Scope:

ASTM D7786 test method may be used by paint companies and raw material suppliers to assess the interactions of primers and topcoats with respect to their ability to provide good enamel holdout.

Test Procedure:

In ASTM D7786 test method, a substrate is coated with a test primer and allowed to dry (primed topcoat). A non-porous substrate is coated using a standard topcoat (unprimed topcoat). The difference in the gloss reading is the indication of the enamel holdout.

Video 01: ASTM D7786 Enamel holdout

Specimen size:

Wet film thickness of approximately 0.075mm should be used.

Data:

In ASTM D7786 testing, the enamel holdout data is provided in terms of Enamel Holdout % retained
Enamel Holdout (% difference) = 100*(Gʋ – Gₚ)/G 

Enamel Holdout (difference) = Gʋ – Gₚ

where, Gₚ = gloss of primed topcoat, Gʋ = gloss of unprimed topcoat