If you suspect fabricating debris, check for parallel scratches. If you bring along a magnifier and check in bright light, often you can find smaller, invisible scratches parallel to the more visible scratches. These parallel scratches start when the scraper encounters a suitable defect, and tend to end where the scraper stopped. Be sure to check out the "Field Identification of fabricating debris scratches" information on the IWCA site. Dan Fields has some great info on his site.

As for whether the glass is tempered, sometimes the tempering mark is hard to see. There can also be problems with excessive fabricating debris defects on heat strengthened glass. Heat strengthened glass is processed in a tempering furnace, only cooled more slowly than tempered glass. Since heat strengthened glass is not safety glass, it doesn't have to be marked - and maybe that's what you're dealing with. By the way, this is why your "tempered glass" scratch waiver shouldn't say "tempered"; it should say "heat treated" to cover both kinds.

Gary Mauer
Window Cleaning Network - Oconomowoc, WI

If the glass is located in a safety area (tempered glass location) and you used a razor or scraper, it might be a surface defect. If this is the case, don't be surprised if the homeowner calls you back on a bright and sunny day with more scratches. Hopefully not.

Dan Fields
Fields Construction Services Inc. - Livermore, CA

To my knowledge, there is no way to determine exactly how a scratch was first caused simply by looking at the scratch itself. Yes, one can assume certain things based on past experience. For example, isolated scratches caused by sandpaper along the edges of a wood window. But, for a moment, let's focus on two or more scratches in the center of a window. How exactly do you tell if these scratches were caused by a "fabricating debris defect" or some other type of indenter? To date, there are absolutely no exact characteristics that would identify one from the other.

Paul West, Operations Manager
Extra Clean Inc - Nantucket, MA

Wrong. Look under a microscope. If there is a bump where the scratch begins, then the defect was caused by the fabricating debris, not the razor. This is a FACT!

Ron Friman
Expert Window Cleaning – Hawaii - Chicago, IL

For some, that's still not enough evidence to "prove" what actually caused the scratch. Some still believe maybe the mysterious debris could have come from another source. But if necessary you can go one step further and have a composition analysis done on the "bump" and find out it has the exact same composition as the glass substrate itself, which would suggest it is from the seaming process prior to heat treating the glass.

Ren Bartoe stated this in his 1999 US Glass article, "Maximizing Ceramic Furnace Roll Performance". Anyone can read the original article and clearly see he used the word defect many times, which means it shouldn't be there if all the proper standard fabricating procedures are followed. Years ago I contacted US Glass magazine to get reprints of that article. They advised me it would run $1.00 a copy. I replied, "Send me 2000 copies" and I've been handing them out ever since. Now the article is on the Internet, free for all to see.

Dan Fields
Fields Construction Services Inc. - Livermore, CA

Acid is some serious stuff no matter your skill level or how long you have been using it. Accidents can happen. For me it's all about Glass Renu.

Billy Templeton
Veterans Window Services - Phoenix, AZ

The main difference with using acid (when you can) is its speed. If acid will work, use it, but know the downfalls regarding personal dangers, glass damage, window frames, the facade and other possible surrounding damage. Hard water spot removal is a specialized area for window cleaners and always requires "testing" and you can never tell what will work and what won't without testing first. I don't know how anyone submits a proposal for water spot removal without extensive testing. With that being said, if you are dealing with the "tin side" of the glass, you might want to consider polishing off the water spots if that works quickly enough. If not, test an HF (hydrofluoric acid) product.

If the HF removes the water spots and you get "tin etch haze", you can usually polish off the etch with a quality polishing compound. This involves an additional step, but if it gets the job done, you just need to charge for the extra step.

Dan Fields
Fields Construction Services Inc. - Livermore, CA

Most rotary machines are designed to remove scratches on glass. A scratch takes up a small area and requires movement over a very small area of the window pane. Hard water deposits generally cover the whole window pane. To grind off such a large area requires a lot of time and elbow grease. You also have some concern with light refraction. Anything you do to the surface of glass will change the light refraction and may be visible when you are done. However I have had some good results with an SRP machine.

Gordon Knopp
Squilchuck - Ephrata, WA

A quality polishing compound should not leave any light refraction that would show any different than the unrestored area. The only exception to that statement would be in a high humidity area, such as a spa or shower area. The steam from these type areas contact the glass surface, it would show the areas that were polished. If this becomes an issue, apply a quality glass sealer.

Dan Fields
Fields Construction Services Inc. - Livermore, CA

Be very careful using any acids or chemicals on coated glass. If you're actually working on an exposed pyrolitic coating, I would not take that job. If your client "says" they just want to make it look better than it looks now and "says" they don't care "if" the coating doesn't come out perfect that means nothing. You MUST get that in writing.

Dan Fields
Fields Construction Services Inc. - Livermore, CA

I'd recommend OneRestore with either a white pad or sponge. Check the initial application to see if there are any side effects to the paint on those frames.

Craig Aldrich
Sparkle Window Cleaning - Canyon Lake, CA

OneRestore may work; Eacochem also has a product called Cleansol that may work better on painted frames. I just tested both products on older painted frames and Cleansol worked a bit better. They are made by the same company and if you call them, they can give you guidance.

Dan Lloyd
Red Wagon Cleaning Service, Inc. - NC

If these are actually powder coated, they only appear to be painted. That is the case with most of the colored, mass produced aluminum frames you see. Nutshell explanation of powder coat is that a powder is applied in production, which is then melted and cured. Powder coat looks like a perfect paint job - no runs, no brush marks, no sagging. (Paint tends to look like it was painted on.) That powder coat is tougher than paint, but it, too can be damaged by steel wool or an abrasive powder. Sulfuric acid will damage the powder coat, but milder, weaker acids should not.

Even though the coating may be unaffected by what you try, any acids could cause cut ends of the frame and interior components to corrode. I would test the mildest formula that will remove calcium safely. Plan on rinsing thoroughly with copious amounts of water. Fortunately, calcium carbonate (lime) is one of the easiest mineral deposits to remove, so your prospects of using a milder acid formula are good. Test a less vigorous product with less hazardous ingredients such as phosphoric acid, sulfamic acid, citric acid or acetic acid (vinegar.) Other than calcium you're sure of, there may be other, more difficult to remove mineral stains on those frames. You could remove all of the calcium deposits very easily with one type of acid and still be left with some other mineral stain that won't budge.

If you get all of the calcium carbonate with something like acetic acid, and there are other stains remaining, there's no need to keep reapplying the same product. You would need to test another product on the remaining stain. (Or in the case of frames, maybe just let it go.)

Gary Mauer
Window Cleaning Network - Oconomowoc, WI