Polishing sanding scratches out of glass.

[Michael Kellough]

Which abrasive scratched the glass?

Not sure where I got the idea that aluminum oxide wouldn’t scratch glass. Is that true or false?

 

[Cheese]

Not sure where I got the idea that aluminum oxide wouldn’t scratch glass. Is that true or false?

Here ya go Michael...

[attachimg=1]

 

[AlexThePalex]

Which abrasive scratched the glass?

Not sure where I got the idea that aluminum oxide wouldn’t scratch glass. Is that true or false?

It was Festool Granat on the DTS, 120 grit, but only used sparingly. Most damage was done by hand sandpaper, I don't know which.

Every sandpaper can scratch glass.

 

[AlexThePalex]

Well, I'm thinking a RAP 150-21 FE spinning at 900-2100 RPM is in your future.  [big grin] 

Ha, I think I do want one,  [smile] But too much money for the limited use I'd get out of it. I think the RAS will do for this little problem right now.

 

[FestitaMakool]

Well, I'm thinking a RAP 150-21 FE spinning at 900-2100 RPM is in your future.  [big grin] 

Ha, I think I do want one,  [smile] But too much money for the limited use I'd get out of it. I think the RAS will do for this little problem right now.

Solution: Cheese might enjoy the Dutch dikes and canals off season, to see the non-postcard stereotypes scenic views..
Bring him and his arsenal over  [wink] [big grin]

 

[bertv]

Which abrasive scratched the glass?

Not sure where I got the idea that aluminum oxide wouldn’t scratch glass. Is that true or false?

It was Festool Granat on the DTS, 120 grit, but only used sparingly. Most damage was done by hand sandpaper, I don't know which.

Every sandpaper can scratch glass.

I remember reading somewhere that glass will always stay fluid. So maybe the scratches will disappear by themselves thru gravity in a few centuries…

 

[Crazyraceguy]

I remember reading somewhere that glass will always stay fluid. So maybe the scratches will disappear by themselves thru gravity in a few centuries…

I have heard that somewhere too. "They say" that if you take out the window panes from a really old building, the glass is thicker at the bottom, from sagging over time. I don't think any of us have the time to see if that works out though....lol

 

[AlexThePalex]

Solution: Cheese might enjoy the Dutch dikes and canals off season, to see the non-postcard stereotypes scenic views..
Bring him and his arsenal over  [wink] [big grin]

Hm, that would be cool if I could borrow Cheese's RAP.

I remember reading somewhere that glass will always stay fluid. So maybe the scratches will disappear by themselves thru gravity in a few centuries…

Yeah, well, I ain't got time for that.  [tongue]

I have heard that somewhere too. "They say" that if you take out the window panes from a really old building, the glass is thicker at the bottom, from sagging over time. I don't think any of us have the time to see if that works out though....lol

I've read that too. So when I had to replace a broken window of 80 x 40 cm they said was at least 120 years old, I brought my calipers to see if I could detect anything. I didn't notice any difference.

 

[Crazyraceguy]

That was the point of the quote marks on the "they say". I'm not so sure about random, unproven claims like that either. It's purely anecdotal because they can't possibly prove that it wasn't that way to start with.

 

[Cheese]

That was the point of the quote marks on the "they say". I'm not so sure about random, unproven claims like that either. It's purely anecdotal because they can't possibly prove that it wasn't that way to start with.

An interesting article from Scientific American.

Bottom line..."A mathematical model shows it would take longer than the universe has existed for room temperature cathedral glass to rearrange itself to appear melted."
https://www.scientificamerican.com/article/fact-fiction-glass-liquid/

 

[AstroKeith]

Glass flowing is a myth. True its close to being a liquid, but against that it has tremendous chemical bonds between atoms and molecules that liquids dont have.

Its been calculated that typical old glass would flow by 1nm over a billion years. Interestingly, the lead holding the glass in old windows would flow about a billion times faster!

Glass has only been made flat for the last 70 years (Pilkington's float method), before that the thickness varied enormously over even a small pane in manufacture

 

[squall_line]

I haven't read that specific article, but I've read and researched enough to adhere to the conclusion that any instances of old glass that is thicker at the bottom than at the top is that way because a) flat glass was spun to flatten and then cut, resulting in uneven thickness, and b) all things equal, it's easier to install glass with the thicker part down because the thicker part is heavier and has a wider, more stable base.

 

[Crazyraceguy]

Glass has only been made flat for the last 70 years (Pilkington's float method), before that the thickness varied enormously over even a small pane in manufacture

Yes, that is why large "picture windows" became praised/valued when they were first available. Before that large window spaces were comprised of many smaller panes with mullions and muntins separating them like tiles.
Those small panes were made by blowing glass into cylinders. Then cooling and cutting the ends off, splitting the tube into two half circles, reheated to lay flat. It was a lot of work and that's how the bubbles and waves got in there too.

 

[FestitaMakool]

Love the bubbles and waves.. [wink]

As a owner of an old house, my outhouse has pretty wavy glass. An acquaintance of mine was by one time, looked at the old windows and said: “Will be good once you get rid of those shitty old windows”
I didn’t say anything, just looked at him and thought: “You have no clue, have you”.. then we had coffee  [big grin] [big grin]

 

[Packard]

Not really on topic, but interesting anyhow.  I drove into a small down in upstate New York about 50 years ago.  The local restaurant had a front window comprised of many small panes of glass. 

Each (approximately 12 x 12”) pane bellied out so that it was convex on the outside and concave on the inside.  The net result was that the patrons in the restaurant had unimpeded vision out the glass. 

But people looking in from the outside saw greatly reduced images of what was going on inside.  Each pane appeared to have the same optical image of a greatly reduced restaurant interior.  The images were so small that no one inside was recognizable. 

It afforded a lot of privacy without seeming to.  The people inside saw undistorted images and on the outside, microscopic images. 

It always impressed me.  Of course that was before double pane and e-glass.  So this would probably never happened in 2021.

I apologize for the digression.

 

[Cheese]

I drove into a small down in upstate New York about 50 years ago.  The local restaurant had a front window comprised of many small panes of glass. 

Each (approximately 12” x 12) pane bellied out so that it was convex on the outside and concave on the inside.  The net result was that the patrons in the restaurant had unimpeded vision out the glass. 

But people looking in from the outside saw greatly reduced images of what was going on inside.  Each pane appeared to have the same optical image of a greatly reduced restaurant interior.  The images were so small that no one inside was recognizable. 

It afforded a lot of privacy without seeming to.  The people inside saw undistorted images and on the outside, microscopic images. 

It always impressed me.  Of course that was before double pane and e-glass.  So this would probably never happened in 2021.

I apologize for the digression.

No apology necessary...I've certainly side-tracked my share of threads.  [smile]

I think that's a great observation...the old precursor to privacy glass without tinting the windows or applying light reduction film to them. An early attempt at letting the sun shine in but keeping the prying eyeballs out.

 

[JeromeM]

I remember reading somewhere that glass will always stay fluid. So maybe the scratches will disappear by themselves thru gravity in a few centuries…

I have heard that somewhere too. "They say" that if you take out the window panes from a really old building, the glass is thicker at the bottom, from sagging over time. I don't think any of us have the time to see if that works out though....lol

Both the glass stays fluid and the old buildings have thicker glass at the bottom because it sags over time are complete myth.

NO glass is not fluid and NO it doesn’t sag over time.

The reason for glass being thicker in old windows (pre 1834) is that it was made by blowing glass, piercing the bubble then spinning it into a disk (the crown process), this process produced a flat circle of glass, though the thickness was not uniform, that was cut for windows, the cheapest, and incidentally strongest, was the centre or bullseye that was bought by pubs for their windows. The glass cut for regular windows varied in thickness and it was probably felt that the thicker part should be fitted at the bottom.
The other method was broadsheet glass, invented in Britain in the early 17th century, a lengthy balloon of glass that was blown, and then both ends of the glass were removed, leaving a cylinder to be split and flattened. Again having 2 bullseye pieces and the flattened sheet was not uniform thickness.

 

[AlexThePalex]

I apologize for the digression.

Fine with me. I think I've learned here what I needed to know, I don't mind if the rest of this discussion is about anything glass related you can think of.

 

[Crazyraceguy]

I apologize for the digression.

Fine with me. I think I've learned here what I needed to know, I don't mind if the rest of this discussion is about anything glass related you can think of.

I agree completely. Once the original topic is effectively resolved, why not learn something? It adds to the enrichment of everyone, especially since this particular group spans many countries, while having a commonality in the tools, yet we may all use/see them differently too. "You don't know what you don't know" even in your own country/culture. It's even better across them. I have learned a lot from this forum, especially the European members.
Derailed again....