> What are the major differences between traditional (spar?) and
> polyurethane varnish? On this BB some have alluded to differences in
> application and sanding. Which is better and what are the advantages /
> disadvantages to each? Thanks in advance.

Hi,

Chemicaly I have not the faintest idea of the total composition of the products but in aplication they differ as follows:-

Traditional Varnish:

Each coat adhears to the next by what is effectivly a mechanical bond and if one does not abrade the surface poor intercoat bonding is the result.

Polyurathane Varnish:

Each coat is chemicaly linked to the next when applied correctly thus abrading between coats is needed only to improve the flatness of the surface and not to improve the bond. All Polyurathane varnishes and paints I use advise a specific period for overcoating if you exceed this time then a chemical link will not take place only a mechanical bond.

I use both. I find traditional if you have the time and the product (read good woodwork) produces a better visual result. Polyurathane I think is better in terms of lasting power and damage resistance.

Rob