How do I sand and finish wood properly?

Working through the grits in order, sanding with the grain, and choosing between oil, wax and varnish.

Difficulty: intermediate
Time: 2 hr
Read: 3 min
Safety: caution

Short answer

Work through the grits in order without skipping — 80, then 120, then 180 — always along the grain. Skipping grits leaves scratches the next grade cannot remove, and they only appear once the finish goes on.

Sanding is a sequence, not a single action. Each grade removes the scratches left by the previous one. Skipping a grade means those scratches survive, invisible on bare wood and glaringly obvious under a finish.

Safety

Wear a dust mask when sanding — wood dust is a respiratory irritant and some hardwood dust is a recognised carcinogen. Paint in buildings from before the late 1970s may contain lead, which must not be sanded dry; get it tested first.

What you'll need

Sandpaper in several grades
Sanding block
Dust mask
Finish — oil, wax or varnish (optional)
Tack cloth (optional)

Step by step

Start with a grit appropriate to the surface.80 grit for rough or previously finished wood, 120 for reasonably smooth, 180 if it is already good. Starting too fine wastes a great deal of effort.
Always sand along the grain.Across the grain leaves scratches that show badly under any finish and are very hard to remove afterwards.
Work through the grits in order.80, 120, 180. Each removes the previous grade's scratches. Skipping from 80 to 180 leaves marks that appear when the finish goes on.
Use a block on flat surfaces.Fingers press unevenly and create hollows. A block keeps the surface flat, which matters most on tabletops and doors.
Remove all dust between grades and before finishing.Vacuum, then wipe with a slightly damp cloth or a tack cloth. Dust left on the surface is sealed under the finish permanently.
Choose the finish for the use.Oil for a natural look that is easy to repair. Wax for a soft sheen but little protection. Varnish or lacquer for hard-wearing surfaces like floors and worktops.
Apply thin coats and sand lightly between them.Several thin coats are far better than one thick one. A light rub with fine paper between coats gives a much smoother result.
Raise the grain before the first coat with a water-based finish.Wipe with a damp cloth, let it dry, and sand lightly. It lifts the fibres so the first coat does not leave the surface rough.

Tips

Oil finishes are the easiest to repair — a worn patch can be re-oiled invisibly. Varnish must usually be stripped and redone.
Test any finish on an offcut or a hidden area. Wood colour changes considerably under oil and it is not reversible.
An orbital sander saves a great deal of time on large flat areas, but finish the final grade by hand along the grain.

Common mistakes

Skipping grades of sandpaper — Each grade removes the previous one's scratches. Skipping leaves marks that are invisible until the finish goes on.
Sanding across the grain — It leaves scratches that show clearly under any finish and are difficult to sand out afterwards.
Not removing dust before finishing — It is sealed permanently under the finish, giving a gritty surface that has to be sanded back and redone.

Questions people ask

What order should I use sandpaper grits in?

Coarse to fine without skipping: typically 80, then 120, then 180. Each grade removes the scratches left by the previous one, and skipping leaves marks that show under the finish.

Should I use oil, wax or varnish on wood?

Oil for a natural look that is easy to repair, wax for a soft sheen with little protection, varnish or lacquer for hard-wearing surfaces such as floors and worktops.