Polishing sanding scratches out of glass.

[AlexThePalex]

Anybody know how to polish sanding scratches out of glass?

A painter working for us made a lot of damage to about 10 windows, sanding by hand and with the DTS400. Instead of only sanding the wood around it he also made wide scratches on the first 5 centimeters of the glass and sometimes even in the middle of the window.

The scratches are not deep, but very noticeable. We contacted a specialised company and they didn't want to take the job, saying there is no guarantee they can make it right. The alternative would be to replace all the 10 windows, which would cost 5000 euro in material alone, without installation.

 

[AstroKeith]

Ouch!

I work with glass to make telescope mirrors. You would have to get a range of grinding and polishing compounds and using a padded buffer work through the compounds. A very long job. Plus clean up and change the pad every time you go to a finer compound - the coarse compound must be completely removed before progressing to a finer.

Normal window glass isnt as hard as some glasses, but it is still very hard!

Can you claim against the painter?

 

[usernumber1]

search google and youtube for Cerium Oxide

can be messy and lots of work or easy with a specialized setup

 

[Bob D.]

I have no idea if this would work but as I was reading this thread I
thought "I wonder if the technique used to fill scratches and cracks
in auto windshield glass would work?"

I don't know what the process is called but maybe a phone call to
a auto glass replacement company could shed some light on the
feasibility of this.

Not what I was thinking of but is this possible for your situation?

 

[Vondawg]

If the scratches are anything like what we went thru years ago (same circumstances) they will probably not polish out …..we ended up ordering and installing/replacing the glass….wasn’t fun

 

[Packard]

My first inclination is to do a google search for "optometry equipment and supplies".  You will probably find what you need there (though most glasses nowadays are made of plastic).

My second thought was "glass polishing", and that was a good search: https://www.google.com/search?client=firefox-b-1-d&q=glass+polishing+kit

 

[Chainring]

search google and youtube for Cerium Oxide

can be messy and lots of work or easy with a specialized setup

Exactly what I was going to recommend. I have a bottle from CarPro and it's designed to be used with some polishing pads that have almost no cushion.
https://www.autogeek.net/carpro-ceriglass-polish.html
https://www.autogeek.net/carpro-rayon-glass-polishing-pad.html

 

[Packard]

Are they double-glazed or single-glazed?  Are they large or small?

Small pieces of single-glazed glass are cheap and it probably would be easier to replace the pieces.

Double glazed and larger pieces can get expensive though.

I was a picture framer and I cut lots of glass.  It is not difficult, but be careful because glass cuts are nasty. 

It is probably easier to remove the old glass and carry it into a glass shop and say, "match these".  They should be able to do the work (single glaze) while you wait. 

 

[FestitaMakool]

Alex, Ouch!

If the scratches aren’t too deep, I think it may be polished.
As Bob D. suggests an auto glass car shop may be a good start. Although any entrepreneur which specialises in glas facades may also be a good start. I’ve seen, but know little, that there have been specialists done surface repairs to windows, usually on the inside where there’s no coating - replacing large sheets of high tech glass panels costing 5 grand and upwards are worth a try, even for large entrepreneurs..

 

[Crazyraceguy]

Wow, that sucks.
One window, sure deal with it. But some idiot doing the same thing to 10?!
If one company already turned the job down, it's not likely that anyone else will take it either.
Any time and effort that you put into shopping the job around (or trying to fix it yourself) only to have to get it replaced anyway, is wasted.

I have no idea how the law works there, but in the US, the company that did this would be liable for the cost of repair or replacement.

 

[squall_line]

I couldn't tell from the original posting if the "painter doing work for us" was a sub or an employee.  If it was a (possibly now former) employee, the liability/recoverability may not be there, unfortunately.

I'm interested in the results of this because it appears that someone did something similar on some of the windows of my house many years before I bought it; swirl marks in the corners that look like they're from either paint prep gone haywire or a drill-based glazing putty removal gone askew.

 

[Cheese]

Hey Alex you could try 3M glass polishing compound. I've never used it but Mother Mining products are generally pretty darn good.  [smile]
https://www.3m.com/3M/en_US/p/d/b40065564/

[attachimg=1]

 

[Packard]

That 3M stuff seems like the right stuff.  Here's 3M's data on that.
https://www.3m.com/3M/en_US/p/d/b40065564/

There are a couple of videos out there.  Not particularly well-edited, but a good demonstration.  Glass is a very hard surface.  It would not surprise me if this turns out to be a long and tedious process.

 

[AlexThePalex]

Thanks for the replies guys. That 3M stuff looks promising. And looks like Cerium Oxide is the way to go.

After googling I found Mirka has a kit which includes a lot of Abranet papers in different grits, made especially for glass, and polishing compound for the final finish. I think I'm going to order that and a bottle of 3M polishing compound.

I was first thinking of using the Rotex as that's my polisher, but after seeing that video above I'm starting to think I need the RAS instead?  There is even an old glass polisher made by an independent company called Scratch-Away which used the RAS as their basis.

And the painter, he's an employee, and still is. Mistakes happen.

 

[Cheese]

I was first thinking of using the Rotex as that's my polisher, but after seeing that video above I'm starting to think I need the RAS instead?  There is even an old glass polisher made by an independent company called Scratch-Away which used the RAS as their basis.

That makes sense Alex as I thought I read that 3M is looking at something over 1200 rpm and I think the Rotexes are all in the 600 rpm range.

 

[FestitaMakool]

I won’t be absolute here, but dual action (DA) as Rotex, polisher I’d maybe be careful with.
You may need to touch lightly, tilting the polisher ever so slightly - and with a DA polisher on presumably thin glass.. ai.. and the vibrations these provide..
Be careful and we might learn something her Alex - crossing fingers for success and learning something new! [wink]

 

[Packard]

I’d be really interested in how long it takes to polish out deep scratches.  We should have a betting pool.  I my bet is on 2 hours for fairly deep scratches.

It ain’t gonna be easy. 

I used to polish the headlight covers on my 1967 Alfa Duetto Spyder.  I didn’t have buffing compound.  I used Colgate tooth paste.  It took a while.  I also polished the rear clear vinyl window with Colgate.  My car had the best breath in the neighborhood.

 

[Crazyraceguy]

My fault. I assumed because of "a painter working for us" took me straight to sub-contractor.
Shouldn't have assumed.

 

[AlexThePalex]

I’d be really interested in how long it takes to polish out deep scratches. 

ROFL, I am so totally not interested in finding out.  [tongue] [big grin]

I don't think the scratches are deep, how deep can you get with sandpaper of grit 120?

I won’t be absolute here, but dual action (DA) as Rotex, polisher I’d maybe be careful with.
You may need to touch lightly, tilting the polisher ever so slightly - and with a DA polisher on presumably thin glass.. ai.. and the vibrations these provide..
Be careful and we might learn something her Alex - crossing fingers for success and learning something new! [wink]

I think I need to keep it as straight as possible in order to keep the glass straight and not create a lens effect. Been reading into it a bit now and they always warn for deformation of the glass. Our lens buddy above can agree.

I get the impression the Rotex with it's 600 RPM is way too slow, the dual action makes no difference. Everybody advises rotary in the range of 1500-2500 RPM.

I cross my fingers too, but I can do without this. I don't like to work with glass, it's too sharp. But I'm the only one who has the slightest chance of succes with this in this company. Not sure if that's a compliment or not.  [tongue]

 

[Cheese]

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

My  [2cents] ...the RAP with a 80 mm Polishing pad 488337, some Mirka 90 mm diamond paper and then some 90 mm sponges for the 3M glass polish. Maybe throw in a couple of 90 mm hard felt polishing pads also to keep things flat.

Keeping the polished area as small as possible will certainly speed up the process and keeping it as narrow as possible may visually hide any surface aberrations.
https://www.mirka.com/MI241D-DMD/

Here's something interesting, 3M offers both diamond lapping film and cerium oxide lapping film. I'd suspect the cerium oxide film is cheaper.
https://multimedia.3m.com/mws/media...lishing-film-for-precision-proc-finishing.pdf