The sheen of a finish is the degree of light reflection when a surface is viewed at a low angle. In a high sheen or high gloss surface, you see glare or a distinct reflected image. In a low sheen, satin or flat surface, glare and reflection are softened to the point of non-existence.
- Flatted finishes (left) produce little or no reflection while gloss finishes with no flatting agent added (right) reflect glare and image
Oil finishes always produce a softened satin sheen. Wax finishes produce a little more shine than oil. All film-building finishes—varnish, lacquer, water-based finish and shellac—can be made to have any sheen, from high gloss to very flat.
There are two ways to produce a flatted sheen: rub the finish with abrasives of various grits to produce the sheen you want, or use a finish with the sheen already built in by the inclusion of a “flatting agent.” Varnish (including polyurethane varnish), lacquer and water-based finish are available in several sheens. Shellac is supplied only in gloss.
Both methods of creating a flatted sheen—rubbing with abrasives and using a product containing flatting agent—work by creating a microscopically rough surface that reflects light randomly.
This article is about the role of flatting agent and how it works.
