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Mistless Mirror

 Mirror that automatically demists itself, and uses no power
 
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I like to shave in the shower (you should try it!) so I have a little mirror in there. It mists up, but I've found that warming it up under the hot water keeps the condensation off. Of course, the same thing can't be done with the big mirror in the bathroom, so I got to wondering how the mirror might do it itself.

Simply coating the back of the mirror with a chemical with the following properties, should do the trick.

The chemical is anhydrous. When it reacts with the humidity in the air, from someone taking a shower or a bath, it heats up, keeping the condensation off the mirror. When the air dries out again, the chemical looses it's water, and takes heat out of the mirror.

The process repeats when someone has another shower.

—rocketmagnet, Nov 13 2002

(?) Deluxe 3x Fog-Free Shower Mirror http://www.sharperi...iew.jhtml?sku=SE390
'Only' $99.95 USD. No power required. [phoenix, Oct 04 2004]

(?) Rain-X Anti Fog http://www.rainx.co...les/auto_glass.html
Baked. You put it on the FRONT of the mirror, however. [krelnik, Oct 04 2004]

(?) And baked again http://www.brooksto...search_words=mirror
[mrthingy, Oct 04 2004]

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       Nice idea. Trouble is if the powder reacts chemically with water, it's got to unreact chemically as well, not just dry out. You'll have new compounds in there, along the magnesium oxide lines.
—General Washington, Nov 13 2002
   

       Smear the mirror with a thin film of soap. (Shaving soap works excellently, should you happen to be a user of such.)
—angel, Nov 13 2002
   

       Welcome to the bakery.   

       I think this idea is baked, the form of Rain-X Anti Fog (see link). Although they advertise it as an automotive product, it works quite well on bathroom mirrors. Unlike the description in the idea, this substance goes on the front of the mirror, like angel's thin film of soap.
—krelnik, Nov 13 2002
   

       Hmmm. I think that the General has it about right - while there are a number of compunds that release heat when transforming from their anhydrous to their hydrated form, they won't just "dry out" - a substantial rise in temperature - not just dehumidified air - is needed to reverse the process. Silica gel is like this.   

       I can't think of any easlily-reversible physical/chemical system that will do whet you want, although the overall idea has merit.   

       How about passing the hot water for the shower through the back of the mirror ? It should stay hot enough for long enough to allow you to shave.
—8th of 7, Nov 13 2002
   

       //membership card//
Heck, I don't even have one
—thumbwax, Nov 14 2002
   

       I think that, like 8/7 does, passing the hot water plumbing through a matrix of pipes that run behind the mirror, mounted in the wall, would provide ample defogging capabilities. Sharper Image pretty much owns this space, though.
—bristolz, Nov 14 2002
   

       The simple solution is to hinge the top of the mirror so that before the shower you can lift it and face the reflective mirror surface towards the ceiling. As long as it's not too close to the ceiling or the room completely fills with steam it'll stay clear.
—lostbedouin, Dec 18 2008
   

       I've been in hotels where some kind of defogging device is built into the bathroom mirrors - I'm guessing it's some kind of heating element (either electrical, or just using the heat from the hot-water plumbing - though I seem to remember experimenting with switching off the lights (and presumably the mirror's heating element) and seeing fogging) you can even achieve this by raising the overall ambient temperature of your bathroom prior to showering - as long as the mirror is as warm as the water-vapour, it shouldn't collect condensation.   

       Another thing you could try is having some large metal object (some sort of wrought-metal scuplture might be nice) through which is plumbed cold water that would act as a defoggeriser by attracting as much air-bound water to itself as it can, pulling it from the atmosphere and so leaving less free to cling to your mirrored surfaces.
—zen_tom, Dec 18 2008
   


 

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