A dedicated primer is formulated specifically to seal, bond, and create a uniform surface: PVA seals new drywall, shellac-based primer blocks stains, adhesion primer bonds to glossy existing paint. Paint-and-primer products are finish paints with slightly higher solids content. On new drywall, they do not replace a proper PVA primer — the paper face and joint compound absorb paint at different rates and will flash without a dedicated sealer underneath. RainFire Builders uses dedicated primers on all new construction surfaces. Paint-and-primer products are appropriate only when repainting already-primed and painted walls in good condition.