What grit sandpaper for wood?

Bare wood: the standard sequence

Start at 80 if the board is rough or has planer marks, at 120 if it is already dressed. Work up in single steps — 80, 120, 180, 220 — and stop. Four passes with a random orbital sander is usually enough for furniture; hand-sanding needs the same order and more time.

Stopping at 220 is not laziness. Finer grits burnish the surface: they compress the fibres rather than cut them, and the wood stops absorbing stain evenly. A blotchy stain is almost always a 320-grit problem, not a stain problem.

If you are painting rather than staining, stop earlier — 180 gives the paint something to key into. Smooth is not the goal on painted wood; grip is.

Between coats of finish

320 for a dry scuff, 400 if you are wet-sanding. The point is to flatten dust nibs and give the next coat a mechanical key, not to remove the coat you just applied. Two or three light passes with almost no pressure.

Wipe the surface with a damp cloth and let it dry before the next coat. That raises the grain slightly, so the finish sits flat instead of standing the fibres up.

Timber that behaves differently

Softwoods clog paper and need stearated (soapy) paper to stop the resin loading the grit. Hardwoods with interlocking grain — mahogany, sapele — tear out if you sand across the grain, so work with it and keep the pressure light. End grain always needs one grit finer than the face, because it absorbs finish three or four times faster and goes dark.

Plywood is the trap: sand it too hard and you cut through the veneer, which is often under a millimetre thick. 180 by hand is safer than 80 on a machine.

The wood grits, with microns

Technique matters as much as the number

Sand with the grain, always. A random orbital sander does most of the work but leaves swirl marks that only show under finish, so finish every session by hand, with the grain, in the direction the light will fall.

Use less pressure than feels productive. The weight of the machine is usually enough; pressing down clogs the paper, overheats the surface and rounds over edges you wanted crisp. Let the grit cut.

Change direction between grits — sand across the previous scratches for a few passes, then return to the grain. When the earlier scratch pattern disappears, that grit is finished. That is the only reliable way to know you have actually done the step rather than polished over it.

Clean between grits. Dust left on the surface gets dragged around by the next sheet and cuts scratches you did not intend. A brush and a tack cloth cost nothing and save the whole finish.

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