The innermost edge-seal material in many dual-seal insulating glass units, commonly serving as the principal moisture- and gas-vapor barrier between spacer and glass.
GlassRenu · Educational illustration
Meaning and boundaries
Primary does not mean structurally load-bearing; material and function vary with the specific IGU system.
Why it matters in glass restoration
Certain glazing materials, cleaners, solvents, blocks, or sealants may be incompatible with polyisobutylene or another primary seal.
Related terms
References
- National Glass Association — GANA Glazing Manual, 2022 edition
Publisher’s original source - ASTM International — C1369 — Secondary Edge Sealants for Structurally Glazed IGUs
Publisher’s original source - National Glass Association and FGIA — Compatibility Testing of IG PIB Primary Sealant with Respect to Glazing Materials
Publisher’s original source