Hardwood Floors June/July 2018

AT THE SITE

Stains and Colorants (Continued)

(higher solid content) a bit more challenging to properly apply; meaning more physical work required to assure not too much product/resin is left on the stained substrate. Also, this results in extended drying time before a finish-coat may safely be applied. Generally, oil-based stains provide longer “open-time” and are the easiest with which to work. Linseed oil type stains generally give more open time and dry a bit slower than the alkyd/urethane type (“quick dry” versions). Additives in oil-based stains would be, for example, the drying agent; they are often metallic salts and may be referred to sometimes as siccative (driers). This additive in the formulation accelerates the reaction of the binder with oxygen once it has been applied (after the solvents evaporate), so an oil-based stain is therefore called an oxidative drying product. Once applied, and the solvent has evaporated, it is important to provide good airflow/oxygen. When the binder/resin of a stain is water soluble (latex/acrylic binder) by its own nature, a stain would be categorized as a waterborne stain. Waterborne stains are much different to work with in comparison to oil-based stains due to the shorter open-time and overlapping effects which may create lap marks. Waterborne stains are also very low VOC and are becoming more prominent as VOC regulations continue to tighten up. Waterborne stains are less harmful to the environment and to the individual applying it. Waterborne stains do require learning new application methods, but offer many color, application, and health benefits otherwise very difficult to achieve. DYES Dyes are different compared to wood stain and are the oldest known coloring agents. Dyes are mentioned in the Bible, and written history proves that as far back as 2600 B.C., organic dyes were used in China. In the olden days, they were extracted from roots, nuts, fruits, bark, and insects yielding nice colors that were very transparent but exhibited very poor lightfastness. In the mid-1800s, a big breakthrough occurred by accident and a new “dye stuff” was discovered by experimenting with coal tar (with a poisonous coal tar byproduct called aniline), the dye stuff derived from this is also known as aniline dye. This product was more lightfast than organic dyes; this is when the development of new synthetic (non-organic) dyes started. Dyes were primarily used for dyeing fabrics, but later in the 1800s, woodworkers also started using them because of the tremendous transparency and better lightfastness compared to organic dyes. Dyes are many times finer in particle size (at a molecular level, you may compare it as a needlepoint versus a football) compared to pigments, so that is a huge advantage if one wants to maintain the best possible clarity when coloring wood. Dyes completely dissolve in a solvent where pigments don’t.

Oil-based stain

Aniline dye

Chemical reactive

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