How to Get Hard Water Stains Off Glass

posted Mar 7, 2010, 5:31 AM by Judah Clark   [ updated Apr 6, 2016, 9:14 AM ]
If you want to know how to get hard water stains off glass, you have come to the right place. There are many different products that can be selected to remove hard water stains off glass but to know which one to choose requires knowing what caused the stain in the first place. First, is it really a hard water stain?

There are about 5 different types of glass stains commonly found on glass surfaces
  1. Oils Based Stains
  2. Soap Scum Stains
  3. Mineral Stains
  4. Acid Burns
  5. Surface Scratches
The main difference in them all, in regards to restoration, is if what ever is causing the optical distortion/stain has damaged the surface of the glass or is just remaining on the surface and is difficult to remove. 

Typical Causes of These Types of Glass Stains

Oils Based Stains

  • Oily waterproofing over spray
  • Silicone or urethane caulk leaching
  • Leaching from paints or coatings 
Soap Scum Stains

  • Hard water and soap combine to cause scum
  • Window cleaning process using dish washing detergents

Mineral Stains

  • Leaching from unprotected precast or GFRC concrete
  • Contact with tap water such as sprinkler system over spray

Acid Burns

  • Cleaning with harsh acidic cleaners

Surface Scratches

  • Cleaning with harsh abrasive cleaners
  • Scrapers improperly used to remove debris

How to Remove Hard Water Stains Off Glass


Oil Based Stains 

Oil based stains do not damage the surface of the glass and can be removed with a product that breaks down and absorbs the oils from the surface revealing a perfectly clean glass surface. For this application we recommend Presto's Glass ReSurfacer Final Polish or EnviRestore Glass Stain Remover. These products can be used with a rag to gently scrub the surface of the glass and will remove any type of oils stains easily and quickly. These products contain no acids and no harch abrasives.

Soap Scum Stains

Soap scum stains cans be difficult to remove depending on how hard the hard water is and how long the stains have been allowed to build up on the surface. This type of stain and how hard it is to remove is in between a mineral stain (The hardest to remove) and a oil based stain (The easiest) because it's a mixture of minerals from the tap water and residues from soap. For this application we would also recommend Presto's Glass ReSurfacer Final Polish or EnviRestore Glass Stain Remover. These products can be used with a rag to gently scrub the surface of the glass and will remove any type of glass stains.

Mineral Stains

Mineral stains are the most difficult to remove because the minerals bond to the surface of the glass and create a tenacious bond to the surface. This is due to the fact that the stains are the same materials as the glass mainly silica, magnesium, and calcium. The best way to remove mineral type stains from glass is to sand the glass surface down to remove the stains and effected surface to reveal a completely brand new glass finish which sound more complicated than t really is. For this application we recommend Presto's Glass ReSurfacer Final Polish with a variable speed polisher and the Glass ReSurfacer Pad This product and process uses the same type of materials that are in the stains, and the glass surface to scratch the surface of the glass at a level that is undetectable with the naked eye, even under magnification.

Acid Burns

Acid burns are most commonly caused by the use of hydrofluoric acid. This type of product is most commonly used on glass to remove stains and it does work however about 25% of the time it burns the surface of the glass and causes the need to perform a second restoration step to remove the acid burns. Again, we would recommend  Presto's Glass ReSurfacer Final Polish with a variable speed polisher and the Glass ReSurfacer Pad. This process will sand the surface of the glass down including the acid etched or burned layers revealing a new highly polish and imperfection free finish on the glass surface.

Surface Scratches

Surface scratch can because by any type of abrasive materials that are harder than the glass surface. Sand is the most common reason for scratches and it is forced into the surface by means of items such as scrapers. Another common reason for surface scratching is harsh abrasive products used to remove stains from glass. How abrasive is too abrasive for glass? If you take a small mount of product on your finger nail and rub it against another finger nail you will feel the abrasiveness of the product. If it feels gritty and scratches the surface of your fingernail it will most likly scratch the surface of glass. Again, we would recommend  Presto's Glass ReSurfacer Final Polish with a variable speed polisher and the Glass ReSurfacer Pad. This process will sand the surface of the glass down including the acid etched or burned layers revealing a new highly polish and imperfection free finish on the glass surface. If the scratches are really deep and can be felt by rubbing your finger nail on the glass surface, we recommend a glass scratch removal system.