Expert: Robert Lamb - 2/18/2010

Question
the water has been hitting the windows for over 12 years and has never been cleaned off , i have tried scraping with a razor and this has only gotten some off i have tried kaboom and viniger and CLR and lime away and ducky spotremover do you have any more things i might use thank you , roger myer

Answer
Roger,

To remove hard water spots from glass, you will need to use a restoration method professional window cleaners use. The two methods are chemical and mechanical.

Chemical: The most effective method, and the one I would recommend, is to use a chemical or chemical formula (most are acid based). You can start at the milder end of the scale using something like Sani-Scrub, A1 Hard Water Stain Remover, Bio Clean Water Stain Remover, MDR, Unger RubOut, Safe Restore, Sorbo Hard Water Stain Remover, etc. With the damage you describe, you will probably need a harsh acid like hydrofluoric acid. This is extremely corrosive and dangerous to handle though. See the Wikipedia article at http://tinyurl.com/yhbura CC550 is one of these chemical formulas that contain hydrofluoric acid. When working with hydrofluoric acid, always read and follow the instructions and use safety goggles, gloves and avoid getting this on your skin.

There are window cleaning warehouses that sell these items especially for this purpose. We use ABC Window Cleaning Supply (http://tinyurl.com/ykl37gy), but there are other fine suppliers like J Racenstein (http://tinyurl.com/yfaeqdm).

The process is to put a small amount of chemical on a white pad (3M makes these) and put the pad on the glass in an out of the way area to test it on the glass. These scrub pads are graded according to abrasiveness and white is safe for glass.

Mechanical: This method is usually done by buffing off the glass using an abrasive like cerium oxide commonly called "jeweler's rouge". The process can be dramatically expedited by using a power buffer or drill.

I hope this helps. Please let me know if this has resolved the problem.

Sincerely,

Robert Lamb
Window Masters
www.mywindowmasters.com
Rob's Window Cleaning
www.robswindowcleaning.com