Types of Stains and Finishes
Wood stains, which can be oil- or water-based, contain dyes or pigments that soak into the wood to accent the grain. Clear wood finishes—varnishes, shellacs, lacquers, natural oils and water-based finishes—protect wood from moisture or sunlight.
Water-Based Stains
Water-based stains typically emit fewer VOCs, can be cleaned up with soap and water, and dry quickly. However, avoid stains that contain glycol ether solvents, which can be toxic, by asking the manufacturer or checking the MSDS. A clear water-based finish can be used on top of a water-based stain to increase durability.
Natural Oil-Based Stains
Natural (plant-based) oil-based stains are durable and, unlike water-based stains, do not require a sealer. But they may have higher VOC emissions. Oil-based stains with lower VOCs may be a good choice for some projects.
Oil or Synthetic-Based Stains
Oil or synthetic-based stains with acrylic or urethane binders can contain harmful chemicals and release high levels of VOCs. These stains are more water-resistant than water-based stains and are most often used outdoors.
Natural Oil Finishes
Natural oil finishes, like linseed or tung oil, are plant-based and less processed than other finishes. Natural oils provide protection by penetrating the wood, although they are less protective than varnish or lacquer. They often have a lower VOC content compared to varnish, but they may require many coats, take up to a week to dry, and they typically must be reapplied yearly. Note that toxic drying agents such as lead, arsenic, beryllium, chromium, cadmium or nickel may be added to reduce curing time; cobalt and zirconium may also be added, but they are less toxic.
Tung oil cures in a few days and does not usually have added drying agents, but since it comes from nuts, some people may be allergic.
Water-Based Finishes
Water-based stains typically emit fewer VOCs, can be cleaned up with soap and water, and dry quickly. However, avoid stains that contain glycol ether solvents, which can be toxic, by asking the manufacturer or checking the MSDS. A clear water-based finish can be used on top of a water-based stain to increase durability.
Varnish
Varnish—acrylic or urethane—provides the best heat, water and chemical resistance compared to other finishes for indoor projects. However, they contain petroleum and synthetic ingredients that emit high levels of VOCs. They create a long-lasting finish, especially for floors, but require harsh solvents for cleanup. We don’t recommend them for most indoor projects.
Lacquer
WaterAcrylic-based lacquer does not form as hard of a coating as most types of varnish or water-based sealers, often is high in VOCs, and likely contains toluene and xylene solvents.
Shellac
Shellac is a natural resin made from an insect. It has fewer environmental impacts compared to lacquer and varnish, and is a renewable resource. Shellac usually employs ethanol as the solvent, but can be made with methanol, which should be avoided. Shellac dries quickly, but its durability is only fair, so it should be coated with a water-based sealer if used on wood floors in high-traffic areas.
