Koch-Chemie Glas Star "Gla" Glass Cleaner Concentrate 1000ml

Streak-free cleaning with Koch-Chemie Glas Star

What is Koch-Chemie Glas Star? A concentrated, alcohol-based glass cleaner that removes oil, grease, silicone, wax residues, and insect remains from windows, mirrors, and smooth surfaces without leaving streaks. Not suitable for matte finishes, wood, or untreated tint film edges.

Glass cleaner concentrate in its purest form is called "Glas Star" at Koch-Chemie — an alcohol-based professional glass cleaner from Unna, used neat or diluted up to 1:3 with distilled water. One liter of concentrate yields up to 4 liters of ready-to-use spray solution. The formulation has Daimler approval and has been standard in workshops and mobile detailing setups for years.

• Cost per application under 5 cents. With a 1:3 dilution, 1,000 ml of concentrate yield about 4 liters of spray solution. This is enough for approximately 130 vehicle window applications, each with 30 ml of spray volume. Even the 1,000 ml bottle thus costs less than one euro per complete interior cleaning.
• Alcohol-based also dries in winter. Water-based glass cleaners freeze in the spray bottle at -5 °C and leave streaks on the window. Glas Star evaporates residue-free even at low temperatures — at -10 °C, the wiping process still takes less than 30 seconds to be streak-free.
• Shine and glide additives without silicone oil residues. The concentrate contains glide aids that allow the microfiber cloth to slide easily over the window. Unlike silicone oil-containing "shine formulas," they leave no film that turns into smears during the next cleaning.

Practical tip from Detailing1: Dilute Glas Star exclusively with distilled water or osmosis water, never with tap water — the lime in the water would otherwise leave white drying marks despite the alcohol, which you'll see in the sun the next day. The practical mixture in our workshop is 60% concentrate to 40% distilled water for medium soiling. Only the official 1:3 is intended for pure re-cleaning.

Neat or diluted: the right mixture

Glas Star is mixed in a spray bottle with a Canyon CHS-3AN spray head — the concentrate bottle itself does not have a spray head, as it is intended for storage. For standard interior applications, mix 250 ml of concentrate with 750 ml of distilled water to make one liter of spray solution. This 1:3 mixture is the official manufacturer's specification and is sufficient for light to medium soiling.

For heavily soiled windows — nicotine films, baked-on insect residues on the inside of the windshield, old adhesive or sticker residues — use it neat. Spray directly onto the glass towel, not onto the window, to avoid drips on the dashboard or door panel. Neat is also the choice for the inside of the windshield, where outgassing from plastics forms a thin plastic film that diluted solutions only partially dissolve. You'll recognize this layer by the streaking effect in backlight despite a freshly cleaned window.

Common dilution error: concentrate first into the empty spray bottle, then water on top — this order leads to a foam crown that you'll be rinsing out for minutes. The other way is faster: first the water, then add the concentrate and swirl the bottle slowly, do not shake. This applies to any alcohol-based glass cleaner concentrate, not just Glas Star.

The ready-mixed spray solution has a shelf life of several months, as long as you store it frost-free and in the dark. Direct sun in a transparent spray bottle noticeably reduces the effect of the shine additives after about eight weeks. An HDPE bottle from the spray bottle set is therefore a more durable solution than any recycled clear bottle from the drugstore.

Always label the spray bottle with the mixing ratio and date. It may sound petty, but it saves frustration: if three months later the result suddenly gets worse, you'll immediately know whether it's due to the cloth, the mixing ratio, or an overaged solution. Clear labels or a permanent marker directly on the HDPE bottle are sufficient — the label will also survive accidental splashes with the alcohol-based concentrate itself.

Alcohol dissolves films. Not tint films.

The alcohol content reliably dissolves silicone, grease, wax residues, and light paint mist in one wipe — the main problem area for most interior windows. It also dissolves baked-on insects on the outside of the windshield if pre-soaked with water. This means Glas Star covers both interior and exterior cleaning, which is usually not the case with pure interior glass cleaners.

On the inside of the rear window, most glass cleaners perform worse because the embedded heating wires act as edges. Glas Star, thanks to the glide aid, moves smoothly over the wires and leaves no streaks there — provided you wipe in one direction with a glass-specific microfiber cloth, not in circles. A normal all-purpose microfiber cloth with a high GSM (over 400) does not push away the cleaning liquid, but absorbs it, leaving precisely the streaks you want to avoid.

Where Glas Star is not the right product: On the adhesive edges of retrofitted tint films, the high alcohol content can dissolve the adhesive over weeks. Here, dilute at least 1:3 and keep a distance from the edges. On anti-fog coated interior windows (some OEM windshields from 2020), neat Glas Star leaves streaks — test on a 5x5 cm area beforehand. It is unsuitable for matte surfaces, untreated wood, or acrylic glass (convertible rear windows); for these, the significantly milder Tugalin Glas-Teufel is available as a ready-to-use alternative.

The Daimler approval of the concentrate specifically means: The product has been approved in the manufacturer's material testing laboratory for use on the installed window materials and plastic frames of all current Mercedes models. Other manufacturer approvals are not official, but the material composition of German and European vehicle windows hardly differs — so the approval is a reliable indicator of general compatibility.

Concentrate for the workshop. Spray bottle for the car.

Anyone who maintains more than two vehicles is better off with glass cleaner concentrate than with any spray bottle solution: 10 liters yield 40 liters of spray solution, which, at a consumption of 30 ml per vehicle, corresponds to about 1,300 complete cleanings. Mobile detailers and workshops therefore almost exclusively opt for the 10 or 20-liter variant. Compared to ready-to-use 750 ml spray bottles, you save about 80% of packaging and 60% of costs for the same number of applications.

For private use, the 1-liter bottle usually lasts three to five years. If you mix once and then store the spray bottle frost-free in the garage, your interior cleanings for the next season are prepared. The variant with a spray head set is the beginner-friendly solution — concentrate plus a suitable HDPE spray bottle with a Canyon spray head in one order. This eliminates the hassle of separate procurement.

In the Detailing1 workflow, Glas Star follows the wheel and paint cleaning block, otherwise the spray mist of other cleaners will re-soil fresh windows. Inside, the windshield is cleaned last, after the cockpit and dashboard have been dusted with microfiber — otherwise dust particles will land on the still-wet window via the air current and you'll have to start over. Anyone who follows this sequence once will need half the time next time.

The most important insider tip for glass cleaner concentrate concerns the inside of the windshield: Keep the ventilation control on "off" or "recirculation." If fresh air is on, the fan draws dust from the engine compartment area to the window while you wipe — streaks are then inevitable.

Professional detailers also fold down the sun visors, because an astonishing amount of liquid collects there during spraying. When you're done and drive off, it runs down onto the freshly cleaned window as drops. Neither trick is in any data sheet, but they make the difference between "okay clean" and "delivered as from the workshop."

Anyone who regularly works with glass cleaner concentrate will develop their own system after a few months: a fixed spray bottle with a fixed mixture, a dedicated glass towel exclusively for windows (never for the cockpit or paint), and a second towel for drying. This separation prevents silicone oil residues from cockpit care products from transferring to the next window via the towel, leaving behind the notorious crescent-shaped streaks that are almost impossible to remove even with a second cleaning.

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.