Four things a finish has to survive
Surface coating in a dining room is not a colour decision. It has to survive four separate attacks, and a finish that wins on one can lose badly on another. The first is solvent: 75 percent ethanol hand sanitiser, red wine, vinegar-based dressings and citrus oil, all of which soften the resin rather than the pigment. The second is alkaline cleaner, typically pH 11 to 12 degreaser diluted 1 to 20 and left to dwell for three to five minutes before it is wiped.
The third is abrasion. Dragging a plate 300 mm across a top four times a service, 360 days a year, adds up to roughly 1.4 km of sliding contact per table position per year, and the grit that comes with it does more damage than the plate. The fourth is repairability, and it is the one buyers forget: a finish that cannot be touched up in place, in a room that opens again at eleven the next morning, turns a 40 mm scuff into a replacement top.
Those four requirements pull in different directions. High film build resists abrasion but traps solvent and yellows. Thin films look honest on timber but wear through at the edge first. Cross-linked two-pack systems resist chemistry but cannot be re-melted into the original coat. Knowing which of the four matters most in your room is the only way to choose, and it is rarely the same answer for a table top and a chair frame.
PU lacquer: the working default for timber
Two-pack polyurethane is the standard commercial finish on timber furniture for one reason: it cross-links. The isocyanate hardener reacts with the polyol and the film stops being soluble, so a spill sits on the surface instead of softening into it. Three coats at 30 to 40 microns each give a total dry film of 90 to 120 microns, which is enough to take a 75 percent ethanol wipe held for 30 minutes without a visible change in gloss.
The working properties are what make it practical. It sprays at 18 to 22 seconds in a number 4 cup, sands between coats without loading the paper, and can be repaired by flatting the damaged area with 400 grit, blending a fresh coat and polishing back to the surrounding sheen. On wood restaurant chairs, that repair takes about 25 minutes per chair in a workshop and can be done on site with a touch-up aerosol for small chips.
The costs are cure time and volatility. Full hardness takes about 7 days at 25 degrees C, so a chair packed 24 hours after the last coat will arrive with a film that is still soft enough to print the packing paper into the surface. Solvent content is typically 500 to 600 g per litre, which matters if the project is specifying low-VOC finishes for a green building certification, and the hardener has a 4 to 6 hour pot life once mixed, so a small batch sprayed late in the shift is a batch thrown away.
NC lacquer: fast to spray, first to fail
Nitrocellulose lacquer dries by solvent evaporation in 20 to 30 minutes and burns into the previous coat, which is why it is still common on low-cost furniture and on samples produced to a deadline. It is also the finish most likely to be described only as lacquer on a quotation, with no chemistry named at all, and that omission is worth questioning every time.
Its weakness is exactly what makes it convenient. The film stays thermoplastic, so it re-softens in the presence of solvent. Leave a 60 percent ethanol spill for 15 seconds and it leaves a white ring that does not polish out, and a nightly alkaline wipe will dull the sheen across the whole surface within one season. Total film build is usually 50 to 70 microns, well below what a table top needs, and it is brittle: at 2 to 3 percent elongation before cracking, impact at the edge of a top chips down to bare timber.
The place it gets caught is on a statement piece. The square walnut-top table with pyramid pedestal base finished in NC looks superb in the showroom under warm light, and by month eight the front edge is milky where the sanitiser bottle sits. Ask what the top is finished with in writing. If the answer is lacquer with no further detail, assume NC until a sample proves otherwise.
Water-based lacquer: the compliance answer, with a repair catch
Water-based two-pack systems have moved a long way and now reach 100 to 120 microns of dry film with alcohol resistance close to solvent PU. The headline number is VOC: 30 to 40 g per litre against 500 to 600 for solvent PU, which is the difference between passing and failing an indoor air quality threshold on a project that has one.
The trade is in process control rather than performance. Water-based coats need 4 to 6 hours between coats at 25 degrees C and 60 percent relative humidity, and a workshop running at 80 percent humidity in a Foshan summer will see the film stay soft for 24 hours and blush white if it is pushed. Grain raising is the second issue: the first coat lifts the fibres, so the surface needs a light sand at 320 grit before the second, and skipping that step is how you get a finish that feels rough at 6 months.
Repairability is where it loses to PU. Water-based film does not blend into an aged coat the way a solvent coat does, because the repair relies on a mechanical key rather than partial re-solution, so a patch repair on a visible top usually reads as a patch under raking light. On a project where the restaurant furniture specification calls for low VOC, plan for whole-component refinishing rather than spot repair, and budget the downtime accordingly.
Powder coating: durable until it chips
Metal frames take a different route. Polyester powder is sprayed electrostatically and cured at 180 to 200 degrees C for 15 to 20 minutes, producing a 60 to 80 micron film with no solvent at all and a pencil hardness around 3H. It outlasts any liquid coating on abrasion, passes 100 MEK double rubs without softening, and holds colour in UV far better than a sprayed enamel.
The failure mode is mechanical, not chemical. Powder coat is hard and thin, so it chips rather than scuffs, and every chip is bare steel. In a coastal city with 75 percent average humidity, a 2 mm chip on a leg will show rust at the edges in about 3 weeks, and rust creeps under the film from the chip outward. The same chip on a PU coated timber leg is cosmetic; on powder coated steel it is the start of a corrosion site.
Two specifications change the outcome. First, pretreatment: a zinc phosphate or zirconium conversion coating under the powder is what gets salt spray resistance from 200 hours to 500 hours and beyond, and it is invisible on the quote unless you ask. Second, the contact points. On metal restaurant chairs the frame touches itself when stacked and touches the floor at the glide, and those are where 70 percent of chips begin. Specify replaceable nylon inserts and a stem glide with a 12 mm shank, and keep a touch-up pen matched to the RAL number in the maintenance cupboard. The JP-C079 metal dining chair shows the combination we build to as standard: conversion coated frame, 70 micron polyester film, replaceable glide.
Match the finish to the zone, not to the order
Most projects do not need one finish, they need three. Table tops take the most chemistry and the most abrasion, so they want the highest cross-link density and the thickest film the budget allows: 2K PU at 110 microns, or a compact laminate where the design allows it. Chair seats take abrasion and body oils but little solvent, so a 90 micron PU over a sealed frame is enough. Chair frames and restaurant tables bases take impact and floor contact, which is a powder coat question rather than a lacquer question.
The mistake is specifying one finish across the whole order because it simplifies the purchase order. Dining rooms where the tops are PU and the frames are PU coated steel look consistent and behave inconsistently: the tops survive four years, the frame edges are rusty at fourteen months. Splitting the specification into three lines costs nothing at the quotation stage and is the single change that most extends the life of a furniture package.
Service stations deserve their own line. One stand used for water jugs, cutlery and condiment refills takes liquids on the top surface all day, and a PU film at 90 microns will show ring marks within a year where the same film on a dining top lasts four, because the exposure is continuous rather than occasional. Put a stainless or compact laminate surface there and leave the timber for the room.
How to check finish before the container ships
Finish is the easiest thing to inspect badly, because it looks fine in photographs. Four checks are worth putting in the pre-shipment inspection and they take under an hour on a sample of ten units. Film thickness first: an electronic gauge on a steel frame, or a magnetic gauge over a steel witness plate sprayed alongside timber, should read within 10 percent of the specified 60 to 80 micron range. Below 50 microns, abrasion life falls away sharply.
Adhesion second: a cross-hatch at 1 mm spacing, six cuts each way, tape pulled at 60 degrees. Any film lifted from a square is a pretreatment failure and predicts a chip that takes the coating with it. Solvent third: a cotton pad soaked in 75 percent ethanol, held 30 minutes on a horizontal surface, then examined after 1 hour and 24 hours for softening or gloss change. Cure fourth, and this is the one that gets skipped: ask for the packing date against the last coating date. Anything under 72 hours between them will arrive with print marks.
All four belong in the same document as the load test and the material reports, and a supplier who can produce them without a fortnight of chasing is a supplier who runs restaurant furniture quality control as a process rather than a promise. Ask for the records on the first order, and then ask again on the third, because processes drift once the sample has been approved.