Polish on paint.

What it sounds like you need is to be sure its bottom does not rub on the ground!

Brian

I hope you used pressure treated timber. If not one of the anti rot solutions (cuprinol etc) Paint these days is crap.

Rain got in to the bottom cross-member as there were places where vertical bars met it. I guess I did not make sure the meeting points were properly sealed with paint. My question was "would coating the final gloss paint with car-wax (or furniture wax) make the whole thing more or less rain resistant? I have memories of putting cellulose paint over polyurethane and seeing it all dissolve before my eyes.

It's generally down to using unsuitable wood for the job. Pretty well all the softwood you can get easily these days ain't up to using outdoors. So will have a short life. Even when well protected.

You certainly get what you pay for with softwood. Joinery quality from a pukka timber merchant is tight grained enough to be virtually waterproof without a finish. That said, no wood will tolerate what they term "prolonged contact" with water i.e. when it collects in grooves or sits on a ledge. The most waterproof substance you can apply to wood is a mineral wax, such as paraffin or microcrystalline. The problem is that it tends to soften in hot weather and has a distinctly cloudy appearance. Possibly it wouldn't notice over white paint

I disagree.

Boatbuilders have gone over to epoxy, almost exclusively.

Andy

Boatbuilders probably have different criteria e.g. appearance and toughness. Fact is, if wood moves, any film will crack. The advantage with waxes is that chemically they don't form a film and they are flexible enough to accommodate any movement in the wood. They also tend to self-heal in warmer weather by softening. When that happens they also pick up dirt and grime so, no, not at all suitable for boats

My original question was for polish on traditional gloss paint. Is car polish (solvent) likely to undo all my hard work?

Depends on the solvent. White spirit won't dissolve paint, but something stronger, like cellulose thinners, almost certainly will.

Would cellulose thinners be used in car polish?

It doesn't tend to last long on a car, though. Are you going to polish this once a month?

Probably not, although cellulose hasn't been used on new cars for many a year.

Most car polishes have a water and detergent solvent base - it's easy to wash the cloths afterwards.

My car polish lasts ages, but no I want to polish it before it goes out newly painted then I shall probably forget about it.

Certainly how I did the few bits of wood that I replaced on mine. Stripped off old wax and wood oil using acetone. Soaked the wood in slow cure low viscosity epoxy then finished it with International Crystal two-pack polyurethane varnish. It lasted for fifteen years in a marine environment with no maintenance. It may have lasted longer - I sold the boat.

Epoxy can't be the final finish. It darkens in uv light, so a polyurethane top coat blocks out the UV and preserves the finish.

Read Steve's description. Not a film.

Andy

Technically it probably is film forming, rather like paint and most other surface coatings. Wax is unique in that the particles stay separate and don't behave like a polymer.