Short answer: TR90 resists the sudden, high-stress damage — drops, sitting on the frame, temple over-bending — that cracks acetate and permanently deforms metal, but it's still vulnerable to prolonged heat exposure, harsh chemical cleaners, and UV degradation over many years, none of which are obvious risks to most wearers. Understanding the difference between what TR90 survives and what it doesn't helps set the right customer expectations.
The scenarios TR90 was specifically engineered for are exactly the ones acetate and metal handle worst: being sat on, stepped on, or having a temple arm bent well past its normal range. TR90's molecular structure gives it real elastic memory in these situations — it flexes and returns rather than cracking (acetate's typical failure mode) or staying bent out of shape (metal's typical failure mode). This is the entire basis for its reputation as the "unbreakable" frame material, and for typical accidental impact and stress scenarios, that reputation is well earned.
Acetate tends to fail suddenly under stress but ages gracefully otherwise, developing a patina some wearers even like. Metal deforms gradually under repeated handling (loosening at the hinges, slight bends from being taken on and off) but rarely fails catastrophically. TR90 sits between them: it survives sudden stress better than either, but its flex-and-recover property does very gradually reduce over years of repeated bending, meaning a 5-year-old TR90 frame won't spring back quite as crisply as a new one — a normal aging pattern, not a defect.
Clean with mild soap and water rather than alcohol-based lens sprays applied directly to the frame (as opposed to the lens itself), avoid leaving the frame in a hot car or direct sun for extended periods, and don't rely on TR90's flexibility as an excuse for rough handling — it recovers from occasional stress remarkably well, but repeated extreme bending still shortens its working life over time.
TR90's durability story is genuinely strong and a real selling point — but overselling it as literally indestructible sets customers up for disappointment if a frame does eventually show wear. Framing it accurately (exceptional resistance to accidental damage, normal gradual aging like any material) builds more durable customer trust than an "unbreakable" claim that a five-year-old frame will eventually contradict.
Browse Salvador Eyewear's 202-model TR90 frame range.