Discoloration of Glass Panel Sealants

This paper investigates the cause of discoloration that has appeared along the interior glazing system in a State of Ohio public university building. The discoloration is evident in both the head and sill details and is evident adjacent to the glass pane in the glazing sealant as well as at the locations where the frame meets the adjacent concrete structure. These discoloration spots are located throughout the interior of the building, e.g. glass wall of the lecture hall, glass stair railing, windows, etc. By reviewing the architecture details, the top of the glass panels (1/2" or 13/16" thick) is anchored to a flush mounted aluminum frame and wood blocking supports the bottom and laterally anchored by two rolls in shims in a milled aluminum channel. The shims both on the top and bottom are sealed by a silicone caulk. The performance failure of discoloration may be caused by the corrosion of the shims due to the poor durability of materials, a reaction between the shims and the caulk, or poor craftsmanship of panel installation. The paper identifies the cause of the discoloration and discusses the potential economic loss. Through the investigation, the discoloration is surmised to be caused by a plasticizer leached out from a rubber shim. No performance data was provided for the rubber shim in the drawings or specifications. Additionally, this paper reconstructs the design, specification, and submittal process and identifies how and where the mistake was made, who should have known. The paper concludes with lessons learned from the failure of architects, engineers, and construction professionals to avoid similar failures in other projects.