Good Window Cleaning Solution

Sam White

Sep 29

9 min read

Last updated: 29 September 2026

A good window cleaning solution combines purified water, a surfactant to break down grease and grime, and — for stubborn deposits — a targeted additive such as a light acid rinse or a solvent-based concentrate. For everyday commercial window cleaning, a small amount of professional-grade surfactant added to pure or deionised water gives streak-free results reliably; for heavily soiled glass or mineral-scale build-up, a specialist chemical treatment is needed before the standard wash.

Key takeaways

Pure or deionised water (typically below 10 parts per million total dissolved solids) is the single most important ingredient in a professional window cleaning solution — it leaves no mineral residue when it dries.
Professional surfactant concentrates are added at low dilution rates, often just a few millilitres per litre of water; more product does not mean better results.
Three broad solution types cover almost every situation: surfactant-in-purified-water (everyday cleaning), acidic descalers (mineral scale and hard-water deposits), and solvent-based or alkaline degreasers (construction residue and heavy grease).
The water-fed pole method uses purified water with little or no added chemical; the traditional squeegee method relies more heavily on a diluted surfactant mix.
Certain products — abrasive cleaners, bleach, ammonia-based glass cleaners — can permanently etch commercial glazing, sealants, and uPVC frames, creating liability for the building owner.
At Aston Maintenance, the combination of water quality and solution type is assessed before every job because mismatching either to the glass type or soil level is the most common cause of streaky results.

What makes a window cleaning solution "professional"?

A professional window cleaning solution is one formulated specifically for glass — meaning it removes contamination without leaving residue, attacking the glazing surface, or damaging surrounding materials such as uPVC frames, aluminium extrusions, or silicone sealants.

Domestic glass cleaners — the trigger-spray bottles widely sold in supermarkets — contain solvents and often fragrance that evaporate unevenly and leave films on large panes. They are designed for small interior surfaces, not commercial plate glass exposed to weather, pollution, and traffic film.

The distinction comes down to three things: water purity, surfactant quality, and the presence (or absence) of additives matched to the soil type. Professional products are also concentrated, making them cost-effective at scale.

Why is water quality the most important variable?

Tap water in much of the UK contains dissolved minerals — calcium, magnesium, silica — that remain on the glass surface as white spots when the water evaporates. The harder the local water supply, the more visible the deposit.

Professional window cleaners use water that has been filtered through reverse osmosis membranes, deionisation resin, or both. The target is a total dissolved solids (TDS) reading below 10 parts per million; at that level, the water evaporates cleanly without leaving a mark.

This is why the water-fed pole method — which uses purified water pumped through a brush to the glass — can, in principle, leave windows clean without any added chemical at all. The cleaning action comes from the mechanical agitation of the brush combined with the mineral-hungry nature of purified water, which actively attracts and carries away contamination.

For buildings in areas with very hard tap water, on-site purification units or pre-filled tanks are standard. The investment in water quality consistently matters more than the brand of detergent.

What are the main types of window cleaning solution, and when does each apply?

The three core solution types below cover the overwhelming majority of commercial window cleaning situations. Choosing the wrong one is the most common reason a cleaned window still looks dirty.

Solution type	Best for	Typical dilution	Key limitation
Surfactant in purified water	Routine maintenance cleans, lightly soiled glass	A few ml per litre	Ineffective on mineral scale or construction deposits
Acidic descaler (e.g. dilute citric or phosphoric acid)	Hard-water spotting, mineral scale, calcium run-off from concrete	Manufacturer's stated rate	Can damage stone surrounds and anodised aluminium if not rinsed promptly
Alkaline degreaser / solvent-based concentrate	Construction residue, paint overspray, heavy traffic film, silicone smears	Low dilution per instructions	Requires full rinsing; some formulas damage rubber seals

Surfactant solutions are the everyday workhorse. A good professional surfactant — sometimes called a window cleaning concentrate or squeegee soap — lowers the surface tension of the water so it sheets across the glass rather than beading, making it easier to draw off cleanly with a squeegee.

Acidic descalers are not used routinely; they are a targeted fix for a specific problem. If mineral scale has etched into the glass surface rather than simply sitting on top of it, no chemical solution will remove the damage — the glass will need mechanical polishing or replacement.

Alkaline degreasers are most common on first cleans of newly constructed or recently refurbished commercial buildings, where construction dust, silicone residue, and cement splatter are typical.

How do professionals actually mix and apply these solutions?

Following a consistent mixing and application process matters as much as the product itself. Here is the standard approach used on commercial jobs.

Test the water supply. Use a TDS meter to confirm the water source is at or below 10 ppm. If tap water is being used, confirm whether a purification unit is needed on site.
Identify the soil type. Look at the glass before mixing anything. White, chalky deposits point to mineral scale; oily smears or rainbow films suggest grease or silicone; general grey dullness is usually atmospheric dirt and pollution.
Choose and measure the solution. Use the manufacturer's stated dilution rate. More surfactant does not improve cleaning — excess soap creates foam that is difficult to remove and increases residue risk.
Pre-treat if needed. On heavily soiled glass, apply a specialist descaler or degreaser before the main wash, allow appropriate dwell time, then rinse thoroughly before the cleaning solution goes on.
Apply with the correct tool. For the traditional squeegee method: apply solution with a lambswool or microfibre applicator, then draw off with a sharp, undamaged squeegee blade. For water-fed pole: agitate with the brush using purified water; no squeegee is needed.
Rinse thoroughly. Any chemical residue left on the glass will attract dirt faster. Final rinse with purified water is standard practice.
Inspect in daylight or raking light. Hold a torch or step into a position where light rakes across the glass — residue and streaks invisible in flat light show up clearly this way.

Which solution works best for the water-fed pole method versus the traditional squeegee method?

The two main commercial cleaning methods use solutions differently, and understanding this distinction prevents unnecessary product spend.

Water-fed pole: The defining feature of this method is that purified water does the bulk of the work. A small amount of purpose-formulated, low-foam surfactant may be added to the tank for first cleans or particularly grimy glass, but on a regular maintenance schedule many operators use purified water alone. The pole extends from ground level — typically reaching up to four or five storeys — so the windows are rinsed and left to dry naturally without a squeegee.

Traditional squeegee method: This method depends on a surfactant solution to make the water sheet across the glass and slide smoothly under the squeegee blade. The concentration needs to be low enough that no foam builds up — experienced cleaners typically add a small dash of concentrate, not a full measure — but high enough that the water stays mobile on the glass long enough to be drawn off cleanly.

The two methods are not interchangeable: using a high-surfactant mix with a water-fed pole produces foam that cannot be rinsed away cleanly from a distance, and using plain purified water with a squeegee on heavily soiled glass gives insufficient lubrication.

For a detailed comparison of how these access and application methods work in practice on multi-storey commercial buildings, the guide on rope access and cherry picker window cleaning covers the access side of the equation.

What should you never put on commercial glass?

Some products that appear safe for glass are genuinely damaging on the commercial glazing and ancillary materials found on business premises.

Bleach (sodium hypochlorite): Effective at killing mould on soft surfaces but highly corrosive to the sealants between glazing panes and to the rubber gaskets in commercial window frames. It also fades anodised aluminium finishes.

Ammonia-based cleaners: Common in household glass sprays, ammonia attacks tinted and coated glass — including solar-control and low-emissivity (Low-E) glazings that are standard on modern commercial buildings. Damage to these coatings is irreversible.

Abrasive powders or pads: Scratch commercial glass permanently. Even a superficially light abrasive leaves micro-scratches that catch dirt and are visible in direct sunlight.

Undiluted acid: Even professional descalers can etch stone window surrounds, concrete sills, and anodised frames if left in contact too long. Always follow dwell times, and test on an inconspicuous area first.

Washing-up liquid (domestic): Not dangerous, but problematic — it contains added fragrance, dye, and salt that leave films on large glass surfaces and attract dust quickly after cleaning.

For small business owners, the practical risk is using a product a member of staff has sourced without specialist knowledge, damaging a glazed façade, and facing a repair bill that far outweighs any saving on professional cleaning. The existing article on what causes streaky exterior windows covers several of these product-related causes in detail.

Does the type of glass affect which solution you should use?

Yes, and this is where many generic cleaning guides fall short.

Standard float glass: Compatible with most professional surfactants and, when needed, correctly diluted descalers.

Tinted or solar-control glass: Avoid ammonia-based products and strong solvents. Check manufacturer guidance before using any specialist chemical.

Low-E (low-emissivity) glass: The metallic coating is on the internal surface and is not directly cleaned, but if the unit seal has failed and moisture has entered the cavity, no external cleaning solution will resolve the haze — the unit needs replacement.

Self-cleaning glass (e.g. Pilkington Activ): Designed to break down organic contamination with UV light and sheet off with rain. Professional cleaning with standard surfactant solutions is compatible, but acidic products can disrupt the titanium dioxide coating. Check with the glass manufacturer.

Tempered or laminated glass: No special solution requirement, but avoid abrasive tools entirely — any surface scratch is permanent and structurally undesirable in safety glass.

At Aston Maintenance, our approach across commercial properties in Oxfordshire, Buckinghamshire, London, Warwickshire, and Northamptonshire is always to confirm the glazing specification before selecting a treatment — particularly on recently refurbished or newly constructed buildings where solar-control glazing is increasingly standard.

Frequently Asked Questions

What is the best homemade window cleaning solution? A small amount of washing-up liquid diluted in warm water works for interior domestic glass but is not suitable for large commercial panes — the fragrance and salt content leave films that attract dust quickly. For any commercial property, a purpose-formulated surfactant concentrate in purified water will consistently outperform DIY mixes.

Can I use vinegar to clean commercial windows? Diluted white vinegar (acetic acid) is mildly effective on light mineral spotting on domestic glass, but it is too weak for commercial-scale hard-water deposits and too unpredictable near stone surrounds, anodised frames, or specialist coatings. Professional acidic descalers are pH-calibrated and buffered for safe, controlled use on commercial glazing.

Why do my windows look worse after cleaning? The most common cause is residue from the cleaning solution — either too much surfactant, a product not suited to large glass surfaces, or a rinse with hard tap water that has left mineral deposits. Streaks visible in raking light are almost always a water-quality or dilution issue rather than a technique failure.

How often should commercial windows be professionally cleaned? The right frequency depends on the building's location, glazing type, and the impression the business needs to make. Town-centre retail and client-facing offices typically need cleaning every four to eight weeks; industrial units in less exposed positions can go longer between cleans. The article on contract cleaning for small businesses covers how to build this into a maintenance schedule.

Is purified water safe for all window frames and surrounds? Yes. Purified water carries no minerals or chemicals that could react with uPVC, aluminium, timber, or stone. It is one of the safest rinse options available, which is why it is the final step in professional water-fed pole cleaning.

What concentration of surfactant should I use for window cleaning? Follow the manufacturer's stated dilution rate, which is typically a few millilitres of concentrate per litre of water. Adding more product than instructed increases foam, makes rinsing harder, and leaves more residue — it does not improve cleaning performance.

Can a window cleaning solution remove paint or silicone from glass? Standard surfactant solutions will not remove paint overspray or cured silicone. These require a targeted solvent-based product applied with care and in some cases mechanical removal with a specialist razor blade tool. This type of first-clean or post-construction clean requires a professional assessment rather than an off-the-shelf product.

Do self-cleaning windows still need professional cleaning? Yes. Self-cleaning glass (such as Pilkington Activ) reduces organic contamination through a UV-activated coating and shedding action in rain, but it does not remove traffic film, bird fouling, or mineral deposits from hard water. Periodic professional cleaning with a compatible, non-acidic solution keeps the coating functioning correctly.

Author: written by the team at Aston Maintenance, a family-run property maintenance company with over 25 years of experience in commercial and residential cleaning across Oxfordshire, Buckinghamshire, London, Warwickshire, and Northamptonshire.