Resources
How Anti-Fog Mirrors Work — Heating Pad, Coating, or Neither
There are two different technologies sold under the same name, and they behave differently when the room is very humid.
Short answer: most anti-fog bathroom mirrors use a heating pad bonded to the back of the glass. It warms the mirror slightly so its surface stays above the dew point and water vapour does not condense on it. A smaller group uses a hydrophilic coating, which does not stop condensation but spreads it into a thin film you can see through. They are different technologies with different behaviour.
Why mirrors fog in the first place
Fog is condensation. Warm, humid air meets a surface that is cooler than the air's dew point, and the vapour turns into droplets on it. Those droplets scatter light, which is why the reflection disappears.
The mirror is not doing anything wrong — it is simply the coldest large surface in the room. That framing points at both solutions: either stop the surface being the coldest thing, or stop the water forming droplets.
The two approaches
| Heating pad (demister) | Hydrophilic coating | |
|---|---|---|
| What it does | Warms the glass above dew point | Spreads water into a thin film |
| Does condensation still form? | Largely prevented | Yes, but it does not scatter light |
| Needs power? | Yes | No |
| Warm-up time | Needs a few minutes before it clears | Immediate |
| Wears out? | Pad has a service life | Coating wears with cleaning |
The heating pad is the common build in commercial and hotel work, because it keeps a clear zone reliably and it can be wired to come on with the lights. The coating approach appears more often on lower-cost consumer units.
What a demister pad does not do
It does not dry the room, and it does not heat the whole mirror unless the pad covers the whole panel. Most pads cover a zone — typically the area a person actually uses — so a large mirror can be clear in the middle and fogged at the edges. That is expected behaviour, not a fault, and it is worth setting the expectation with a client who has specified a full-height mirror.
It also needs a supply. In a bathroom that means the electrical work follows local regulation for the zone the mirror sits in, and the supply position has to be planned with the mirror position rather than after it.
Where ventilation matters more than the mirror
If a room fogs badly and stays fogged, the room is the problem. Extract that runs for long enough after a shower does more for the mirror than any pad. Specifying a demister into a room with no working extract treats the symptom.
For commercial washrooms with high turnover, the practical combination is adequate extract plus a demister zone at the used height — not a heated full-height panel, which costs more and solves less than people expect.
Our builds
The front-lit LED bathroom mirror with 3-CCT dimming and anti-fog and the round backlit LED bathroom mirror with anti-fog both use a bonded demister pad, wired with the mirror's supply.
Send the room conditions — extract, mirror size, and whether power is available at the mirror position — and we will confirm the build. The range sits in bathroom mirrors; we come back within 24 hours.