Editing Varnish (section)

===Spar varnish===
''[[Spar varnish]]'' (also called ''marine varnish'' or ''yacht varnish'') was originally intended for use on [[ship]] or [[boat]] [[spar (sailing)|spar]]s, to protect the timber from the effects of sea and weather. Spars bend under the load of their sails. The primary requirements were water resistance and also [[elasticity (physics)|elasticity]], so as to remain adhering as the spars flexed. Elasticity was a pre-condition for weatherproofing too, as a finish that cracked would then allow water through, even if the remaining film was impermeable. Appearance and gloss was of relatively low value. Modified [[tung oil]] and [[phenolic resin]]s are often used.

When first developed, no varnishes had good [[Ultraviolet|UV]]-resistance. Even after more modern synthetic resins did become resistant, a true spar varnish maintained its elasticity above other virtues, even if this required a compromise in its UV-resistance. Spar varnishes are thus ''not'' necessarily the best choice for outdoor woodwork that does not need to bend in service.

Despite this, the widespread perception of "marine products" as "tough" led to domestic outdoor varnishes being [[brand]]ed as "Spar varnish" and sold on the virtue of their weather- and UV-resistance. These claims may be more or less realistic, depending on individual products. Only relatively recently have spar varnishes been available that can offer both effective elasticity and UV-resistance.