Do I need to sand after using Zinsser primer?

Whether you need to sand after using Zinsser primer depends on which Zinsser primer you used, the surface, and desired finish smoothness, but generally light sanding improves adhesion and smoothness for topcoat, though not always required. For Zinsser Bulls Eye 1-2-3 water-based primer, which is all-purpose for drywall, wood, and previously painted surfaces, sanding after priming is not strictly required for adhesion, as it sticks well to glossy surfaces without sanding, but light sanding with 220 grit sandpaper after it dries removes raised grain, drips, and creates smoother base for topcoat, especially for cabinets and trim where smooth finish matters. For Zinsser Cover Stain oil-based primer, light sanding is recommended after drying to knock down texture and improve topcoat adhesion. For Zinsser BIN shellac-based primer, which dries very fast and can leave slight texture or ridges, light sanding with 220 grit after 45 minutes is often recommended to smooth surface before topcoat, as shellac dries hard and sanding improves smoothness. If primer is on drywall that will be painted with flat paint, sanding may not be needed beyond knocking off bumps. If painting cabinets, furniture, or glossy surfaces, sanding after primer helps topcoat bond and look professional. Always wipe dust after sanding with tack cloth. Do not sand heavily to break through primer. So answer is not mandatory but light sanding is beneficial for best results.