in my early teens the other night and came across the "tongue-map". The whole idea is hilarious nowadays and we still discuss it in the uni Senior Common Room's now and again.

I also remember being taught the metabolic pathways involved in photosynthesis during my "A" level Botany. At that time, only one method of photosynthesis existed and our textbooks were supplemented by the magnificent Nicholson's Metabolic Pathways Chart published by Koch-Light Laboratories and pinned to the school botany lab wall. Nowadays, those early charts are out of date and contain quite a few errors that have been corrected in subsequent years. The same applies to the animal biological pathways that were shown.

[EDDIE51]

I remember the teacher in my school physics class asking us 'Is glass a solid or a liquid' every one apart from me said 'Solid' . But I knew it was a supercooled liquid with a viscosity of several million poise and told him so. He was impressed that I knew, I was only 12 . I loved Physics and normally got 100% in exams.
The viscosity is why ancient glass is thicker at the bottom as mikey says, it has 'flowed' over the centuries.