Natural mica has extremely high heat resistance; transparency ; optical clarity ; flexibility ; flatness and is unbreakable. The transparency of mica is not affected by the repeated fluctuations in heating and cooling and is not attcked by most of the gases and vapours it might come into contact with. In addition, mica resists shocks, strains and vibrations and therefore can easily be used in place of glass where there is a likelyhood of exposure to radiant heat, breakage or cracking. As steam boilers are frequently shut-down and started up again, this places extreme demands on the transparent glasses fitted between CAF sealing gaskets and cushion joints of the level gauges. It is therefore essential to protect these glasses with Mica Shields by fitting them on the side facing the medium chamber. Mica Shields are a must where saturated steam pressure exceed 350 psi (up to 5689 psi) and working temperatures exceed 196 deg. C (up to 600 deg. C).

Mica Shields also protect the inner surfaces of the transparent glasses against erosion from chemical abrasion and from corrosive chemical effects of alkaline solutions, boiler waters, caustics, hydrofluoric acids, hot concentrated phosphoric acids, sodium and potassium hydroxides and other contaminated viscous or corrosive media. It provides an excellent sealing strength against acids, sodium, water, air and oil at extreme pressures and temperatures and completely eliminates the risk of cracks, breakage, jerks, shocks, combustion effects, etc. In fact, Mica Shields serve effectively in closing the spy holes of observation doors of level gauges and columns.