Author Topic: Polishing sanding scratches out of glass.  (Read 3572 times)

0 Members and 1 Guest are viewing this topic.

Offline AstroKeith

  • Posts: 215
Re: Polishing sanding scratches out of glass.
« Reply #30 on: November 12, 2021, 12:37 PM »
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
Retired engineer/scientist

Festool USA does not pre-approve the contents of this website nor endorse the application or use of any Festool product in any way other than in the manner described in the Festool Instruction Manual. To reduce the risk of serious injury and/or damage to your Festool product, always read, understand and follow all warnings and instructions in your Festool product's Instruction Manual. Although Festool strives for accuracy in the website material, the website may contain inaccuracies. Festool makes no representations about the accuracy, reliability, completeness or timeliness of the material on this website or about the results to be obtained from using the website. Festool and its affiliates cannot be responsible for improper postings or your reliance on the website's material. Your use of any material contained on this website is entirely at your own risk. The content contained on this site is provided for informational purposes only and does not constitute professional advice.


Offline squall_line

  • Posts: 1032
Re: Polishing sanding scratches out of glass.
« Reply #31 on: November 12, 2021, 12:39 PM »
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.

Offline Crazyraceguy

  • Posts: 831
Re: Polishing sanding scratches out of glass.
« Reply #32 on: November 12, 2021, 06:02 PM »

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.
CSX
DF500 + assortment set
PS420 + Base kit
OF1010
OF1400
MFK700 (2)
TS55, FS1080, FS1400 holey, FS1900, FS3000
CT26E + Workshop cleaning set
RO90
RO125
ETS EC 125
RAS115
ETS 125 (2)
TS75
Shaper Origin/Workstation

Offline FestitaMakool

  • Posts: 1063
Re: Polishing sanding scratches out of glass.
« Reply #33 on: November 12, 2021, 06:22 PM »
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 bad 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]
“The Stig” Yes, it is true, at least some part of it..
“If you have an old Land Rover and a fit wife, you’re most likely always busy”

Offline Packard

  • Posts: 854
Re: Polishing sanding scratches out of glass.
« Reply #34 on: November 12, 2021, 06:27 PM »
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.

Online Cheese

  • Posts: 9108
Re: Polishing sanding scratches out of glass.
« Reply #35 on: November 12, 2021, 09:33 PM »
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.

Offline Sometimewoodworker

  • Posts: 783
    • Jerome's  Other work
Re: Polishing sanding scratches out of glass.
« Reply #36 on: November 12, 2021, 10:57 PM »

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.
Jerome
TS55, OF1400, Elu MOF96, Rotex150, DTS400, ETS150/3 Domino, MFK700, CXS, HL 850, Trend T11, Makita LS1212, Original Mini CV06 Cyclone, Workshop supplies drum sander, & WoodRat. Don't have don't want list: MFT
http://www.flickr.com/photos/nui-jerome/

Offline Alex

  • Posts: 7740
Re: Polishing sanding scratches out of glass.
« Reply #37 on: November 13, 2021, 12:11 AM »
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.

Offline Crazyraceguy

  • Posts: 831
Re: Polishing sanding scratches out of glass.
« Reply #38 on: November 13, 2021, 08:50 AM »
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....  ;)
CSX
DF500 + assortment set
PS420 + Base kit
OF1010
OF1400
MFK700 (2)
TS55, FS1080, FS1400 holey, FS1900, FS3000
CT26E + Workshop cleaning set
RO90
RO125
ETS EC 125
RAS115
ETS 125 (2)
TS75
Shaper Origin/Workstation