Tough; flexible; very durable; best levelling varnish on horizontal surfaces
Prone to sagging when applied on vertical surfaces
Wood floors, but not deck surfaces
use to bring out curl or depth in figured woods. Water based varnish, on the other hand, adheres best over water based dyes and stains. If you must use an oil based stain under water-based varnish, it's best to seal the stain with a coat or two of shellac first.
Varnish will cure and adhere to both oily and non-oily woods, with the exception of woods in the rosewood family such as rosewood or cocobolo. These woods contain an antioxidant that prevent varnish from drying. If you want to varnish these woods, first use a sealer coat of shellac.
Varnish is self-sealing, which means you can apply it directly on raw wood without a separate sealer coat. Some woodworkers like to cut their first coat as much as 50/50 with naphtha or mineral spirits so that it will soak in and dry faster. While not necessary, this can be helpful on soft or very porous woods, such as pine and poplar You can omit this thinned coat if you've already treated the bare wood with Danish oil, pore filler, oil stain or wood conditioner.
TYPES OF VARNISH: There are three traditional varnish categories: brushing varnish, spar varnish and urethane or polyurethane varnish. The "poly" varnishes are also divided into subgroups based primarily on intended use. The chart above provides the basic information you need to select the types of varnish for specific finishing jobs.
comments on clarity: Not all varnishes cure to a clear surface finish. Clarity or tone can vary from brand to brand, depending on the oil used to make the varnish. Some polyurethanes are intentionally formulated to be almost colorless, but most varnish has a pleasant honey-amber hue. Spar varnish tends to be darker and redder than the others.
GLOSS, SATIN AND MATTE: All types of varnish are commonly available in these three grades, which refer to the sheen, or gloss, of the cured finish. "Satin" is between the high sheen of gloss varnish and the less reflective, flat finish of matte.
All sheens share the same durability and handling properties, but if you apply too many coats of matte or satin, the clarity of the finish will start to diminish. For a built up finish of three or more coats, it's best to start with gloss varnish then use the sheen of your choice for the last coat or two.
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