A factory finish on wood millwork sets the colour and sheen the designer chose and protects the wood from hands, cleaners, water and wear. Finishes vary widely in how much abuse they take and how easily they can be repaired, so a reception desk in a clinic needs a different system from a boardroom wall panel. Here is how the common factory finishing systems compare, how to control colour and sheen, and what to write in a specification.
Commercial wood millwork is normally finished in the shop, in a spray booth with controlled temperature, humidity, dust and curing. That gives a more consistent and durable result than finishing on site, where dust, temperature and other trades work against it. Site work by the millwork installer is then limited to filling fastener holes and touching up minor damage with compatible touch-up products. Where any items are finished on site, often by the painting contractor rather than the millwork trade, the colour and sheen still need to match the factory-finished work, which is hard to achieve, so it is worth keeping to a minimum and making clear in the specification who does it.
The 2nd edition of the Architectural Woodwork Standards (Section 5, Finishing) defines thirteen finishing systems by number and name, and specifications commonly name one, for example “System 5, conversion varnish”. Later editions and project specifications may group or number systems differently, so check which edition your project cites. AWI test data, published by the American Hardwood Information Center, rates each system for durability, chemical resistance and other properties. The ones most used on commercial work:
The other systems (latex acrylic, penetrating oil, catalyzed vinyl and cross-linking water-based acrylic) are used less often on commercial millwork. Finish technology and VOC rules change, so check with the manufacturer what they apply and what it is rated for before naming a system.
Wood is natural and varies from tree to tree and board to board, and the same stain looks different on veneer, solid wood, end grain and MDF. The way to control this is with samples:
Where veneer and solid wood meet, such as an edge or frame, the two absorb stain differently, so they may need separate colour adjustment to match. Our article on wood veneer matching covers how leaf layout affects appearance.
Sheen is how much light the finish reflects. It is measured with a gloss meter at a 60-degree angle, in gloss units. The 2nd edition of the woodwork standards uses these ranges: flat 8 to 14, satin 15 to 25, satin gloss 26 to 49, semi-gloss 50 to 70 and gloss 71 to 90. Words like “satin” still mean different things to different suppliers, so the best specification gives a target value or range along with an approved sample. Higher sheen shows scratches, fingerprints and surface flaws more, so matte and satin finishes are the usual choice for heavily used surfaces.
Painted millwork is usually sprayed in the shop with a pigmented catalyzed finish, such as pigmented conversion varnish or lacquer, over a primer. The substrate matters: MDF gives the smoothest result because it has no grain, and the 2nd edition casework section limits Premium-grade opaque exposed surfaces to MDF or MDO. Edges of MDF need sealing and sanding to finish as smoothly as the faces. See cores for commercial millwork for substrate choices. Colour is usually specified by a paint manufacturer’s colour number, with a drawdown or sprayed sample for approval, since the same colour looks different in a millwork finish than in wall paint.
Most finish damage happens after delivery. Finished millwork should be protected until the space is handed over, kept away from wet trades, and installed only when site conditions are right, because finishes can crack or blush if the wood moves or moisture gets in. See site conditions for millwork installation. Agree a touch-up process and who does it, and make sure the touch-up materials match the factory system.
We finish millwork in-house at our Vaughan plant, so colour, sheen and samples are managed in the same place the pieces are built. The finishing system, colour and sheen for each project are confirmed through shop drawings and finish samples submitted for review and approval before production. Send us your finish schedule and we will come back with any questions on the system, colour or sheen.
In AWI test data, UV-cured finishes, catalyzed polyurethane and catalyzed polyester rate highest for durability and chemical resistance, with conversion varnish close behind. Conversion varnish and UV-cured finishes are the common choices for heavily used commercial casework because they balance durability with practical application and repair.
Precatalyzed lacquer has the catalyst added by the manufacturer and is ready to spray. Postcatalyzed lacquer has the catalyst added just before use, which gives higher heat and chemical resistance but a limited working time once mixed.
As a target gloss value or range measured with a gloss meter at 60 degrees, together with an approved sample. The 2nd edition of the woodwork standards defines satin as 15 to 25 gloss units and semi-gloss as 50 to 70, but terms vary between suppliers, so a number and a sample avoid disputes.
Wood varies naturally, and stain looks different on veneer, solid wood and end grain, and under different lighting. Approving a range of samples on the actual species and cut, and checking them under the project lighting, sets realistic expectations.
In the shop wherever possible. Factory finishing in a controlled spray booth gives a more consistent and durable result. Site work is best limited to filling, touch-up and any field-applied trim.
