Sealant primers are matched to the sealant and substrate: some seal dusty, porous concrete and masonry, others chemically prepare metals, coatings or plastics. Membrane primers consolidate the surface and improve tack for self-adhered sheets. Primers have a set open window: applied too thick, left too long or allowed to get dusty, they become a weak layer instead of a bridge. Pull tests confirm the choice.
Primer on the precast faces only, don't slop it on the glass, and seal within the hour.
A primer that flashed off overnight and collected dust is usually worse than none; reprime anything left open longer than the data sheet allows.
Also heard as
- sealant primer
- membrane primer
Related terms
Two-rag wipe
Cleaning a joint face with a solvent-wet cloth followed immediately by a dry cloth, before the solvent evaporates.
Field adhesion test
A test that cuts a tab of cured sealant from an installed joint and pulls it to see whether it lets go of the substrate.
Adhesive failure
A sealant pulling cleanly away from one joint face, leaving the substrate bare.
Peel-and-stick
Field name for self-adhered membrane: rubberized asphalt or butyl sheet with a release liner on the back.