Metal finishes for luminaires: brass, nickel, chrome, bronze, plated, PVD and lacquered

At a glance

Basis: a conservation body note, one lacquer maker's data sheet and our sheets on PVD, plating and lacquer. No source gives a life in years. Finish names vary: approve a physical sample.

Four ways a luminaire stresses its finish

A table leg is handled, wiped and occasionally knocked. A luminaire is all of that, plus four stresses of its own. The drawing marks them on a wall light; a chandelier arm or a pendant canopy has the same zones in different places.

• Heat (1). The lamp holder and the base of the shade run warmer than the rest of the fitting. One lacquer maker’s data sheet types its product as a thermoplastic acrylic, a plastic that softens when heated, and we found no service temperature in it. No source we read gives a heat limit for any decorative finish. Ask the partner workshop for the surface temperature at the lamp holder with the specified lamp and driver, and for the finish’s rated limit.
• Touch (2). Switches, pull cords, arm joints and shade rims are held many times a day. The Canadian Conservation Institute, writing about brass and copper, lists grease, dust and fingerprints as sources of corrosion and says gloves stop the moisture, salts and oils of the fingers reaching freshly cleaned metal. It calls lacquering “a tacit acceptance of a failure in other areas of protection”, handling among them. In a hotel the hands cannot be removed, so the finish at the touch points is the decision.
• Damp (3). In a bathroom the finish meets steam, splashes and sprays, and the fitting’s IP rating and base metal matter more than the surface. Some brasses lose zinc in water: see brass alloys explained. On a plated part, damp reaches the base wherever the plating is thin or broken.
• Cleaning (4). Housekeeping cloths and sprays pass over the tops of arms and shades. One lacquer data sheet lists ketone solvents such as acetone, and xylene and toluene, among the ways to strip its lacquer, so a solvent spray is not a cleaner for lacquered brass. The conservation note adds that polishing is abrasive and removes tarnish and some surface metal. See cleaning and maintaining metal finishes.

What is under the finish

Every plated or coated finish is a stack: a base metal, sometimes an undercoat, a thin finish and often a clear seal. What sits under the top layer decides what you see when it wears and whether it can be put right. The drawing shows six systems without thicknesses, because the films are far thinner than the base and none can be read off a finish name. The figures, with their gaps, are on the plating and coating thickness sheet.

• Solid metal has nothing to wear through: the same metal shows all the way down, and re-polishing removes some of it.
• Plated or coated parts show the layer beneath at edges and touch points. Ask what the base metal is, whether there is a nickel layer, and the certified minimum thickness.
• PVD follows the surface beneath exactly, so the base finish decides the look, and a damaged area cannot be touched up on site: see PVD coatings explained.
• Earthing. Where a fitting relies on its metalwork for the earth connection, a coating or lacquer can insulate. Ask the workshop how the finish is removed or bridged at earth points. The luminaire standard, BS EN 60598-1, governs it and was not read.

How each finish ages, and what the sources say

• Unlacquered brass and bronze. Some tarnish is stable: the conservation note says many items acquire a stable tarnish in use. Polishing is an abrasive operation that removes some surface metal, and repeated polishing loses surface detail. A wax coat gives some protection against the environment and handling and comes off with mineral spirits. This is a living finish: the client should choose it knowingly, and the operator should be told. See lacquered vs unlacquered brass and copper.
• Lacquered brass. The conservation note says no matter how well lacquer is applied it always alters the look, and that it is difficult to remove. One lacquer data sheet asks for a dry film of 1.0 to 1.5 mils (about 25 to 38 micrometres) built in thin coats, application within an hour of cleaning to a dry surface or clouding occurs, and 2 to 3 days minimum cure before exposure, 7 recommended. A part lacquered in a damp workshop, or re-lacquered on site, may not match the factory film. We found no independent test of how long lacquer lasts under hotel handling.
• Nickel and chrome. A bright nickel and chromium plate is a thin chromium film over a nickel layer on the base metal. When it wears, the nickel or the base shows. The minimum thickness depends on the service condition class in BS EN ISO 1456, which we did not read: ask for the class and the certified minimum.
• Aged or antique brass and bronze. The colour is a surface treatment, applied chemically or relieved by hand so that highlights show where wear would put them, then sealed or waxed. Copper alloys keep ageing under the seal. A fresh patina applied on site is described by fabricators as extremely difficult, so spares and later additions need the same batch. See patination of brass, bronze, copper and steel.
• PVD. A very thin, hard film that follows the surface beneath. It is described as much more scratch resistant than electrochemical colouring, and damage to it cannot be repaired.

No finish here has a life in years that we can quote. How long a finish lasts depends on the environment, the handling and the maintenance, and none of the sources we read gives independent figures for a hotel luminaire. Treat any quoted number of years as a guess.

Matching, pairing and the lamp

• Finish names are not standards. ‘Antique brass’, ‘satin nickel’ and ‘bronze’ mean different things at different finishers. Approve a physical sample, signed and dated, and match the luminaire to the door furniture, taps and handrails against that sample, not against a name. See ironmongery finish codes and sample approval and batch variation.
• Spares and later additions come from another batch. Ask for the colour tolerance between batches in writing, and order spare touch-point parts (switch plates, pull-cord bangles) with the first batch.
• View the sample under the specified lamp, at full output and at the dimmed levels it will run at. Colour temperature and dimming change how a warm metal reads, and a dim-to-warm source shifts as it dims; we found no source that quantifies the effect on a finish. See colour temperature by space.
• Put the finish beside the glass. A brass or nickel frame reads against the glass colour next to it: see Murano glass colour.

What to ask the partner workshop

• Base metal and alloy for each part (see brass alloys explained).
• Finishing system, each layer in order, its certified minimum thickness in micrometres and the standard it is measured to.
• Corrosion or abrasion test evidence at the level claimed, named and dated, and the colour tolerance between batches.
• Surface temperature at the lamp holder with the specified lamp and driver, and the finish’s rated limit.
• How the finish is removed or bridged at earth connection points, where metalwork carries the earth.
• The repair route for each finish: re-lacquer, re-plate or replace the part, and whether it is a site or a workshop job.
• A care sheet for each finish, named by finish, for the handover file.

Fitting [ref]: base metal [solid brass CW508L / mild steel / stainless steel 316]. Finish [unlacquered brass / lacquered brass / satin nickel plate / PVD [colour] on [stainless steel 316] / antique brass, chemically darkened then [waxed / lacquered]]. Each layer in order with its certified minimum thickness [ ] micrometres, measured to [standard], stated on the shop drawing. A finish name alone is not accepted.

Finish approved on physical sample [ref, date, signed], viewed under the specified lamp [CCT, CRI] at [full and 30] per cent output beside the glass sample [ref]. Production within the approved range; spares and later orders batch-matched, with the colour tolerance between batches stated in writing.

Finish suitable for the surface temperature at the lamp holder and shade ring of [ ] degrees C (workshop to state it for the specified lamp and driver, with the finish's rated limit) and for IP rating [ ] in [zone]. Where metalwork carries the earth, the finish is removed or bridged at earth points; the workshop confirms how.

Care sheet for each finish, named by finish. Living finish accepted by [client]: the fitting will change colour with handling and time, as intended. [ ] sets of touch-point parts in the same batch. Repair route per finish [re-lacquer / re-plate / replace part; site or workshop] stated by the workshop.

Standards and sources

• Canadian Conservation Institute, CCI Notes 9/3: Brass and Copper (cleaning, polishing, waxing): read.
• One lacquer maker's data sheet (clear acrylic brass lacquer): read. PVD, thickness and alloy points are carried from our sister sheets. BS EN ISO 1456, BS EN 60598-1 and ISO 9227 are named only, not read.

Questions we are asked

Is lacquered or unlacquered brass better on a light fitting?

Neither: they are different decisions. Lacquer slows tarnish and holds the polished look while the film is intact, but it always alters the look a little, can wear where it is handled and is hard to remove. Unlacquered brass changes with handling and time, which can be the point. Where hands land, at switches and joints, either needs a plan. Write the client's choice into the specification and give the operator a care sheet.

How long does a metal finish last on a light fitting?

We found no independent test that says. It depends on the environment, the handling and the maintenance. Be wary of any guarantee quoted in years; ask for the finishing system, the certified minimum thickness and the repair route instead.

Can PVD be applied to brass?

One coating house's datasheet lists stainless steel and titanium as taking PVD directly, and brass, aluminium, zinc die-cast and ABS as needing a nickel and chrome plating first. See the PVD sheet. Damage to a PVD finish cannot be repaired on site.

Is nickel or chrome better in a bathroom?

No source we read ranks them. In a bathroom the fitting's IP rating and its base metal matter more than the surface, and both finishes are thin plated layers that show the metal beneath when worn. Ask for the plating class and certified minimum thickness, and have the electrical designer confirm the zone.

How do I match a light fitting to the door handles and taps?

Finish names differ between finishers, so match by physical sample, not by name: approve one sample, signed and dated, and hold every supplier to it. Ask each for the colour tolerance between batches and order spares in the first batch.

Does the lamp change how brass or bronze looks?

It can. Colour temperature and dimming change how a warm metal reads, so view the sample under the specified lamp at the levels it will run at. We found no source that quantifies the effect.