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Secondary seal

Also called edge seal

The structural sealant that fills the channel around the edge of the unit.

The secondary seal fills the channel left between the panes outside the spacer. It is usually silicone, polysulfide or polyurethane. It bonds the two panes to the spacer so the unit acts as one piece, and it protects the primary seal from water and sunlight.

Edge of a double-glazed unit in section

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Insulating glass unit, edge in section

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