Finishes on timber joinery: lacquer, oil, hardwax, stain and paint

At a glance

AWS is the Architectural Woodwork Standards, 1st edition (2009, US): its ratings are subjective judgements for generic products. The Wood Handbook is the US Forest Products Laboratory's (2021). Hardwax oil is not in either; it is described from trade usage. Stain is a colour step under a film or oil, and is not in the basic systems. No pass levels are given. The partner workshop's finish data and your sample govern.

Film or penetrating: the first choice

The first choice is whether the finish sits on the timber or soaks into it. The US Forest Products Laboratory puts it plainly. A film-forming finish, such as varnish or lacquer, gives a smooth surface that is generally easier to clean, better at keeping the wood from getting dirty and more resistant to staining than a penetrating finish such as an oil, which leaves the surface texture as it was. A thicker film also protects against scratches and dents, but a film wears away with repeated cleaning and abrasion, and the handbook says thicker, harder films are needed for high wear. Oils give a more natural look and are the easier to refinish. The drawing shows the difference in section.

Three cautions come from the same chapter. First, the names are not reliable: the handbook says the nomenclature around clear finishes and stains is confusing because manufacturers do not follow a standard set of definitions, so ask for the system and its performance, not a trade name. Second, gloss and clear finishes accentuate flaws, planer marks, raised grain and, above all, joints, because two pieces of timber change thickness differently with humidity. Third, wood changes colour as it ages indoors, dark wood getting lighter and light wood darker, so panelling should stay free of pictures for the first two to three months to avoid shadows (Wood Handbook, ch. 16, Finishing Interior Wood).

The families compared

The Architectural Woodwork Standards (2009, US) describe 13 finish systems and rate them one to five (5 excellent, 1 poor) for general performance. They call the ratings subjective judgements of generic products, and say that differences of 10 points or fewer on their overall scores are not generally significant enough to justify the added expense of a higher-rated system. The table gives nine of the systems that correspond to the families above and seven of the characteristics:

Read it for the pattern, not the points. The catalysed systems and conversion varnish rate highest for heat, stain and moisture, and the oil lowest for them but easiest to repair. Nitrocellulose lacquer and the water-based acrylic yellow most. The standards also say catalysed polyurethane is difficult to repair, ultraviolet-cured finishes are difficult to repair on site and need a handheld lamp, and that nitrocellulose, pre- and post-catalysed lacquer and catalysed polyester affect the flame spread of the wood. Intermixing systems is likely to cause problems (1.2.13.2). Four things the table cannot tell you: it is generic, it is from 2009, water-based and ultraviolet technology has moved since, and hardwax oil is not in it.

Two other points from the standards are worth carrying into a specification. A system is specified by its number and name together with any colour or grain enhancement, because stains, washes and fillers are not part of the basic systems (1.2.13.6 and 1.2.13.7). And factory finishing is usually specified for high-quality work, for its consistency, control of film thickness and curing in a controlled atmosphere, while jobsite finishing is better avoided (1.2.12 and 1.3.5). Where a grain is open, such as ash or oak, a filler is needed for a smooth film; closed-grain woods such as maple and cherry usually are not (1.2.10).

Tests: what each one assesses and what it cannot tell you

A finish is proved by testing a panel, not by naming a system. For furniture surfaces five European standards are the reference, and FIRA, the furniture research and testing body, named them in a 2018 article together with a technical report of precision data for all five (PD CEN/TR 17292:2018):

Three things matter when you ask for a result. First, ask for the edition: two of these standards were revised in 2023 and 2024, and the reports a finisher holds may cite an older edition. Second, ask for a test on a panel of the same substrate finished identically to the work: the scratch standard itself allows testing on test panels of the same material finished in an identical manner, on unused surfaces. Third, set the rating you need. We have not seen a published pass level for any of these tests and give none: a bar top, a bedside table and a wall panel need different results, and the partner finisher can say what a given system achieves. The AWS scores above rest on different tests (ASTM D1308 for chemicals, D4060 for wear, D1211 for cold check and D3359 for adhesion), so they are not interchangeable with the European ratings.

Sheen: write a number

Sheen is how shiny a surface is, and it is independent of colour. The usual measure is gloss units read with a glossmeter at a set angle, 60 degrees for most finishes on furniture and joinery (the standard for it is ISO 2813; we name it and did not read it). The words matt, satin, semi-gloss and gloss are not defined by any standard we read, so write a number. Our own lacquer pages give working bands of about 10 (dead matt), 30 to 40 (satin) and up to about 90 (mirror gloss), described there as a percentage of reflected light; those bands have not yet been checked by measurement, so treat them as a starting point.

Choose sheen with the surface in mind. The Wood Handbook warns that high gloss needs more attention to the surface because it accentuates imperfections, especially joints; our lacquer guide says the same colour reads differently at each sheen and that colour and sheen should be approved together, on a sample, under the project's own lighting. The Architectural Woodwork Standards make the control sample the reference for finishing done on site, with the finisher responsible for meeting or exceeding it for colour, texture and sheen; the same principle suits workshop finishing.

Samples, faces, touch-up and care

The standards read are consistent about what a specification should include.

• Samples first. The Architectural Woodwork Standards ask for samples to be submitted and approved before any finishing. A range of colour is to be expected within one species, so a minimum of three samples are submitted, each at least 305 mm square on a panel product (Section 5, 4.1.2). That is a US rule; the principle travels.
• All faces. Panel products need balanced coats for stability (1.2.5), and concealed surfaces next to exterior concrete walls should be back-primed (1.3.1.2). See timber movement in panelling and veneer and MDF decoded.
• Moisture. The finisher is to report in writing any moisture content above 12% in the product or in the surrounding wall surfaces (4.1.1.3).
• Touch-up. Jobsite touch-up after delivery or installation is a typical exclusion (2.3.3). Say who does it, and what is supplied.
• Fire and chemicals. Specify fire resistance and chemical resistance where they matter (1.3.7), and prefer fire-rated substrates to fire-retardant finishes where the codes allow (1.2.4). See the fire documentation matrix.

Care. The standards say modern finishes need no polishing, oiling or waxing, except true oil-rubbed surfaces, and that polishing oils, cleaning waxes and silicone products can impede later touch-up (Section 2, 1.2.2). They advise a soft, lint-free cloth lightly dampened with water, no abrasives or ammonia cleaners, wiping moisture off at once, and avoiding hot pans and direct sunlight (1.3.3 to 1.3.6). Put these in the handover notes.

Questions to ask by use. A bar top or restaurant table meets spilled liquids, hot cups and abrasion, so ask for cold-liquid, wet-heat, dry-heat, abrasion and scratch results. A bedside table meets heat and liquids. A wall panel meets little wear but shows joints and sheen. A bathroom or spa surface meets moisture and steam, so read the moisture rows and the sealing of every face. A sunlit surface meets colour change. Our lacquered furniture guide, lacquer page and French polishing guide cover how the partner workshops approach each.

Finish: [two-pack catalysed lacquer], [open pore / closed pore], sprayed in the workshop on [substrate], [ ] coats over [sealer], every face and edge finished with the same system. Sheen [ ] +/- [ ] gloss units at 60 degrees, measured on the approved control sample. Colour or stain reference [ ]. System named by type and performance, not trade name.

Before production the finisher is to supply a report from [an accredited test house] on a panel of the same substrate finished identically (same system, coats, sheen and cure), showing results for surface resistance to cold liquids (BS EN 12720), wet heat (BS EN 12721), dry heat (BS EN 12722), abrasion (BS EN 15185) and scratching (BS EN 15186, method [A / B]), current editions stated, to achieve [rating] for [ ].

[Three] control samples, each not less than [305] mm square on panel products, showing the colour range, grain and sheen, signed and dated, one held by [ ]. Production to match them. Touch-up kit [ ] supplied; jobsite touch-up by [ ].

Care notes issued at handover: a soft, lint-free cloth lightly dampened with water; no abrasives, ammonia cleaners, wax or silicone polish; spills wiped at once; mats under hot items; protect from direct sunlight [where relevant].

Standards and sources

• BS EN 12720, 12721, 12722 (2009+A1:2013): surface resistance to cold liquids, wet heat, dry heat: BSI listing for 12721 read (current, under review). Not read: confirm editions; ISO 4211 series may supersede.
• BS EN 15185:2023 (abrasion) and BS EN 15186:2024 (scratching): 15186 listing read; 15185 edition from search. Not read.
• PD CEN/TR 17292:2018 and FIRA news article (13 Dec 2018): Article read (archived Dec 2019). Report not read.
• USDA Forest Products Laboratory, Wood Handbook (2021), chapter 16: Read 5 Nov 2026.
• Architectural Woodwork Standards, 1st edition (2009), Sections 2 and 5: US standard. Read 5 Nov 2026.

Questions we are asked

Lacquer or hardwax oil on a table top?

They trade different things. The US Forest Products Laboratory says a film finish such as lacquer is generally easier to clean and more resistant to staining than an oil, which leaves the texture of the wood and is easier to refinish. For a table that will take spills, hot cups and daily wear, ask the finisher for results on a panel for the cold-liquid, wet-heat, dry-heat, abrasion and scratch tests, and set the rating you need. Hardwax oil is not covered by the sources we read, so ask for its own test data.

What does BS EN 12720 test?

Surface resistance to cold liquids, on rigid furniture surfaces. It belongs to a set with BS EN 12721 (wet heat), BS EN 12722 (dry heat), BS EN 15185 (abrasion) and BS EN 15186 (scratching). We have not read the standards, so we cannot give the liquids, durations or rating scale: ask the test house, and check the edition cited in any report.

Is there a pass mark for these tests?

We have not seen a published pass level for the five furniture surface standards, and give none. The result is reported as a rating, and the level you need depends on the use: a bar top is not a wall panel. Do not copy a rating from another project; ask the partner finisher what the system achieves on a panel and set the requirement from that and from the use.

What sheen should I specify?

Write a number rather than a word: gloss units at 60 degrees on the approved sample. Matt, satin and gloss are not fixed by any standard we read. Our lacquer pages give working bands of about 10, 30 to 40 and up to 90, to be confirmed by measurement. Gloss shows every flaw and joint, so it needs the flattest base.

Can a finished surface be repaired on site?

It depends on the system. The Architectural Woodwork Standards say nitrocellulose lacquer and oil are the most repairable, catalysed polyurethane and ultraviolet-cured finishes difficult. Mirror gloss shows a local repair in the reflection, so a whole door or panel may be re-sprayed. Say who does touch-up in the specification, and supply a kit.

Does a finish affect the fire class of the board?

It can. The Architectural Woodwork Standards say nitrocellulose, pre- and post-catalysed lacquer and catalysed polyester affect the flame spread of the wood, and recommend fire-rated substrates in place of fire-retardant finishes where codes allow. Ask for a classification that covers the board and the finish together, and see our fire documentation matrix.