The material in MDC glass viewports is Corning type 7056 glass, the most commonly used vacuum window material in the industry. MDC glass viewports provide high and ultrahigh vacuum compatibility for basic optical applications. 

Glass viewports are available on MDC’s standard vacuum mounts including Del- Seal™ CF, Kwik-Flange™ and Large-Flange™ ISO flanges with clear apertures from 5/8 to 5-3/8 inch diameters. 

Since glass is susceptible to scratching and weak under point stresses, caution must be exercised when heating or cooling glass viewport assemblies. Thermal gradients in excess of 10°C per minute must be avoided. Because of implosion hazard, glass viewports with scratches or nicks should be replaced. 

For customers desiring a viewport with a replaceable glass substrate, MDC offers a weldable 4 inch view diameter Pyrex® viewport assembly. These viewports are constructed with Corning type 7740 glass and are sealed in place using an elastomer gasket and suitable for service to 1x10^-8 Torr.