Eyeglasses and cleaning cloth Breathing on glasses and wiping them with a shirt sleeve gets treated as a harmless shortcut, and rinsing them under hot tap water feels like the more thorough clean. Both habits cause real, permanent damage — and the hot water problem in particular isn't just chemical. It's a physical mismatch between two layers of the lens that expand at different speeds. The Twist: Heat Cracks the Coating Through Expansion, Not Just Chemistry Anti-reflective (AR) coatings are made of ultra-thin inorganic metal oxide layers sitting on top of a polycarbonate or high-index plastic lens. Hot water heats both layers, but the plastic lens expands considerably faster than the harder metal oxide coating can keep pace with. That mismatch forces the coating to crack into microscopic spiderweb lines — a condition called crazing. It's structural damage, not a chemical reaction, and once it happens it can't be polished or cleaned away. The same thing happens without ...
Scientific approaches to daily living, home maintenance, and food safety. Delivering evidence-based tips and EHS-compliant life ideas by Jenny