There are two-part finishes available for timber. Plasticote (or some such spelling) makes a finish that we sometimes use for kitchen worksurfaces that will get a proper soaking. Who knows what it will be like outdoors years from now.
Ditto what Colin says about Polyvine.
Technically, scientifically, I have no idea what UV filters are. The energy of ultraviolet light either has to be reflected, as much of it is in white gloss paint, or absorbed, as much of it is in black paint and clear varnish. If absorbed, the energy is either dissipated harmlessly or it causes damage. I assume that "UV filters" are particles or chemicals added to varnish that will help absorb the energy harmlessly or perhaps even reflect it like tiny mirrors. And my hunch is that they aren't available for all types of finish and aren't particularly effective at the best of times. Pigments or paint solids are good at taking the damage, so paint lasts much longer than varnish. Different resins, natural or man made, will be more or less resistant to damage.
Old fashioned is not necessarily bad. Plant resins are far better at withstanding ultraviolet light than are complex manufactured polymers. Plant rubber is better than butyl rubber, but butyl is almost indestructible by light compared to polythene. But if you wish to line your pond, your choice is butyl or polythene and not a plant rubber product, it just isn't made. Similarly with wood varnishes, the natural plant products are all but gone and you are left with cheap linseed oil. An expensive alternative is the base oil used in linseed oil paints at www.linseedpaintcompany.co.uk. It will survive a good few years.
The easy option is to use a modern product that is recommended by professional painters who have seen with their own eyes that it works. I can swear that yacht varnish (spirit based polyurethane) manufactured by global industrial paint giants and sold in national diy centres will last beautifully for a whole year. If you are hoping for something that lasts longer, don't trust the manufacturers' word, trust someone who finishes exterior joinery for a living.
Ditto what Colin says about Polyvine.
Technically, scientifically, I have no idea what UV filters are. The energy of ultraviolet light either has to be reflected, as much of it is in white gloss paint, or absorbed, as much of it is in black paint and clear varnish. If absorbed, the energy is either dissipated harmlessly or it causes damage. I assume that "UV filters" are particles or chemicals added to varnish that will help absorb the energy harmlessly or perhaps even reflect it like tiny mirrors. And my hunch is that they aren't available for all types of finish and aren't particularly effective at the best of times. Pigments or paint solids are good at taking the damage, so paint lasts much longer than varnish. Different resins, natural or man made, will be more or less resistant to damage.
Old fashioned is not necessarily bad. Plant resins are far better at withstanding ultraviolet light than are complex manufactured polymers. Plant rubber is better than butyl rubber, but butyl is almost indestructible by light compared to polythene. But if you wish to line your pond, your choice is butyl or polythene and not a plant rubber product, it just isn't made. Similarly with wood varnishes, the natural plant products are all but gone and you are left with cheap linseed oil. An expensive alternative is the base oil used in linseed oil paints at www.linseedpaintcompany.co.uk. It will survive a good few years.
The easy option is to use a modern product that is recommended by professional painters who have seen with their own eyes that it works. I can swear that yacht varnish (spirit based polyurethane) manufactured by global industrial paint giants and sold in national diy centres will last beautifully for a whole year. If you are hoping for something that lasts longer, don't trust the manufacturers' word, trust someone who finishes exterior joinery for a living.
