Method · Chemistry and quantities

Window cleaning solution

There is no secret recipe on this page — deliberately. The right solution for your job is decided by three things you can actually check: what the product label on your cleaner says, what is on your glass, and what your water is like. This guide shows how to plan around those three, and how to turn glass area into sensible quantities.

The label is the specification

Commercial glass cleaners differ in concentration, surfactant type and additives, which is why their labels disagree with each other — and why any one-size dose found on the internet is wrong for most bottles. Treat the label as the specification: its dilution ratio and application rate are the two numbers the calculator asks you to enter, and it will not invent them for you. If the label gives a range, start at the weak end; over-dosing is the classic cause of hazy, streak-prone glass that gets worse with every “stronger” attempt.

Washing-up liquid deserves its honest footnote: a small measured amount in water is a long-standing glazier’s wetting agent for plain glass, but it is unmeasured by design, and some of it carries hand-care additives that smear. If you use it, use little, and accept that you are outside any manufacturer’s specification. Kärcher’s window guidance discusses detergent restraint and the wet-then-remove workflow this site builds on.^[K]

Water quality decides how forgiving the job is

Most of a “detergent problem” is a water problem. Hard tap water carries dissolved minerals; whatever dries on the pane stays on the pane as spots and haze. In soft-water areas the same technique with the same product simply looks better. Three practical responses, in rising order of effort:

• Dry the glass before it air-dries — the squeegee-and-cloth discipline in the flagship guide.
• Work smaller sections in warm or breezy weather so nothing flash-dries mid-pane.
• Use purified (deionised or reverse-osmosis) water, which dries spot-free — the basis of pure-water pole systems described in the tools guide.

Quantity planning

Quantities are geometry, not intuition: glass area × your label’s application rate = solution volume, and the label’s 1:n ratio splits that volume into concentrate and water. The area & solution calculator runs exactly that arithmetic over your entered values, adds an optional planning margin of up to 25 %, and prints a plan record with the formula on it. Its worked example — 9.6 m² of glass, 10 % margin, an entered 50 ml/m² and 1:20 — exists to show the shape of the calculation, not to recommend those numbers.

Filmed, tinted and coated glass

Everything above assumes plain glass. Films and coatings are surface chemistry you did not choose and cannot see the specification of — so the film manufacturer’s care sheet outranks every general rule, including the ones on this page. The tinted windows guide shows how differently 3M and LLumar treat their own products, and what to do when the film cannot be identified.

Correction and version note: written for content contract 2026-08-20.2; sources accessed 2026-08-20. Corrections are recorded on the methodology sheet.