This is an ongoing debate with the drywall industry. What is a true level 5, skim coat joint compound, drywall primer that equalizes porosity or a proprietary product?
I was under the impression the intent of a level 5 was to eliminate joint banding or photographing through a gloss paint when subjected to critical side light. I also thought joint banding was caused from a porosity difference from face paper to joint compound. Drywall primer will equalize the porosity, but not stop joint banding?
Now I am told it is the texture between the face paper and the joint compound causes the joint banding and not the porosity. This seems odd and contradictory. I should see the difference in texture looking face on at the wall. The porosity makes sense, since the sheen is what alters and only at an angle.
ASTM is looking at altering levels of finish, particularly level 5 and the skim. What do the guys that actually do the work think? What do you use for a level 5. And why does no industry define what a drywall primer is? Who should apply drywall primer? The drywaller? The painter?