When 220 Is Not Fine Enough Before Water-Based Poly

Is 220 grit fine enough?

Usually, yes. Sanding bare wood to 220 grit is a suitable stopping point before many water-based polyurethane finishes. You may want a finer final pass when the wood is especially smooth or the finish will be viewed in strong light, but sanding finer is not automatically better. Very fine sanding can burnish some woods and affect how stain or other treatments absorb.

Follow the finish maker’s preparation directions first. If the label specifies a grit range, use it; recommendations can vary by product and by whether the wood is bare, stained, or already coated.

When to go finer than 220

Consider a light final pass with 320 grit if you can still feel slight roughness after sanding to 220, or if you are preparing a smooth, unstained surface for a clear finish. Use light pressure and keep the sanding even. On stained wood, test in an inconspicuous area before sanding further, since abrasion can lighten or remove stain.

Going finer is unlikely to solve deep scratches. If a scratch remains visible, return to the grit that removes it, then work through the intermediate grits in order and finish at the grit recommended for your coating. Skipping grits can leave scratch patterns that become more obvious under a clear finish.

Check the surface before applying poly

1. Inspect the wood in angled light. Look for scratches, uneven sanding, glue spots, and dents; clear finish can make these defects stand out.
2. Feel the surface with clean hands. A snag or rough patch may need attention, but avoid sanding through stain or veneer.
3. Remove sanding dust with a method approved by the finish manufacturer. Dust left behind can make the coat feel gritty.
4. Apply the finish according to its directions, including any guidance on stirring, application, and drying.

Water-based finishes can raise the grain, making the first coat feel rough even when the bare wood was sanded well. That does not necessarily mean the pre-finish sanding was too coarse. Let the coat dry as directed, then sand between coats only as the product instructions recommend. The between-coat grit may differ from the grit used on bare wood.

If the finish still looks scratched

Let the finish dry fully before deciding how to correct it. If scratches are in the bare wood beneath the coating, sanding only the topcoat more finely will not remove them; you may need to sand back to the wood and refinish. If the roughness is from raised grain or dust in the coat, a careful between-coat sanding may be enough. Avoid sanding through a thin coat, stain, or veneer. If you are unsure how much material can safely be removed, consult the finish manufacturer or a refinishing professional.