I think the "techs" are using the word TARTAR because they heard an older tech use the term and they picked it up, not knowing what the term actually stood for...
I think what they are calling "tartar" is really "corrosion" - a white, powdery substance that results from 2 (or more) different metals being in close proximity and when subjected to skin perspiration or "salty water" - the metals act like two plates in a battery and start "trading" molecules back and forth...that shows up as "corrosion" or "tartar" - just taking your cellphone from a cool enviroment out into the hot, moist, sticky air of outdoors will cause condensation to appear on your gear...just like your glasses "fogging over" when you come out doors from a well air-conditioned building...just like your glasses, your cellphone will "fog up" and moisture will start blending into your electronic devices and eventually...the corrosion/tartar.
When you have the "glasses moment" - assume that your electronics is experiencing the same thing...then take the gear to a cleaner enviroment and if possible, remove the back covers, take out the battery and if possible, using a ShopVac with a blowing attachment on it, blow the gear out and let it dry...do what you can to keep the phone from getting "sweaty" or worse, wet at all...
Good luck!
