Analyzing the iPhone's moisture sensor Every time I'm near a Genius Bar I see a lot of ENT (ear, nose, throat) microscopes peering down the headphone jack of various iPhones. I asked about it and found that the moisture sensor is down there, and if your device got wet then it turns red, and the purpose of that is that you don't have a warranty and don't get a free new device if it has mysteriously died but the cause is moisture.

I'm curious about how these things work and whether this simple examination could be subverted. I don't have a wet iPhone and I'm not looking to defraud Apple here, but I'm curious.


The sensor must involve a chemical reaction, if it didn't show the indicator color when it dried it wouldn't be much good. What is the reaction and is it reversible? Would the required reagent be safe to drip down the headphone opening?
Could one buy a new sensor component, open the phone and replace it?
How about simply getting a material that looks like the sensor, opening the phone and putting it in place of the sensor - an inert sensor?
Simplest of all, painting the sensor - if the "OK" color is white then a paint marker should do.


Again, not trying to get a free phone here. I'm curious about devices like this since I saw my first "tip-n-tell" on a shipping carton, and played with Maxim iButton temperature loggers.
An inert "sensor" would be white paper.
An actually working sensor could be paper coated with cobalt(II) chloride, whose hexa hydrate (cobalt chloride "containing" water) turns light red.
If you want to tamper with the original sensor, think of water free clear coat.