The first cloth, dampened with the solvent the sealant maker specifies, dissolves oils and dirt; the second, clean and dry, lifts them off while still in solution. Letting solvent dry on the surface just redeposits the contamination. It is the standard cleaning step for glass, metal and coated surfaces before priming or sealing, especially in structural glazing.
Two-rag wipe on every mullion, and turn the rag to a clean face each pass or you're just moving dirt around.
Also heard as
- two-cloth wipe
- two-cloth method
Related terms
Primer
A thin liquid brushed or wiped onto a joint face or deck so the sealant or membrane bonds reliably.
Adhesive failure
A sealant pulling cleanly away from one joint face, leaving the substrate bare.
SSG
Structural silicone glazing, where glass is held to its frame by silicone instead of exterior caps or stops.
Laitance
A weak, powdery skin of cement and fines on the surface of concrete that sealants and membranes cannot hold onto.