Koch-Chemie Glas Star "Gla" Glass Cleaner Concentrate 10l

Streak-free glass with Koch-Chemie Glas Star

What is Koch-Chemie Glas Star? An alcohol-based glass cleaner concentrate that pulls oil, grease, silicone, wax residue, and squashed bugs off windows, mirrors, and smooth surfaces without streaks. Keep it off matte paint, bare wood, and the edges of aftermarket tint film.

Glass cleaner concentrate in its purest form goes by "Glas Star" at Koch-Chemie — an alcohol-based pro cleaner from Unna that you use neat or cut up to 1:3 with distilled water. One liter of concentrate makes up to four liters of ready-to-use spray. The formula carries a Daimler approval and has been a workshop standard and mobile-detailer go-to for years.

• Under 5 cents per application. At 1:3 dilution, 1,000 ml of concentrate makes about four liters of spray — roughly 130 vehicle-window applications at 30 ml per spray. The 1,000 ml bottle works out to less than a euro per full interior glass clean.
• Alcohol base dries down in winter. Water-based cleaners freeze in the bottle at -5 °C and pull streaks across the panel. Glas Star flashes off residue-free at low temperatures — at -10 °C you are still streak-free in under 30 seconds.
• Shine and glide without silicone-oil residue. The concentrate carries glide aids that let the microfibre run easily across the glass. Unlike silicone-oil "shine formulas," they don't leave a film that smears the next time you clean.

Detailing1's tip from the bay: Cut Glas Star only with distilled or osmosis water, never tap water — the lime in tap water leaves white drying marks the alcohol can't override, and you'll spot them in tomorrow's sunlight. Our day-to-day mix sits at 60% concentrate to 40% distilled water for medium soiling. The official 1:3 is for clean refresh passes, not for the heavy stuff.

Neat or diluted: dial in the mix

You mix Glas Star into a spray bottle with a Canyon CHS-3AN spray head — the concentrate bottle itself ships without a spray head because it's a refill format. For standard interior work, 250 ml of concentrate into 750 ml of distilled water gives you a liter of spray. That 1:3 ratio is Koch-Chemie's official spec and handles light to medium soiling without drama.

On heavily-soiled glass — nicotine film, baked-on bugs on the inside of the windshield, old adhesive or sticker residue — you go neat. Spray straight onto the glass towel, not the panel, so you don't fling drops onto the dashboard or door card. Neat is also the move for the inside of the windshield, where outgassed plastics build a paper-thin film that diluted mix only half-dissolves. You spot that layer by the streaky glare in backlight even after you've just cleaned.

Dilution mistake we see often: concentrate first into the empty bottle, then water — that order builds a foam crown you'll be rinsing for minutes. Reverse it: water first, then drop the concentrate in and swirl slowly, don't shake. Holds for any alcohol-based glass cleaner concentrate, not just Glas Star.

Pre-mixed spray lasts several months as long as you keep it frost-free and out of direct light. Sun in a clear spray bottle eats the shine additives noticeably after about eight weeks. An HDPE bottle from the spray-bottle set holds up far better than any recycled clear bottle out of the drugstore aisle.

Label every bottle with the ratio and the date. Sounds petty, saves frustration: if three months down the line the result gets worse, you know straight away whether it's the towel, the ratio, or an aged mix. A clear label or a permanent marker straight on the HDPE works — the writing survives the odd splash of concentrate.

Alcohol cuts films. Not tint film.

The alcohol content pulls silicone, grease, wax residue, and light overspray in one wipe — the bread-and-butter of most interior glass work. It also cuts baked-on bugs on the outside of the windshield if you pre-soak with water first. So Glas Star handles both inside and outside glass — most interior-only cleaners can't say the same.

On the inside of the rear screen, most cleaners struggle because the embedded heating elements act like edges. Glas Star runs smoothly over the wires thanks to the glide aid and won't streak there — as long as you wipe in one direction with a glass-specific microfibre, not in circles. A normal all-purpose microfibre with a high GSM (over 400) doesn't push the liquid across, it soaks it up — and leaves you the streaks you were trying to avoid.

Where Glas Star isn't the right call: along the adhesive edges of aftermarket tint film, the high alcohol content can lift the glue over weeks. Cut to at least 1:3 and keep clear of the edges. On anti-fog coated interior glass (some OEM windshields from 2020 onward), neat Glas Star can streak — patch-test on a 5×5 cm spot first. For matte surfaces, bare wood, or acrylic (convertible rear windows) it's out — for those the much milder Tugalin Glas-Teufel sits in the range as a ready-to-use option.

The Daimler approval on the concentrate means this: the product has been signed off in the manufacturer's materials lab for use on the glass and plastic trims fitted to all current Mercedes models. Other manufacturer approvals aren't officially documented, but the material composition of German and European vehicle glass barely varies — so the Daimler tick is a reliable proxy for broader compatibility.

Concentrate for the shop. Spray bottle for the car.

If you maintain more than two vehicles, the glass cleaner concentrate beats any pre-mixed spray solution: 10 liters make 40 liters of spray, which at 30 ml per car works out to around 1,300 full cleans. Mobile detailers and shops almost always grab the 10 or 20-liter variant. Versus ready-to-use 750 ml spray bottles, you save around 80% in packaging and 60% in cost for the same number of applications.

For private use, the 1-liter bottle usually rides three to five years. Mix once, store the spray bottle frost-free in the garage, and your interior cleans for the next season are queued up. The variant with the spray-head set is the easy-entry option — concentrate plus a matching HDPE spray bottle with a Canyon spray head in one order, no separate sourcing needed.

In the Detailing1 workflow, Glas Star follows the wheel and paint cleaning block, otherwise the overspray from other cleaners lands back on the freshly cleaned glass. Inside, the windshield gets done last — after cockpit and dash have been dusted with microfibre — otherwise loose particles ride the air current and you're starting over. Get the order right once, half the time on the next car.

The most important insider tip for any glass cleaner concentrate hits the inside of the windshield: kill the fan or run on recirculation. With fresh air on, the blower pulls dust out of the engine bay onto the glass while you're wiping — streaks are basically guaranteed.

Pros also flip the sun visors down, because an astonishing amount of spray ends up on them. When you're done and drive off, it runs back onto the freshly cleaned screen as drops. Neither trick lives in any data sheet, but they're the difference between "okay clean" and "looks like a fresh hand-over."

If you work with the concentrate regularly, after a few months you build your own system: one dedicated spray bottle at one fixed ratio, a glass-only towel that never touches cockpit or paint, and a second towel for the dry-off. That separation stops silicone-oil residue from cockpit care creeping over the towel onto the next window, where it leaves the half-moon streaks that even a second clean barely takes off.

Application of Koch-Chemie Glas Star

Dilute, spray, wipe in one direction

Dilute Glas Star exclusively with distilled water or osmosis water — never with tap water. The official mixture is 1:3 (250 ml concentrate to 750 ml water). In the Detailing1 workshop, for medium soiling, we work with 60:40 (60% concentrate, 40% water), because the drying time is shorter and the result is more robust.

The order of mixing is crucial: First, put the water into the HDPE spray bottle, then add the concentrate. The other way around will create a head of foam that takes minutes to settle. Swirl the bottle slowly, do not shake it, otherwise the foam will remain.

Spray generously on the pane — about 5 to 8 sprays per square meter. Immediately wipe with a glass-specific microfiber cloth in one direction, not in circles. For heavily soiled interior windows (nicotine, plastic outgassing), work neat and apply the concentrate directly to the cloth.

Clean the inside of the windshield with the ventilation on "off" or "recirculation," otherwise the fresh air mode will draw dust onto the damp pane. Fold down the sun visors beforehand — when spraying, liquid collects there which will later drip back onto the pane. Wipe the inside of the rear window along the heating elements in the direction of the wires.

Notes: Maintain distance from tinting film adhesive edges — the alcohol content can dissolve the film adhesive over weeks. On anti-fog coated OEM windshields from 2020 onwards, first test on a 5×5 cm test area. Not for matte surfaces, untreated wood, or acrylic glass (convertible rear windows) — for these, the milder Tugalin Glas-Teufel is available in the product range as a ready-to-use alternative. Store concentrate frost-free between 5 and 30 °C, in the dark and in the original bottle. Mixed spray solution has a shelf life of several months; write the date and mixing ratio on the bottle.