-A mica shield is a barrier that protects glass from direct attack by alkaline boiler water, dissolved solids, and high-velocity steam, and high temperature caustic which would otherwise etch, pit, or cloud the bare glass
-Used only with transparent style gage glass, on the wetted side
-A mica shield is a thin sheet placed in front of the gage glass
-Level gages that include mica shields must be maintained on a regular basis