Acer Liquid Z6 - Manual (Page 60)

60 - Warnings and precautions
4. DO NOT expose your phone to extreme temperatures. For example,
do not leave your phone on the dashboard of a car on a hot day or
when temperatures are below freezing point. Also, keep it away
from heaters and other sources of heat.
5. DO NOT use or store your phone in any location that is dusty, damp
or wet.
6. DO use a soft, damp cloth to clean your phone. If the surface of the
screen becomes soiled, clean it with a soft cloth moistened with
diluted window-cleaning solution.
7. DO NOT press down on the screen with force, otherwise you may
crack the screen.