MDF Adhesion Problems
Cause
Paraffin wax is often used in the manufacture of MDF to improve the water resistant properties.
Some of the wax treatment can remain on the surface and can affect the adhesion of primer coating when applied without any form of preparation.
Lightly sand down and wipe over with Methylated Sprit and allow to dry.
Check that the selected paint manufactures priming coat is suitable and if necessary apply to a prepared to check the adhesion.