By : XO2® Pty Ltd, David Blamire March 15th, 2017

Here’s How To Remove Hard Water Mineral Stains On Windows And Glass

Hard water stains are often confused with soap scum that doesn’t wash off. The easy way to tell whether the window has a mineral stain is if a regular cleaning detergent does not have any effect on it. Hard water stains can appears as droplets or a general haziness on glass. They can appear white through to a reddish brown colour in some instances. Since it is near impossible to clean off hard water staining with regular cleaning methods, we’ve prepared a guide to help you remove these types of stains from windows and glass.

What you need to know

Before we get into the guide, here is some essential information that you need to know:

A. What causes hard water stains?

• Spots of water left to dry on shower screens or glass windows. Solution: Squeegee dry immediately.

• Sprinkler systems spraying hard water onto glass. Solution: Move sprinklers.

• Hosing concrete paths where lime bounces up onto glass. Solution: Seal concrete.

• Lime leaching out of cement from buildings onto glass. Solution: Seal concrete.

• Silica leaching out of seals onto lower sheets of glass. Solution: Not much you can do.

• Iron leaching out of metal fly screens onto glass. Solution: Replace the screens with nylon.

• Reddish bore water stain buildup from hosing glass. Solution: Don't hose glass.

• Iron stains from roofing. Solution: Install effective guttering.

B. How to prepare for hard water stain removal

• Always do a test or demonstration to assess suitability and the potential success of the procedure.

• Never try to remove hard water stains in direct sunlight or from hot glass.

• Windows should always be thoroughly cleaned before removing any stains.

C. Precautions for removing hard water stains

• Sometimes hard water stains will look severe, but can be removed relatively easily. Other times the stain will look minor, but can be impossible to remove. Do not judge a hard water stain by the way it looks.

• Only use non-abrasive white scrubbing pads. Test the scourer first to ensure it is suitable.

• Scrubbing the stain remover in all directions is a must. In many cases a right handed person can have different success to a left handed person (and visa-versa) just because of the direction they tend to scrub in.

• Do not allow the stain-removal solution to dry or sit on the window frames. Wash immediately.

• Do not let the cleaning product dry on glass.

• Be aware of other surfaces that may come into contact with the chemical. This is particularly important for stone and metal surfaces. For example, if you are removing a hard water stain from a shower glass panel and the surrounding tiles are marble, you will need to protect them from the chemicals to prevent etching.

The cleaning guide

Now that you have got all the information you need, it is time to do some cleaning.

A. What you need.

• Hard water stain remover

• Container for the mixed paste

• White super-soft scourer

• Window cleaning kit including squeegee and washer

• Bucket and water

• Rags and cloths

• Gloves and personal protective equipment

Optional: Mechanical action can be helpful. On each particular job you can first test if a hand-held slow-speed polisher / scrubber delivers better results. Ensure the paste does not dry and the process is suitable for the glass you are working on.

B. How to remove hard water mineral stains on windows and glass.

1. Prepare the equipment.

2. Wash the windows. Scrape any debris and then use a window washer and squeegee to clean and dry.

3. Apply the hard water stain remover as a thin paste to small areas via a suitable scourer.

4. Continue to scrub that area for at least 3 minutes in different directions before washing again with the window washing solution. Scrub north and south, east and west, left and right, clockwise and anticlockwise. Trust us, on many types of glass this with make a big difference.

5. Check to see that the stain is removed or improved and repeat the procedure if necessary.

6. Do not allow the stain removing solution to sit on window frames. Continue to wash off with water.

7. Wash area thoroughly with water.

8. For large or difficult areas of stains use a circular pad on a battery or air-operated drill.

9. Repeat the above process if necessary.

Important: Hard water stain removal is not a perfect science. Sometimes the results may be extraordinary, and other times it may not. When it comes to mineral stain removal there such thing as permanent damage to the glass. Sometimes hard water staining can not be removed and in these cases it might be worth thinking about replacing the glass or calling your insurance company to see if they will cover the damage.

How to quote for the job

Hard water stain removal is a specialty process and can sometimes be hard work. It is not part of a normal window cleaning service. The stain removal process is often quoted as a percentage of the replacement cost of the glass.

Demonstrations are essential for contractors to understand the work required and how they should quote. It is also good for the client to see the results they can expect. If you choose to do this yourself for the first time, please understand there is a learning curve. Hard water stain removal is also very different depending on where in the country you live and work.

As a supplier of product that removes hard water stains, we do not ever guarantee any results. The possible variables (eg. glass type, glass porosity, mineral type) are too many to account for. And we suggest that you also make no guarantees to your customers without thorough pre-testing and demonstrations on more than just one part of the area to be cleaned.


In most cases you can achieve great results with a high quality hard water stain remover and the right process. As you gain more experience with these methods you can expect to get even better results.

If there is no improvement after persistent application of this procedure, the surface may be beyond repair and the replacement of the glass may be necessary. Hard water stains can be costly and that’s why regular and effective glass maintenance is so important.

We’d love to hear any tips or tricks you’ve found successful on hard water stain removal for glass and windows. Get in touch with your thoughts, ideas experiences.

Feel free to call our customer care team on 1300 123 499, if you require any help or advice on window cleaning equipment and hard water stain removal products. For more information you can also visit the XO2 cleaning chemistry and supplies online store.

Happy glass cleaning!