Wood finishing

A finish does three things, and which of them you care about decides everything else. It protects the wood from moisture, spills and wear. It changes the appearance, almost always by deepening colour and raising figure. And it alters the surface you touch, from bare and dry through to glass. No finish is best at all three, and most of the craft is choosing which to prioritise for a particular object.

The second organising idea is where the finish sits. A penetrating finish — oils, and oil-heavy blends — soaks into the fibres and cures there, leaving little or nothing on top. A film finish — varnish, lacquer, shellac — cures as a layer sitting on the surface. That distinction predicts almost everything practical about a finish: how it feels, how it fails, and above all how it is repaired. A penetrating finish is repaired by wiping more on. A film finish is repaired by dealing with the film, which is a considerably bigger job.

The part beginners consistently get wrong is the ratio of effort. Finishing is roughly three-quarters preparation and one-quarter application, and every defect in the surface is amplified rather than hidden by whatever goes on it. A finish is not a coat of paint; it is closer to a magnifying glass.

The actual work

Surface preparation

The dividing line

Penetrating or film-forming

Easiest to repair

Oil and wax

The real hazard

Rags, not vapour

1. 1

   Step 1: Buy hardwax oil, abrasives and a metal bin with a lid

   One litre of hardwax oil or Danish oil, a pack of abrasives from 120 through 320, a handful of lint-free cloths, and the bin — which is a safety item and is on this list before anything else because of it. Under £60 and enough for several pieces.

   You will know it worked when: You have a complete kit and somewhere safe to put the rags.

2. 2

   Step 2: Make offcuts of the same wood your real piece is

   Every judgement in finishing is species-specific, and a test piece in pine tells you almost nothing about oak. Prepare three or four offcuts exactly as you would the real thing.

   You will know it worked when: You have test pieces that will behave like the job.

3. 3

   Step 3: Sand through the grits, then raise the grain

   120, 180, 240, 320, none skipped, sanding with the grain. Then wipe with a damp cloth, let it dry, and go over it lightly again with the final grit to remove the fibres that stood up.

   You will know it worked when: The surface stays smooth after it has been wetted once.

4. 4

   Step 4: Inspect in raking light before you open the tin

   A lamp low and nearly parallel to the surface. Everything you find now is a five-minute fix; everything you miss is a strip-back.

   You will know it worked when: You have found and dealt with marks you could not see from above.

5. 5

   Step 5: Apply thin, wipe off the excess, and wait properly

   Wipe it on, give it a few minutes, and take off everything that has not soaked in. Excess left to cure on the surface is the classic beginner result — sticky, patchy, and worse than no finish at all. Then leave it alone for as long as the tin says rather than as long as you would like.

   You will know it worked when: A dry, even surface with no tacky patches.

6. 6

   Step 6: Deal with the rags before you leave the workshop

   Spread them out flat in the open to dry, or soak them in water. Never folded, never in a pile, never in a plastic bin. Do this on the first piece so it becomes what you do rather than what you remember to do.

   You will know it worked when: Nothing in the workshop is generating heat while you are asleep.

• Drying oils — linseed, tung, and the blends — Soak in and cure within the fibres, leaving a low sheen and a surface that still feels like wood. Very forgiving to apply — wipe on, wipe off — and trivially repairable, because a worn patch is fixed by wiping more oil on it. The trade-off is real: modest protection against water and none worth the name against heat or solvents, and a slow cure. This is the family the rag warning is about.
• Hardwax oils — Oil-and-wax blends that behave like an oil to apply and leave rather more protection than one. They have become the default for furniture and floors in the last twenty years for good reason: most of the repairability of oil with a usable fraction of the durability of a film. Still a drying oil as far as the rag bin is concerned.
• Waxes — Sit on the surface, add sheen and a particular tactile quality, and protect very little. Best understood as a topcoat over something else rather than a finish in its own right, and easily the most reversible thing you can put on wood — which is exactly why conservation work favours it.
• Shellac — A resin dissolved in alcohol, brushed or padded on, drying in minutes and building a film in layers. Extraordinarily quick to work with, beautiful under other finishes as a sealer, and forgiving because each new coat partly dissolves the last — so witness lines do not form. Weak against water, alcohol and heat, which is why it is a poor choice for a kitchen table and a superb one under something else. Applied as a padded high build, it becomes French polishing, which is its own craft.
• Varnishes and polyurethanes — Cure into a genuinely tough film and are what you use where the surface has to survive drinks, heat and children. Slow to dry and therefore vulnerable to dust settling into the wet film, unforgiving of brush marks, and awkward to repair — a damaged film usually has to be dealt with as a film rather than patched. Available in oil-based and water-based versions that behave quite differently.
• Water-based systems — Once dismissed and now genuinely good. Far lower solvent exposure, very fast drying, and they do not add the amber warmth that oil-based finishes do — which is a drawback on oak and an advantage on maple or a pale piece you want to stay pale. The lower hazard makes them the sensible default for anybody finishing indoors in a space they live in.
• Abrasives, which are the actual consumable — A finish is only as good as the surface under it, and abrasives are where most beginners under-spend and over-economise. Worn paper burnishes rather than cuts, which leaves a surface that looks smooth and takes finish unevenly. Fresh paper, and the full sequence of grits without skipping, is not fussiness — skipping a grit leaves scratches the next one is too fine to remove.

The single most useful idea in finishing is that a finish reveals rather than conceals. Raising figure and deepening colour is exactly the same optical effect that makes a missed scratch obvious, so anything you can see on bare wood you will see more of afterwards, and several things you cannot see on bare wood will appear.

The standard sequence is to work through abrasive grits in order without skipping — each grit exists to remove the scratches of the one before it, so a jump leaves marks the finer paper cannot reach. Where to stop depends on the finish: penetrating oils generally want a less-polished surface than a film finish, because a burnished surface accepts less oil, and going finer than necessary can leave an oil finish looking patchy.

Two habits separate people whose finishes look right from people whose finishes look nearly right. The first is raising the grain: wiping the sanded surface with a damp cloth, letting it dry, and knocking back the fibres that stand up, before the finish does the same thing permanently. This matters most with water-based finishes. The second is inspecting in raking light — a lamp low and almost parallel to the surface, which throws shadows from defects that overhead light hides entirely. Running a clean hand over the surface with your eyes shut finds the rest.

On application, the pattern that holds across nearly every finish is that thin coats beat thick ones, more of them, with the surface dealt with between. Thick coats sag, trap solvent, cure slowly and fail as a layer. The temptation to build it in one go is where most amateur film finishes go wrong.

Progression in finishing is not towards harder products. It is towards controlling more variables, and the order below is roughly the order in which each one stops being somebody else’s problem and starts being yours.

1. 1

   Step 1: Get a repeatable oil finish on something that matters

   The same hardwax oil or Danish oil on three pieces, with the same preparation sequence and the same number of coats, until the result stops varying. Almost nobody does this and it is where the craft actually starts.

   You will know it worked when: A finish you can predict rather than one you hope for.

2. 2

   Step 2: Learn to see the surface rather than the finish

   Raking light and a clean hand with your eyes shut. Once you can find the scratch before the finish does, preparation stops being a chore you rush and starts being the thing you are actually good at.

   You will know it worked when: You find defects before the oil finds them for you.

3. 3

   Step 3: Add shellac, and use it as a sealer

   Cheap, fast, forgiving, and the most useful second product in the craft. It dries in minutes, each coat partly dissolves the last so witness lines do not form, and it sits beautifully under other things.

   You will know it worked when: A second material, and a much shorter feedback loop.

4. 4

   Step 4: Take on a film finish, on something that has to survive

   A varnish or a water-based system on a surface that will meet drinks and heat. This is where dust, brush marks and cure schedules become real, and where the discipline of thin coats stops being advice.

   You will know it worked when: A durable surface, and a healthy respect for dust.

5. 5

   Step 5: Learn to repair rather than to refinish

   The step most people skip. Knowing which damage is a wipe of oil, which is a local repair and which genuinely means dealing with the whole film is what separates somebody who finishes furniture from somebody who strips it.

   You will know it worked when: You fix a mark rather than starting again.

6. 6

   Step 6: Only then think about spraying

   A step change of £200–£800 plus somewhere to use it, and a genuinely different set of ventilation requirements. It is optional — most furniture in the world was finished by hand — and it is the wrong first answer to a finish that is not going well.

   You will know it worked when: A considered decision rather than an equipment purchase.

The rest of it, in the order it actually bites:

• Dust, not fumes, for most people — Sanding is where the real exposure is in a hobby workshop, and hardwood dust is the part worth taking seriously rather than the smell of the oil. Extraction at the tool beats a mask, and both beat neither.
• Read the product, not the category — "Danish oil" and "teak oil" are marketing names rather than defined formulations, and two tins with the same name can have quite different contents. The safety data sheet is the document that tells you what you actually have.
• Skin — Repeated solvent contact defats skin and is a slow, cumulative problem rather than a dramatic one. Nitrile gloves are cheap; the ones in the kitchen drawer are not the right polymer for solvents.
• Storage — Solvents and their vapour do not belong next to a boiler, a pilot light or anything that sparks, and part-used tins of drying oil skin over and are worth decanting rather than leaving half full.
• Food and skin contact claims — This page makes none. Whether a cured finish is suitable for a chopping board or a child's toy is a question for the manufacturer's own statement about that specific product, and general craft lore about it is unusually unreliable.