: He emphasized that we should be using two-part
: linear polyurethane, the latest and greatest UV block that according to
: him...is far superior to varnish. Does anyone know anything about this
: stuff?

Hi Bob,

2 part polyurethane is far superior to varnish. What varnish has going for it is ease of application and one only needs a charcoal respirator to apply it.

The polyurethane is far more toxic and charcoal respirators do not filter out the isocyanates used in the hardener.

Durability is where polyurethanes really shine. (Actually they really shine in the shine department too!) Polyurethanes have very high chemical and UV protection as opposed to varnish which has almost no chemical resistance and only moderate UV protection. (Try spilling laquer thinner on varnish and polyurethane.) If you leave both out in the sun everyday polyurethane has a life expectancy of about 10 years, I don't know what it is for varnish but I hear many say they recoat every 2 years on kayaks which spend most of their time out of the sun.

The biggest drawback to polyurethanes is their toxicity and what these toxins do to you and others in the vicinity. There are ways to address the problems which you have probably read in the archives.

Hope this helps,

Ian