Lacquer sheen levels and spray finish specification

At a glance

Bands, coats and repair notes are what our own lacquer pages say; no standard defines the words. Gloss figures are working bands, not tolerances.

Sheen is a number

Sheen is how much light a surface reflects as a mirror would, and it is separate from colour. Our lacquer page gives the working range as a dead matt of about 10, a satin of 30 to 40, and a mirror gloss of about 90, and says the same colour reads differently at each step, so colour and sheen are sampled together. Those figures are the studio's own working bands from its pages. The words matt, satin, semi-gloss and gloss are not defined by any standard we read, so a specification should carry a number, a measuring angle and a unit, not a word.

The unit is the gloss unit (GU), read on a glossmeter. Our live pages describe sheen as a percentage of reflected light. A specification should say GU and the angle, because a percentage with no method is not a measurement.

Measuring it: gloss units and ISO 2813

BS EN ISO 2813:2014 is the standard for measuring the gloss of coatings. The BSI listing gives its title as Paints and varnishes. Determination of gloss value at 20 degrees, 60 degrees and 85 degrees, dated 31 October 2014 and current. It specifies a method at the three angles (geometries), for non-textured coatings on plane, opaque substrates; for other specimens the values are comparative and may not match what the eye sees. The 2000 edition was withdrawn on 31 October 2014. We read the BSI listings and not the standard, so the clause on which angle to use for which gloss range is not quoted here; ask the workshop which angle it reads at, and state it.

A second standard, BS EN 13722:2004 Furniture. Assessment of the surface gloss, appears on standards-shop listings as published on 20 September 2004 and current. We saw only its title. If a furniture-specific method matters to your project, ask your testing laboratory or the standards body to confirm its scope against ISO 2813 before you cite it.

What to write. A gloss figure, a tolerance, the geometry, the unit, and where it is read. No tolerance for a decorative lacquer was found in anything we read, so the tolerance is for the workshop to propose and you to approve on a sample. Measure on a flat area, away from edges, and record the readings with the sample.

How a sprayed finish is built, and what gloss shows

A sprayed finish is a stack. On our lacquer page a sealing base coat goes on after preparation, then coats of colour and a top coat, each sanded and de-nibbed between applications, and a mirror gloss is machine-polished to finish. The coating families (water-based, solvent-based, acrylic, polyurethane and melamine) and the Architectural Woodwork Standards systems are compared on the finishes sheet and are not repeated here.

Faults are mostly of three kinds. Each shows more as the sheen rises.

The Wood Handbook says plainly that high-gloss finishes need more attention to the surface because gloss accentuates imperfections, joints above all, and that two pieces of wood will change thickness differently with humidity (pp. 16-29 and 16-30). On a gloss lacquer the board and its edges must be sound: a veneered or MDF substrate is flatter than a timber with open pores (see MDF decoded and edge details). Our journal adds that on a gloss a local repair is harder to hide because it shows in the reflection, so a door or panel is often re-sprayed in full, while matt and satin are more forgiving.

The control sample

The sample is the real specification. The Architectural Woodwork Standards (2009, US) say samples shall be submitted and approved before the finishing of any product, and that the finisher is responsible for meeting or exceeding the control sample for surface performance characteristics such as colour, texture and sheen (Section 5, 4.1.2 and 1.2.12.2.2). For a clear finish on timber they ask for a minimum of three samples to show the colour range and a minimum size of 305 x 305 mm on a panel product. An opaque lacquer has no timber colour range to show, so those sizes are a reasonable starting point, not a requirement.

Approve colour and sheen together, on the real substrate, under the project's lighting, because a colour reads differently at each sheen. Read the gloss with a glossmeter at the stated angle and write the figure on the sample. Keep it as the control for the run and for any later repair. Where the cabinet interior is to be calmer than the exterior, sample both and approve the pair. See sample hierarchy and approval and prototype and mock-up approval. Samples are agreed with the project; this sheet does not offer them on demand.

What to put in the specification

A short list covers it:

1. The system: water-based, solvent-based, acrylic, polyurethane or melamine, and whether it is a two-pack catalysed film (see the finishes sheet).
2. The colour by reference (RAL, NCS or a physical control sample) and the lighting it is approved under.
3. The gloss as a figure in GU, the angle it is read at, the tolerance and where it is read.
4. The substrate: board, veneer or timber, edge treatment, and who fills pores and joints.
5. The faults you will not accept (sunken joints, orange peel, dust nibs, telegraphing, runs) and how far away and in what light they are judged.
6. The sample: one approved sample per colour and sheen, kept as the control.
7. Interior and exterior sheens if they differ, with the pair sampled.
8. Repair and care: the colour reference and sheen kept with the project (see handover and O&M pack).

How you judge a fault matters as much as which faults you name. Write a viewing distance and a light (for example, normal light at [1] m, and raking light for flatness) and apply it to the sample and the work in the same way.

[Two-pack polyurethane] lacquer to [element], colour [RAL / NCS ref] to approved sample [ref], gloss [30 to 40] GU (+/- [ ] GU) measured with a glossmeter at [60] degrees to BS EN ISO 2813 [confirm current edition] on a flat area away from edges, mean of [3] readings recorded on the sample. Sheen to the interior of [units]: [ ] GU, colour as exterior.

Surface to be free of sunken pores or joints, orange peel, runs, dust nibs and telegraphed sanding marks when viewed in [normal light] at [1] m and in raking light at [ ] m. Substrate [MDF / veneered board / solid timber] to be sealed and filled so that pores and joints are not visible. Edges to [radius ref].

One sample per colour and sheen, [305 x 305] mm on the production substrate, sprayed by the production spray shop, to be submitted and approved under project lighting before production. The approved sample, with its colour reference and GU reading, is retained as the control for production and for repairs, and is recorded in the O&M manual.

Standards and sources

• BS EN ISO 2813:2014 Paints and varnishes. Determination of gloss value at 20 degrees, 60 degrees and 85 degrees: BSI Knowledge listing: current, 31 Oct 2014. Standard text not read. The 2000 edition was withdrawn 31 Oct 2014.
• BS EN 13722:2004 Furniture. Assessment of the surface gloss: shop listing only: shown as current, scope not seen. Confirm before citing.
• Architectural Woodwork Standards, 1st edition (2009), Section 5: 1.2.7, 1.2.12.2.2, 4.1.1.3, 4.1.2. US; free section PDFs; grade rules excluded.
• USDA Forest Products Laboratory, Wood Handbook FPL-GTR-282 (2021): pp. 10-16, 16-2, 16-29, 16-30.

Questions we are asked

What is a gloss unit?

A number read on a glossmeter that measures how much light a surface reflects at a stated angle. A specification should give the figure in GU, the angle, the standard and the tolerance.

What gloss is satin?

Our lacquer pages give satin as about 30 to 40, dead matt about 10 and mirror gloss up to about 90. No standard defines the words, so write the number rather than the word.

Which angle do I use?

BS EN ISO 2813:2014 defines 20, 60 and 85 degrees. We did not read the clause on which to use for which range, so ask the workshop which it reads at and state it with the figure.

Why does gloss show so many faults?

Gloss shows the surface in reflection. The Wood Handbook says it accentuates imperfections, especially joints, and large pores can leave low spots under a film unless filled.

Can a gloss lacquer be touched up?

Light marks may polish out, but our journal says a local repair on gloss is hard to hide and a panel is often re-sprayed in full. Matt and satin are more forgiving.

What should the control sample show?

The real substrate, the colour reference, the sheen with its reading in GU, approved under the project's lighting, kept for production and repair.

Is a tolerance published for lacquer gloss?

None was found in what we read. Ask the workshop to propose one and approve it on a sample.