Laminated glass

In Cardinal Glass Industries' glossary, laminated glass is a type of safety glass made of two or more layers of glass with one or more plastic interlayers sandwiched between them, the plastic usually polyvinyl butyral, or PVB. Where that plastic can be reached from outside the pane is the detail a cleaner works from.

The National Glass Association (NGA) supplies that detail in its Glass Technical Paper FB01-00: “The plastic interlayer in laminated glass is generally exposed around the periphery of the window glass; cleaning fluids and their vapors must be kept away from this area.” The sentence names a place, the periphery rather than the face of the pane, and it names vapors along with fluids, so the concern reaches past liquid that touches the edge.

The same paper sets the chemistry. For “laminated glass, or windows and doors containing laminated glass,” NGA's instruction is to use nothing corrosive, “such as solvents, acids, bases or other chemicals,” and its examples of materials that “may cause harm” open with “Bleach (or other solutions containing sodium hypochlorite),” the compound defined under sodium hypochlorite.

Two neighboring terms are easy to mistake for this one. Heat treatment is a separate property, the one behind tempered glass. Nor is the interlayer the edge seal of an insulating glass unit, which Cardinal describes as “two or more panes of glass separated by a spacer and sealed around the edges”; when that seal gives way, the result is seal failure.

The glass makers draw the line from laminated glass to impact windows themselves. PGT, describing how its WinGuard hurricane windows work, writes: “Our hurricane windows and doors are made with laminated glass, which is composed of two pieces of glass bonded together by a strong interlayer.” Cardinal Glass Industries calls its Sea-Storm product “impact-rated laminated glass.”

Each maker is describing its own product line. No document read for this entry says that every impact window is laminated, so treating an impact window as laminated glass is reasoning from those makers' lines, and whether a particular window contains it is for that window's maker to confirm. What makes a window impact rated at all is a separate definition, given under impact window.

Laminated glass matters on a roof job because of chemistry. The Asphalt Roofing Manufacturers Association's bulletin on algae discoloration says the stain may be lightened with “a solution of liquid household bleach (sodium hypochlorite) and water,” and bleach and other sodium hypochlorite solutions head NGA's list for laminated glass. Keeping a bleach roof solution and its vapors off impact glass is therefore a technical requirement of the trade wherever a roof wash and impact glass share a house, and solution carried past its target has a word of its own, overspray.

The rest of an impact window's care has answers of its own: whether impact windows can be cleaned like regular windows follows the published glass routine pane by pane, and what the sealants and gaskets around a pane do and do not stop is answered under whether window cleaning can hurt the window seals.