Grit Beats Brand Every Time

Walk into any timber merchant or DIY shed and you'll find sandpaper in every colour, price and packet size imaginable. It's tempting to assume the expensive stuff will give you a better finish. In reality, the biggest factor in how your wood turns out is the order in which you use your abrasive grades, not the name printed on the backing. A cheap sheet of 120 grit followed properly by 180 and 240 will beat a premium sheet used at random every single time.

Get the sequence right and you'll spend less time sanding, use fewer sheets, and end up with a surface that takes stain, oil or paint evenly. Get it wrong and you'll either leave scratches you can't see until the finish goes on, or polish the surface so smooth that the next coat has nothing to grip.

What the Numbers Actually Mean

Grit numbers tell you how many abrasive particles pass through a sieve per square inch during manufacture. The higher the number, the finer the paper. So 60 grit is coarse and aggressive; 400 grit is fine and produces a near-polished surface.

• 40–60 grit: Heavy removal. Stripping old paint, flattening rough sawn timber, shaping edges. Use with care, as these leave deep scratches.
• 80–100 grit: The first proper pass on planed timber or after a coarse cut. Good for removing marks and levelling joints.
• 120–150 grit: The workhorse grade. Prepares most surfaces for finishing and removes the scratches left by 80.
• 180–220 grit: Fine prep. Ideal before applying stain, oil or a first coat of varnish. This is where wood starts to feel genuinely smooth.
• 240–320 grit: Between coats of finish, or the final rub-down before wax. Not for bare timber.
• 400 grit and above: Specialist work — polishing finishes, preparing a surface for French polish, or getting a glass-smooth feel on turned items.

A handy rule when you're unsure: never jump more than roughly double the grit. Going from 80 straight to 240 leaves scratches that are hard to shift later, because the fine paper just polishes the tops of the gouges rather than cutting them out.

The Sequence That Works for Most Projects

For a typical piece of furniture or joinery, a three-stage sequence handles almost everything: 120, then 180, then 240 if you're finishing with a film finish such as varnish or polyurethane. If the timber is rough, or you're working with reclaimed boards, start at 80.

The important part is to sand in one direction along the grain, not in circles. Circular scratches are almost impossible to see on bare wood under indoor light, but the moment you wipe on a stain they appear like rings on a pond. Work methodically along the length of the board, overlapping your passes, and let the weight of the sander do the work rather than pressing down.

Don't skip a grade because the wood already feels smooth. Feel can deceive. Running through each grade properly takes minutes and saves you an hour of regret.

Remove Dust Between Every Stage

This is the step most people skip, and it's the one that ruins finishes. Dust from a coarser grit contains hard particles that, if left on the surface, get dragged around by the next sheet and gouge fine scratches into your work.

Between each grade, do the following:

• Vacuum the surface with a brush attachment, or blow it off with compressed air if you have it.
• Wipe over with a tack cloth, or a cloth very slightly dampened with white spirit.
• Tap out or brush down your workpiece, and clean the bench so fresh dust doesn't land back on it.
• Change or clean your sanding sheet, as a clogged sheet rubs rather than cuts.

When you've finished the final grade, wipe down again and look at the surface at a low angle under a bright light. Any remaining scratch marks will show up as dull lines. If you see them, drop back a grade, sand them out, and work forward again.

Matching Paper to the Task

Different jobs call for different abrasives, and choosing the right type saves both your time and your finish.

• Aluminium oxide: The default for wood. Durable, affordable, and works with hand sanding and power sanders alike.
• Silicon carbide: Sharper and better for wet sanding between finish coats, and for metals.
• Garnet: A natural abrasive that breaks down as it cuts, giving a lovely finish on bare timber. Pricier, but kind to softwoods.
• Zirconia and ceramic: Tough stuff for heavy stock removal with belt sanders. Overkill for hand work.

For sanding between coats of varnish or lacquer, go for a very fine silicon carbide paper — 320 or 400 — used dry and very lightly. You're only knocking back the nibs and dust specks, not cutting into the coat itself. Wipe the residue off before the next coat goes on.

Small Habits That Save Big Trouble

A few practical points to keep in mind. Change your paper as soon as it stops cutting efficiently, because a worn sheet burnishes the wood and can glaze the surface so that stain won't take. If you're using a random orbital sander, keep it moving; dwelling in one spot creates dip marks that become visible the moment light hits the finished piece. On edges and corners, sand by hand with a block, because power sanders round them over far too easily.

Finally, test your surface before you commit to a finish. Wipe a small area with a damp cloth — this raises the grain and shows you exactly what the wood will look like with the first coat on. It's the cheapest quality check you can do, and it'll tell you whether you need one more pass with a finer grade before you start applying anything at all.