Buildup or contamination seem most likely to me: I understand silicate deposits are hard enough to scratch glass – and calcium carbonate is not. It's not the metal wool - I understand steel wool can start to rust while you use it, some chemicals cause steel wool to rust faster – and rust is harder than glass, so it could be rust. But you use the same chemical with bronze wool, and bronze wool doesn't rust. So unless your chemical already contains abrasives, it's not the chemical.

Something is/was different at times when you notice this problem. If you can figure out what's different, you ought to be able to control that. Some theories are harder to test - you couldn't prove it was a buildup of silicate deposits unless you had samples to test. But you could easily prove whether or not a metal wool or chemical causes scratches simply by testing them on unscratched, uncoated windows in your own home or office – or just buy some glass from a hardware store or glass shop. Unless it happens for you every time - with or without chemicals – then it's not the metal wool.

Gary Mauer
Window Cleaning Network - Oconomowoc, WI

I believe the scratching is a result of the actual water spot material, not the steel wool. Steel wool is much more aggressive than white pads and can remove the water spot damage much faster, but dislodges large pieces of water spot buildup, which I believe scratches the glass surface in the process.

It's not always the tool, in spite of what you hear. When rusty steel wool or a rusty razor blade scratches the glass, it's the rust, not the metal that's doing the scratching. If you're using wet steel wool on any glass (tempered or annealed), the wool won't scratch. If you use it on heat-treated glass that has surface defects from excess fabricating debris, it still won't scratch the glass, BUT the fabricating debris defects might. I have done a lot of testing on stained glass samples. I have concluded some glass restoration projects are a two-step process. I would suggest staying with the white pads, take a little longer and finish off with a polishing compound solution.

Anyone entering the world of water spot removal must realize "every" water spot is different and depending on the composition of that water spot, it will require different solutions. I tell my clients every water spot can be removed, it's just a matter if the client is willing to pay for the restoration required. We set a few ground rules. We do not offer any type of glass restoration on coated glass. We also get a "No Fault" glass breakage waiver. This protects us from any glass breakage, since we cannot guarantee the quality of the glass behind the frames. If the glass has chips along the edge, it is very sensitive to breakage when put under stress during restoration.

Dan Fields
The Fields Company - Livermore, CA

We have some small retailers that will still fax and one big facility manager that still faxes.

Doug Koliboski
Your Window Cleaning Company - Cincinnati, OH

I don't even have my fax machine hooked up any more. Everything is done through email.

Wes Buckner
Mid-Ohio Window Cleaning - Galion, OH

We have not even had a land line in 7 years, let alone a fax machine.

Jeff Scott
Green Window Cleaning, LLC - Sun Prairie, WI

Be careful when you do prison windows. They are made completely out of plexi. Make sure to tell the GC and have the painters clean up their own work.

David Levitt
The Glass Cleaners - Raleigh, NC

Standard "bullet" resistant glass is just several layers of laminated glass, so no problem with standard cleaning. But some also has a plastic layer on the inside surface of the building, which you might want to be extra careful not to scratch. This extra plastic film is applied to reduce or eliminate spalding of glass shards onto the occupant, if a large caliber gun is employed.

Dan Fields
The Fields Company - Livermore, CA

There are many different types of Bullet Resistant material on the market today, everything from layered laminated Glass to cast acrylic to polycarbonate to layered combinations of all three. Most Bullet Resistant material installed today will have Poly, acrylic or plastic coating on the inside surface that will scratch with normal cleaning methods. Your first step would be to find out the material you are dealing with and then move forward from there. I would recommend new Micro fiber rags and pure water. If you should scratch the Bullet Resistant material, be prepared for a replacement cost starting at $1000.00 per panel.

Troy Nelson
Xtreme Cleaning - Janesville, WI

I sometimes struggle to convince customers who have had a bad experience with waterfed to use my services, but once I have completed a clean they have been more than happy. The rinse is the most important part of the clean. The first clean is the most important to get right and is worth spending extra time on. I usually charge an extra 50% on the normal price and explain the reasons why.

This is the way I find works best for me for first clean(s):

Scrub the tops of frames including around the filters/vents, then give a good rinse.
Scrub the rest of the window and rinse from the top of the glass (not over the top of the frame).
Move on to the next windows on that level and do the same.
Once the windows on that level are completed I go back to the beginning and rinse again. If the glass has completely dried I sometimes give them a very quick scrub - literally a couple of seconds to remove any water marks or runs that may have been left.

I usually do this for the first 1 to 3 cleans. After this I leave out the second rinse.

Andrew Giles
Mr. Squeaky Clean Ltd - Cambridge, England, UK

Water-fed pole systems can be great and save a lot of time in some situations, though they will never match getting hands-on. I do agree that the more time and effort you put into it, as with any method, the better your results will be. I do recommend having a water-fed system, if you are doing an ample amount of various work on which to use it. If you have a small company, and only want it to help save time, your results may not always be what they should be for a good reputation of quality. As with anything, proper application and effort is what it takes to ensure quality.

Jason Haas
Paneless Window Cleaning - Naperville, IL

I've been using the R.O system in the UK since 2002 and have great results. The system works best on UPVC (vinyl) frames or any window units which are not porous. Badly painted wooden frames will release dirty water back on to the pane and create terrible streaking. Well painted wooden frames are not a problem. In strong direct sunlight I have to rinse more to ensure the dirt leaves the pane and does not dry on.

Mark Williams
WilliamsCLEAN - Preston, England, UK

I am in New England and do strictly residential. I use a waterfed pole system every day without a problem. I wouldn't leave home without it. There is a bit of a learning curve with it but as long as you cover the whole glass on the scrub and rinse you shouldn't have a problem, provided the filters are in good working order.

Tom Spitz
Clearview Window Washing - Rockville Centre, NY

Although I'm on the con side of WFP vs. hands on debate, it definitely has its uses when no other access can be achieved safely. I've been using a 60' Unger Carbon Fiber system since 2007. I have to admit that thanks to my WFP the days of renting monster 50' & 60' ladders are long gone. We don't have restrictions in the US but some major corporations with safety officers on site and some construction sites absolutely won't allow them. 80% of the time they want lifts not waterfed due to the mess, hoses, water use ($) and of course quality. I love this debate; it shows how passionate window cleaners are about the trade.

Robert Lang
L.A. Window Cleaning LLC - Holbrook, MA