How to Read Lead Glass Specifications for X-ray Windows

A lead glass window specification is short but dense: lead equivalence, thickness, transmittance, dimensions and tolerances. Misreading any of them produces either an over-priced window or a failed radiation survey.

Lead equivalence is the headline number - 1.5mmPb, 2.0mmPb, 3.0mmPb and so on. It states the pure lead thickness that would attenuate the same way. The required value comes from the room physics calculation, and the window must match the wall and door shielding - a 2.0mmPb wall with a 1.5mmPb window is a weak point at eye level.

Physical thickness is a different number. Lead glass reaches its equivalence at several times the equivalent in millimeters of actual glass; two suppliers with the same equivalence may quote different thicknesses. Compare equivalence, not thickness.

Transmittance describes optical clarity. Higher transmittance helps radiographers read monitors and observe patients through the window. Differences of a few percent are invisible; large differences suggest lower-grade glass.

Tolerances matter at installation. Windows ordered slightly oversize can be trimmed on site; undersize windows leak light and, in shielded walls, radiation at the edges. Specify plus-tolerance for width and height.

Edge quality and treatment are the durability story. Polished edges resist chipping; unpolished edges develop micro-cracks that grow with daily cleaning. For hospital use, insist on polished edges on all four sides.

Certification closes the loop. Reputable suppliers provide test reports tying the glass batch to its claimed equivalence - the document your physicist will ask for during the survey.

Order windows together with the doors of the same room from one supplier: matched equivalence, one set of documents, and no finger-pointing if a survey flags an overlap detail.