My mirrors are going black and blotchy around the edges — can they be fixed or must they be replaced?
Several of our mirrors (bathroom especially) have gone black, cloudy or blotchy around the edges and in spots. I gather this is the silvering backing degrading.
- Can "de-silvered" mirrors be repaired/re-silvered, or do they need replacing?
- What causes it — moisture, cheap mirrors, cleaning products?
- How do I stop new mirrors doing the same?
Trying to understand if it's fixable. What's the deal with mirrors going black?
3 answers
Short answer: those black/cloudy edges are DE-SILVERING — the reflective backing (silver + protective layers) on the back of the mirror is corroding, usually because MOISTURE has got in at the edges (bathrooms are the classic), often helped along by harsh cleaners running to the edges or a cheaper mirror with a thinner backing. In practice, de-silvered mirrors are almost always REPLACED rather than repaired — professional re-silvering exists but for most household mirrors it's not economic versus a new mirror, and you can't "clean" de-silvering off (it's damage to the back coating, not dirt on the surface). Prevent it on the new one with a good-quality (thick-backed) mirror, sealed edges, decent bathroom ventilation, and by not letting cleaner pool at the edges.
What's happening: - De-silvering: the mirror's reflective backing (the silvered layer and its protective paint) is corroding/oxidising, which shows as black, grey or cloudy edges and spots. It starts at the edges because that's where moisture reaches the backing. - It's damage to the back coating, not surface dirt — so no amount of cleaning the front fixes it.
Why it happens: - Moisture at the edges — steamy bathrooms are the number-one cause; water/vapour creeps behind the edge and attacks the silvering. - Harsh/ammonia cleaners running to and sitting at the edges can degrade the backing (spray the cloth, not the mirror, and keep cleaner off the edges). - Cheaper mirrors with thinner/lower-grade backing de-silver faster; edge damage during fitting gives moisture a way in.
Fix or replace: - Replace is the normal answer — re-silvering is a specialist process that's rarely economic for standard household mirrors, so once it's de-silvered, a new mirror is usually the practical fix. - (Framing/tricks can hide a little edge blackening cosmetically, but the corrosion continues underneath.)
Prevent it on the new one: - Good-quality mirror (thicker, better-protected backing — moisture-resistant/"bathroom grade"). - Sealed edges and careful fitting (no edge damage). - Ventilate the bathroom (extractor) to cut steam dwell time. - Clean smart: spray the cloth not the glass, and keep cleaner away from the edges.
Common mistake: scrubbing harder at "stains" that are actually de-silvering (they won't come off), or replacing with another cheap mirror in the same steamy, unventilated spot. Replace with a quality mirror, seal/ventilate, and clean gently — a glass and mirror specialist can supply/fit the right one. Anyone's bathroom mirror last much longer once ventilated properly?
Learned this replacing a blotchy bathroom mirror — it wasn't dirt, it was the backing gone, and no cleaning touches it. The new one we bought as a proper bathroom-grade mirror and made sure the edges were sealed and the extractor actually runs, and it's held up far better. The spray-the-cloth-not-the-glass tip matters too; ammonia cleaner wicking to the edges is a known killer. Cheap mirror + steamy unventilated bathroom = black edges within a couple of years. Spend a bit more on the mirror and sort the ventilation and it lasts.
Good to know re-silvering isn't really worth it for normal mirrors — I'd wondered if there was a repair, but replacing with a better one and fixing the cause is clearly the move. The edges-first pattern makes sense now; that's where the moisture gets to the backing. Bathrooms are brutal on mirrors here with the steam. We'll seal the edges and keep cleaner off them on the replacements, and make sure the fan's doing its job. Annoying that a "stain" turned out to be permanent damage, but at least the fix and prevention are clear.
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