|Forum topic by Steven H||posted 05-15-2011 08:34 PM||7186 views||0 times favorited||18 replies|
05-15-2011 08:34 PM
Varnish is made by mixing and heating a resin (could be alkyd, phenolic or urethane or combination) and a drying oil (typically linseed oil, soya oil or sometimes tung oil) until the two become a new compound called “varnish”.
Polyurethane (also known as Urethane)
Urethane resin is very inexpensive produce than the others, making it lowesr price resin for the manufactor. It’s somewhat greater scratch resistance and heat resistance. This varnish is the most durable than other two, however it is not hard. Its a choice for children’s furniture, kitchen tables, and other subject to having abuse across the surface. It has taken over the varnish market. Polyuerthane is common found at home centers.
Alkyd resin is used to make lacquer and oil-based paint. The primary attribute of alkyd resin is its superior clarity. Makes it an excellent choice, when combined with soya oil, as a finish for fine furniture. Alkyd resin varnish made from soya oil produces a very warm, clear finish that is quite color stable over time. Manufactor add some Allkyd resin to polyurethane to reduce it from yellowing.
Spar Varnish is same thing Marine Varnish.
It is commonly found in Marine stores. Spar Varnish is cooked with higher percentage of oil than Resin. The reason is because it is to let it to be flexible and soft in the sun. NOT ALL Spar Varnish are created equal. The Spar Varnish sold at home cetner like Minwax are not as good as you think. From What I known it contains poluyurethane and and UV inhibitors. This is a poor choice for exterior. While many of these products contain UV inhibitors, the better marine varnishes do not. They rely instead on the highly reflective nature of the finish film to deflect the damaging rays of the sun. This property places a much higher premium on regular maintenance to maintain the finish. However all finish do not last out door, so they need regualr maintanence.
A high quality Spar varnish can cost around $40-50.