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What can't I use Universal Cleaner on?Updated a day ago

TL;DR: Universal Cleaner is safe for most household surfaces, but avoid raw soft metals (aluminium, copper, brass, zinc) and aftermarket window tints or specialty glass coatings like EnduroShield. These can discolour, etch, or peel when exposed to alkaline cleaners. When in doubt, spot test a hidden area first.


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Koh Universal Cleaner 20+ uses around the home
Koh Universal Cleaner safe for homes and surfaces

Why can't I use Universal Cleaner on soft metals?

Koh Universal Cleaner is alkaline at pH 12.5, which is strong enough to cut through grease but reactive with soft metals. Raw aluminium, copper, brass, and zinc can discolour, tarnish, oxidise, etch, or develop a cloudy film on contact. The reaction is chemical, not a cleaning product defect. Any alkaline cleaner will produce the same result with these metals. Sealed, lacquered, or coated versions of these metals are usually fine for cleaning but should be spot tested first to confirm the protective layer is intact.

⚠ Avoid raw soft metals

Raw aluminium oxidises or pits. Copper and brass tarnish or discolour. Zinc can develop a cloudy film. These are chemical reactions with any alkaline cleaner, not a Koh-specific issue. Sealed or coated versions of these metals are usually fine but spot test to be sure.

Raw aluminium Copper Brass Zinc

Can I use Universal Cleaner on window tints and glass coatings?

No. Avoid Koh Universal Cleaner on aftermarket window tint films (car windows, privacy films), protective window films, and specialty glass coatings like EnduroShield. These coatings can peel, cloud, lift at the edges, or strip when exposed to alkaline cleaners. Factory-installed automotive tints are usually more robust than aftermarket films but still worth checking with the manufacturer before using any alkaline cleaner. Always follow the manufacturer's cleaning guidelines for coated glass and treated surfaces.

⚠ Avoid on coated glass

Aftermarket window tints can peel or cloud. Protective window films can lift at the edges. Specialty coatings like EnduroShield can strip. Factory-installed automotive tints are usually more robust but still worth checking with the manufacturer before use.

Aftermarket tints Window films EnduroShield

What should I do if I'm not sure about a surface?

Spot test. There are too many specialty finishes, manufacturing coatings, and vintage materials in modern homes to list every incompatible surface. If a surface is unfamiliar, unusual, or valuable, spray a small amount of Koh Universal Cleaner on a hidden area, wait a few minutes, wipe with a microfibre cloth, and check for colour change, sheen change, etching, or texture change before committing to the full surface. Five minutes of testing beats a damaged surface. Spot testing is especially worth doing on natural stone, aged sealants, soft furnishings, and anything labelled as a specialty finish.

✓ Spot test when unsure

Pick a hidden corner, spray a small amount, wait a few minutes, wipe clean, and check for any change. Five minutes of testing beats a damaged surface. Especially worth doing on natural stone, aged sealants, soft furnishings, and anything marked as a specialty finish by the manufacturer.

Natural stone Sealed timber Specialty finishes Valuable materials
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Last reviewed: April 2026

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