2.
Braze material may be noticeable on the glass around the sealing area of quartz viewports. This is not a manufacturing defect, products are verified such that braze material creep does not occlude the specified view area and the product passes leak check requirements. This material is not removed so as not to risk damaging the viewport lens.
3.
For safety, we strongly recommend that no viewport is exposed to a temperature ramp of greater than 2-3°C per minute, and that no viewport be exposed to direct thermal radiation. To limit thermal gradients when heating viewports, we recommend the viewing area and the flange be covered with many layers of aluminum foil to act as a reflective shield.