PROBLEM: Hard Water Stains
SOLUTION: Chemicals and Abrasives

Hard water stains occur when sprinkler water hits the building or rainwater travels over concrete or a precast surface of a building and carries tiny particles from that surface onto the window. After the rainwater dries the mineral deposits are very hard to remove. Acid rain and sprinkler stains are of the same nature due to the high concentration of minerals present in the water. Much like Oxidation, mild chemicals, abrasives and some scraper usage will take care of most problems.

PROBLEM: Oxidation
SOLUTION: Mild Chemicals & Abrasives

Oxidation, also known as etching, hazing or screen burn, occurs when metals around windows (frames, screens, etc.) are exposed to rain or humidity and deteriorate causing oxidation. This oxidation runs down the glass and penetrates (or clings to) the glass. Mild acids, like Crystal Clear 550, or abrasives like Sörbo Stain Remover (often combined with fine steel wool) are often all that’s required to remove the oxidation.

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Stain Removal and Window Restoration


To see all of these products in action, watch our video about window restoration with window cleaner Craig Aldrich on our video page


Mildest to strongest stain removers:

A1: A white, pasty product. Removes basic hard water stains, but will not remove silicate deposits. Basic stains include those made of calcium and magnesium. It may remove some oxidation stains, mild screen burns, and similar stain problems.

MDR: More of a liquid product, versus A1. Removes basic hard water stains, but will not remove silicate deposits. Basic stains include those made of calcium and magnesium. It may remove some oxidation stains, mild screen burns, and similar stain problems.

RubOut: A liquid/paste product. Similar in many ways to A1 and MDR. Removes basic hard water stains, but will not remove silicate deposits. Basic stains include those made of calcium and magnesium. It may remove some oxidation stains, mild screen burns, and similar stain problems.

Bio-Clean: A green, pasty product. Has a mild, gritty texture to it. Slightly tougher than the above three products. A popular product among window cleaners.

Sorbo Hard Water Stain Remover Powder: Pour powder on a wet white Scrub pad and apply directly to the glass. Just as you would any of the liquid paste/products above.

X-19: Oxalic Acid. One of the milder acidic cleaners. Not as strong as a Hydrochloric or Hydrofluoric Acid.

OneRestore: Hydrochloric Acid. Make sure you wear gloves with any type of harsher acid. Also deemed a restoration detergent. Sometimes, it is best to spray this product onto the glass. When you spray on the chemical, it helps keep the chemical in a concentrated area when working. This is a smart technique when working on hot conditions. You do not want to have these harsher chemicals dry on the substrate. Note: if used in this manner, beware of hazardous inhalation hazards.

CC550: Hydrochloric and hydrofluoric acids. Make sure you wear gloves with any type of harsher acid. Warning this will smoke/cook float glass. The chemicals in this product react with the tin in the glass. You can detect the tin/air side of the glass with a UV light, the digital tin detector or the Tin Side Detector Lamp. CC550 will work safely on the air side of the glass. It is recommended to test the product on a small area of the glass to make sure you will not "cook" it before applying this product to the entire window. You want to work relatively quickly with this product if you are in hot areas.


How to use these products:
  • Apply product to wet white pad and apply to glass in a circular motion. Work in 1 ft squares. You want to work relatively quickly with this product if you are in hot areas.
  • If necessary, you can also use a steel wool pad on the area, scrubbing the chemical into the glass After scrubbing with steel wool, use a scraper to remove the oxidation deposit from the window. Scraping gets below the stain. Since glass is a porous material, the longer the stain has been on the glass, the harder it will be to remove from the substrate.
  • Note: With glass that is poorly heat treated, be extra careful not to scratch the glass when scraping. Click here for more information about scraping. It is smart to have your customer sign a liability waiver before doing any scraping on a job-site. Click here for our scraping liability waiver

Variety is the key:

It is good to keep a few different types of stain removers in your truck. Sometimes, one product will work better than another on a specific project. Also, you can use a milder stain remover on the upper portion of the window pane - where the oxidation and silicate deposits are less concentrated - and use the harsher products only on the lower portion of the glass to remove the tougher stains.

A word on pricing your job:

When doing a stain removal job, remember you are not only cleaning the windows, but you are also restoring the glass to its original state. Remember, you are incurring the extra costs of the stain removal products and your time. You also have the skills and knowledge of how to remove these stains and the added liability of using these harsh chemicals on the glass. All of these are excellent reasons to charge a special fee for window stain removal and restoration. This isn't a simple, "straight" clean, so price your job accordingly.

In terms of liability: Click here for more information about scraping glass. It is smart to have your customer sign a liability waiver before doing any scraping on a job-site. Click here for our scraping liability waiver.

Frame restoration:

You can also offer the additional service of frame restoration to the customers. OneRestore is an excellent product to restore the window frames. Spraying the chemical on the window frame will help keep it from getting on the window panes themselves. Scrub in the chemical with a steel wool pad, rinse, and dry. Note: If spraying harsh chemicals, beware of hazardous inhalation hazards.