finish
Sanding and Simple Finishes
Sanding is where projects go to look homemade or handmade — and the finish decides which. The grit sequence that actually matters, dust control between coats, and four forgiving finishes explained honestly: what each protects against, and how long each really takes to cure.
Grit progression · four finishes, plainly · cure times · Mostly waiting on cure times
SANDING Sanding: the grit ladder
Sandpaper grits are a ladder — each rung removes the scratches of the one before. Skip a rung and the scratch survives under the finish, where it shows up forever.
- Start where the surface is80 grit is only for shaping and removing mill marks or glue scars. Sound, surfaced lumber usually starts at 120.
- Climb one rung at a time80 → 120 → 180 → 220 for film finishes; oil finishes can stop at 180–220 too. Never jump more than one step — roughly, never more than half again the grit number.
- Clean between gritsVacuum and wipe with a tack cloth or a barely damp rag at every change. A few loose 80-grit grains under a 180 disc keep cutting 80-grit scratches all day.
- Finish by hand, with the grainAfter the last machine pass, a few strokes by hand with the final grit, in the grain’s direction, erase the sander’s swirl pattern. Using a water-based finish? Raise the grain first — wipe with water, let it dry, then take the final pass.
| Grit | Job |
|---|---|
| 80 | Shaping, heavy mill marks, old-finish removal |
| 120 | First pass on sound lumber; levels glue lines |
| 180 | The working finish grit; last grit under paint |
| 220 | Final pass before oil or film finishes |
| 320 | Between coats only: knocks down dust nibs |
FINISHES Four finishes, explained plainly
| Finish | What it is | Protection | Cure |
|---|---|---|---|
| Boiled linseed oil | An oil that soaks in and hardens in the wood. Wipe on, let sit, wipe off. | Low — looks and feel, not armour. Water rings happen. | Dry in 24–72 hours; full cure up to a week. |
| Hardwax oil | Oil plus wax in one or two thin coats. The modern beginner favourite. | Moderate — resists spills that are wiped up; repairs invisibly with a spot recoat. | Handle in hours; full cure about 7 days. |
| Wiping varnish | Polyurethane thinned about 50/50 with mineral spirits; wiped on like an oil, builds like a varnish. | High — real film protection for tabletops and benches. | Recoat in 4–6 hours; usable in days; full cure ~30 days. |
| Brush-on polyurethane | Full-strength film finish, brushed on. | Highest of the four — the armour finish. | Recoat per can (2–6 hours); full cure up to 30 days; shows dust and brush marks the most. |
- Thin coats, more of themThree thin coats beat one thick one every time: thick finish stays soft, traps runs, and can peel. Wiping varnish is thin by design — 3–6 coats is normal, and each takes minutes.
- De-nib between coatsEvery coat traps a few dust nibs. Between coats, a light pass with 320 grit — or a crumpled brown paper bag — knocks them flat. Wipe clean, then recoat.
- Respect the cure, not the dry“Dry to touch” is hours; “cured” can be a month for oil-based films. A tabletop used hard in week one wears a finish that would have survived easily in week five.
Stop and think
Oily rags can catch fire by themselves. Rags soaked in linseed oil or hardwax oil generate heat as the oil cures, and a balled-up rag in a garbage can is a genuine fire starter — this is the most serious hazard in this guide. Lay used rags flat, outdoors, on concrete until they’re stiff and dry, or drop them into a metal can filled with water. Never leave them wadded in a pile. And sand with a mask on: finish sanding makes the finest dust in the shop, and sanders stir it exactly where you breathe.
WATCH OUT Common beginner mistakes
- Skipping grits to save time80 straight to 220 leaves 80-grit scratches that the finish magnifies. The ladder is the shortcut; there isn’t a faster one.
- Sanding through veneerPlywood faces are a whisper thick. On plywood, start at 150–180, sand gently, and never park a spinning sander in one spot.
- Finishing in a cold garageBelow about 15 °C, varnishes level poorly and oils cure slowly or not at all. Finish indoors, or wait for a warm spell — the winter guide has the full rules.
- Judging the finish wetWet finish looks darker and glossier than it will cured. Judge a test board, fully dried, in the light the piece will live in.
Good to know
Raking light tells the truth. Before the final coat, hold a lamp low across the surface: every scratch, nib, and glue fingerprint leaps out at a shallow angle and hides under ceiling light. Five minutes with a work light is the difference between a finish you’re proud of and one you explain.