Wally the Window Washer
washes windows for domestic and commercial customers in and around Pershore
Wally is: * regular * reliable * fully insured

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Pure Water
Pure water is the best cleaning agent for glass for two very good reasons.

• First of all, pure water is an excellent solvent. It will dissolve most minerals and all organic compounds that are likely to contaminate a window.
• Secondly, when pure water evaporates, it evaporates completely and leaves no spots or smears behind.

Have you ever breathed on a pair of glasses or on a mirror to clean the surface? Did you notice how clean the surface polished up and how the moisture dissolved even grease from finger marks? If you have, you have experienced the cleaning power of pure water.

The moisture that condensed from your breath was absolutely 100% pure - and it was this pure water that dissolved all the contaminants on the surface so you could polish them away.

It is the purity of the water that makes it such a good cleaning agent.  Pure water is a very powerful solvent, and will dissolve almost all minerals and organic compounds to some extent.

Here's a experiment you can try for yourself.

1 - Take a small mirror and clean it by breathing on it and wiping away the moisture with a clean cloth or tissue.

2 - Put the mirror in the fridge for a minute or two.

3 - take it out of the fridge and breathe heavily onto the the mirror so you get a lot of condensed moisture.

4 - Leave it to dry naturally.

Notice how the mirror dries perfectly clean. The moisture evaporated and didn't leave any residue behind.The moisture that condensed on the glass surface came from water vapour in your breath - and it was 100% pure water with absolutely zero mineral content. It evaporated leaving the glass surface absolutely spotless.

To summarise: These two things are the secret to cleaning with pure water:

1 - Pure water is an excellent solvent and either dissolves or washes away contaminants from a glass surface.

2 - Pure water evaporates and doesn't leave any residue.

Very pure water is found in nature in raindrops and in dew - and both are made by condensing water vapour. All other liquid water found in nature, standing or flowing, is impure to some extent. This is due to the pure rain or dew water (i) dissolving minerals as it passes over soil or rocks or passes through the Earth and (ii) dissolving organic materials. This water also has solid contaminants suspended in it in the form of very fine dust and microbes.

The water used for window cleaning is the same grade of water used in hospitals, pharmaceutical laboratories and research laboratories for cleaning glassware.

It usually purified using a process called reverse osmosis - of which more later. This is a much cheaper method of purifying than distilling.

It's probably easier to understand by seeing it rather than reading about it, so here's a video from YouTube of cleaning conservatory windows.

There are FOUR things to notice about the way that he works:

1 - He cleans the entire window including the frame and the sill.

2 - He is very careful to rinse the window well after the washing. A thorough wash followed by a careful and complete rinse is the key to success with a water fed pole.

3 - He is using a fairly low water flow - probably about 1.5 litres per minute.

4 - He leaves the windows to dry naturally. Because the water is pure and doesn't contain any dissolved minerals, the windows dry to a perfect, spotless and streak-free finish.

The brush is mounted on a pole so even high windows can be cleaned from the safety of the ground. Here's another video showing a news report about this system. It shows Terry Garbett from Kidderminster working on a house and an ancient building in the centre of Kidderminster.

It also gives a very concise and accurate explanation of how the system works and implications for safety.

The pure water is  pumped from a tank to the brush. It is then brushed onto the window frame and glass where it quickly loosens and washes away any surface dirt and dust. Difficult and tenacious contaminants like bird lime and finger prints are removed by gentle scrubbing with the brush. Then the brush is held away from the glass and the water sprays onto the window and rinses the surface. The window dries absolutely spotless - since there are no dissolved solids to leave spots!

The water is stored in a large tank either mounted in a van or a trailer or plastic barrels in a trolley-based system. The flow rate is usually between 0.7 and 2 litres per minute.

Finally, here are two videos from manufacturers of water fed pole systems.

This first one is an excellent video from the Window Cleaning Academy.  It is about the system developed by Ionics - a very large and go-ahead company. The basic technology, however, is universal in pure water cleaning.

This second video is from Puraqleen - a German company specialising in larger, commercial cleaning solutions. All the examples shown in this video are of large commercial jobs.

You probably know that the water delivered to your tap can be soft or hard, depending on where you live. Most of the UK has hard water. The hardness is due to dissolved minerals which water picks up as it percolates through the Earth's rocks into the aquifers. These are referred to as dissolved solids. Rainwater is very soft since it hasn't picked up any solids as it hasn't yet percolated through the Earth. This is why it is so good for washing your hair!

The water purity is expressed in parts per million (ppm) of total dissolved solids (tds).

Tap water is typically between from 60 ppm (soft water) to 200 ppm and above. Pure, uncontaminated rainwater will typically be between 2 and 6 ppm due to it catching dust as it falls through the atmosphere.

Water used for window washing is 0 ppm tds.

Tap water is purified, usually in five stages:

stage 1 - particle filter

stage 2 - carbon filter

stage 3 - carbon filter

stage 4 - reverse osmosis (RO) unit

stage 5 - de-ionisation (DI) unit.

Sometimes, in very hard water areas, a water softener is used before the standard filter.

When two water (or other solvent) volumes are separated by a semi permeable membrane, water will flow from the side of low solute concentration, to the side of high solute concentration. The flow may be stopped, or even reversed by applying external pressure on the side of higher concentration. In such a case the phenomenon is called reverse osmosis.

If there are solute molecules only in one side of the system, then the pressure that stops the flow is called the osmotic pressure.

Reverse Osmosis (RO) was invented in 1959 by Prof Reid of the University of Florida, and was put into practical use by Sidney Loeb and Srinivasa Sourirajan. It is a process which removes both dissolved organics and salts.

Feedwater is pressurized and flows across a membrane, with a portion of the feed permeating the membrane. The balance of the feed sweeps parallel to the surface of the membrane to exit the system without being filtered. The filtered stream is the permeate, because it has permeated the membrane. The second stream is the concentrate because it carries off the concentrated contaminants, rejected by the membrane.

Because the feed and concentrate flow parallel to the membrane and not perpendicular to it, the process is called “cross flow filtration”.

Depending on the size of the pores engineered into the membrane, cross flow filters are effective in the classes of separation known as Reverse Osmosis, nano filtration, ultra filtration and micro filtration.

Cross flow membrane filtration allows continuous removal of contaminants which in normal flow filtration would blind (plug) the membrane pores rapidly, in conventional systems. (GrahamTek changed this technique successfully)

RO removes most organic compounds and up to 99% of all ions.

This information is taken from:  www.bionicsro.com/what-is-reverse-osmosis.html.

• There are no agressive chemicals used in the cleaning process - only pure water
• There are no aggressive chemicals used in the purification process.
• The purification process uses very little energy.
• There are no harmful by products created by either the cleaning or the purification process.

Many of those who use rainwater claim that it is even better than purified water for cleaning, though there is no known scientific reason why this might be so.