Sealant Adhesion: Don't Forget to Clean

woman caulking

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How best to get a firm seal on your substrate? The Ins and Outs of Caulking states that nothing adheres well to a dirty surface. In addition, new and apparently clean metal components may have oils in their surfaces left from manufacturing processes. Likewise, the extrusions of vinyl, vinyl-clad wood, and wood–plastic composite windows may have residual extrusion die lubricants on their surfaces.

Satisfactory sealant adhesion requires removal of such contaminants. Wiping with a clean rag moistened with mineral spirits is an effective method of removing surface oils and die lubricants. This can, however, pose health and fire risks if done carelessly, and residual mineral spirits that do not fully evaporate before caulk is applied may compromise adhesion. Substituting denatured alcohol for mineral spirits generally poses fewer health risks, and alcohol’s relatively rapid evaporation rate is more likely to leave a clean dry surface. Organic solvents, while generally effective at removing organic surface contaminants such as oils, may not be compatible with all substrates; this is an additional reason that justifies caution in their use. Surfaces contaminated with dirt, airborne dust, and mud usually are most effectively cleaned with a well-rinsed water-wetted rag. Rinsing the rag in a detergent solution can aid in surface cleaning, but if this is done, residual detergent left on surfaces will interfere with caulk adhesion.

If you decide that using detergent solution is necessary to obtain adequate surface cleaning, you must follow the cleaning with a thorough rinsing with a water-wetted rag. It can be difficult to ascertain if the rinsing was adequate; therefore try water and a non-abrasive nylon cleaning pad before resorting to use of detergent solution. Because porous surfaces are generally absorptive and thus difficult to adequately rinse, use of detergent solution on them as in preparation for caulking is not recommended. At application, surfaces must also be free of ice or frost. At below-freezing temperatures, frost may accumulate on surfaces from an applicator’s breath; this is among the reasons that manufacturers commonly restrict application temperature.