• Improves the sealant’s adhesion in many situations.
  • Many sealants perform well without the use of primers.
  • Priming is not a substitute for good joint design and sealant application.
  • Laboratory and/or field adhesion testing is required for verification of whether a primer is necessary for proper sealant adhesion.
  • Primers should always be used for horizontal and submerged joint applications.
  • Care must be taken to apply primer only to the surface to be sealed.  Most primers stain and are difficult or impossible to remove.
  • Almost all sealants, to achieve adequate adhesion for moving joints, require cement based substrates to be primed.
  • Primers must be installed properly (e.g. use the correct primer, do not apply to thick or to thin, and requires drying or curing time before sealant application).
  • Whenever possible prime substrates before insertion of the sealant backing.

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