In a nutshell
- 🧪 Cornflour/cornstarch is the secret ingredient: microscopic starch granules polish glass, bind oils, and reduce surface tension for a true streak‑free finish.
- 🔍 Beats soap and vinegar alone: reduces residue from surfactants, evens evaporation, and cuts dust‑attracting static for longer‑lasting clarity.
- 🥤 Simple DIY mix: ~400 ml water (preferably distilled), 100 ml white vinegar, 1 tbsp cornstarch, optional 1 tbsp isopropyl alcohol; shake before each use.
- 🧼 Pro technique: light misting, two‑cloth method, avoid direct sun, fold edges for seals, use a squeegee on large panes, and pre‑dust to prevent micro‑scratches.
- 💷 Budget‑friendly and low‑tox: costs pennies per batch, safe for modern glazing, better indoor air than perfumed sprays, and delivers sharp, “new‑window” brightness.
Glass cleaner aisle looking a bit dear? Save your quid. The most effective weapon for truly streak‑free windows is hiding in your baking cupboard. In the UK it’s sold as cornflour; in the US you’ll know it as cornstarch. This humble powder doesn’t just clean. It polishes. It lifts greasy fingerprints, breaks the filmy residue that standard sprays leave behind, and leaves panes gleaming in natural light. No harsh fumes, no sticky finish, no disappointment when the sun hits. It’s the quiet, kitchen‑shelf upgrade that turns cloudy glass into crisp, camera‑ready clarity. Here’s how it works, why it outperforms pricier formulas, and the easy recipe you can mix in minutes.
The Secret Ingredient: Cornstarch (Cornflour) Explained
Cornstarch doesn’t behave like soap. Each microscopic starch granule acts as a gentle, non‑scratching polishing bead. As you wipe, those particles slide across the glass, disrupting the thin film of water and detergent that usually dries into tell‑tale streaks. The granules also bind to oils from fingertips and cooking vapours, so grime lifts cleanly rather than smearing from one corner of the pane to another. That’s why the finish looks sharper, brighter, and less hazy than with ordinary blue sprays.
There’s chemistry at play. Starch modifies surface tension, encouraging water to break and evaporate evenly instead of drying in uneven sheets. It also leaves virtually no glossy surfactant residue, which is what often catches sunlight and highlights swirls. Better still, it’s safe on modern double glazing and mirrors, and it costs pennies per batch. Use it on patio doors, shower screens, glass balustrades, even glass oven doors after a cool‑down. One caution: starch settles. Shake your bottle before each use to resuspend the particles and keep that flawless, low‑haze finish.
Why Cornstarch Beats Soap and Vinegar Alone
Standard washing‑up liquid excels at cutting grease, yet its leftover surfactants cling to glass. They’re invisible indoors until a shaft of daylight turns faint lines into glaring streaks. Vinegar is a classic, and for good reason: acetic acid dissolves limescale and mineral spots from hard water. But vinegar alone can still dry patchily, especially in warm rooms or direct sun. Cornstarch bridges that gap, turning a good cleaner into a great finisher.
By adding a pinch of starch to a water‑and‑vinegar base, you introduce three upgrades in one go. First, mild mechanical polishing that removes the micro‑film responsible for haze. Second, a more even evaporation profile, so you don’t chase drying marks around the pane. Third, fewer static issues; glass wiped with starch tends to attract less dust immediately afterward. The result? A clean that looks “new‑window” bright for longer. It’s low‑tox, fragrance‑free, and ideal for homes with pets or toddlers pressing hands and noses to the glass. It’s also cheaper per litre than most branded formulas, without the colourful dyes or sticky additives that cause streaks in the first place.
How to Mix a Streak‑Free Cornstarch Cleaner
Make a small batch you’ll actually finish. Use warm water to disperse the starch, then shake before every spray. Keep the recipe simple and consistent; precision equals repeatable, streak‑free results.
| Ingredient | Amount | Role |
|---|---|---|
| Warm water (preferably distilled) | 400 ml (1⅔ cups) | Dilutes and reduces mineral spotting |
| Distilled white vinegar | 100 ml (⅖ cup) | Dissolves limescale and soap film |
| Cornstarch / cornflour | 1 tablespoon | Polishes and prevents streaks |
| Isopropyl alcohol (optional) | 1 tablespoon | Speeds evaporation, great for mirrors |
Method: add water to a spray bottle, whisk in cornstarch until smooth, then add vinegar (and alcohol if using). Label and shake. Lightly mist glass; don’t drench. Wipe with a clean microfibre cloth in vertical strokes, then horizontal passes. Finish with a dry edge‑buff around seals and corners. Avoid hot glass and direct sun that flash‑dries cleaner into marks. For heavy grime, pre‑wipe with damp microfibre, then use the starch mix for the final brilliant pass.
Pro Techniques for Crystal‑Clear Panes
Timing matters. Clean on a cool, cloudy day, or early evening, so the solution doesn’t evaporate mid‑wipe. Dust first with a dry microfibre; grit scratches and sabotages shine. Less liquid equals fewer streaks; mist lightly and let the cloth do the work. Use one cloth to apply, a second perfectly dry cloth to buff. Reserve a third, labelled “glass only,” to keep fabric softener residues away from your panes.
Struggling with edges? Fold your cloth into firm squares; crisp edges track along seals without smearing onto frames. For panoramic windows, a squeegee is unbeatable: pull in overlapping strokes, blade wiped on a towel between passes. Hard‑water area? Swap tap water for distilled or deionised. Sticky labels or tree sap yield to a plastic scraper and a dab of alcohol before your final polish. Avoid newspaper inks on modern coatings and skip paper towels that shed lint. For upstairs exteriors, fit a spray head to a long pole and finish with a squeegee, or use a hose rinse followed by your cornstarch cleaner for the last pass. The payoff is immediate—glass that disappears.
So there it is: the thrifty, science‑backed trick hiding in plain sight. A spoonful of cornflour (cornstarch), a splash of vinegar, and careful technique deliver windows that stay crisp, bright and truly streak‑free. It’s better for indoor air, kinder to budgets, and satisfying in a way only a perfect pane can be. Ready to retire pricey blue liquids and try the cupboard classic instead—what window, mirror, or glass surface will you transform first?
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