How to apply gloss varnish properly?

[wixy]

I'm having some trouble with applying feast and watson gloss varnish to marine ply that has already been coated with sanding sealer and stained.

So far i've applied 3 coats of the gloss varnish by brush, sanding between coats with 0000 grade steel wool. After a coat has dried, it looks streaky and has bubbles. Then after i've sanded it, most of the gloss disappears.

How can I achieve a smooth finish?

Should I sand after the final coat?

[zitan]

Let me guess the marine ply is either Gaboon or Eucalypt? Both of these are very coarse grained and take a lot of work to get optically flat. A clear epoxy is what is used in the marine/superyacht industry to both seal and grain fill before applying any polyurethane.

Since you've already started applying finish by brush; keep building with heavy unthinned coats, enough where you are virtually swimming in it as you brush. Do this on the level and do it very quickly; you might need three build coats here. You'll find the varnish will self level without brush marks. Let harden for at least two days between each coat. Before the second to last coat sand heavily with 180/220 wet and dry (you can do it with water) until there are no more shiny bits; dust off, flow on the coat, let dry; sand with 600 grit, dust off with the palms of your hands and flow on the final coat.

That how I do it without using grain filler on oak!

[spectre]

Usually streaky uneven finishes are the result of overbrushing or just not putting enough material on the surface. The material hasn't had enough time to flow out after you've finished brushing because its starting to dry already. Have to agree with Zitan it'll take a lot of finish to get the surface looking glassy. I like to use nitrocellulose sanding sealer but that depends on your application requirements.

[wixy]

Thanks for the advice guys.

I bought some wet and dry sandpaper from an auto parts store and gave that a go with water. It seemed to work well, but it's left behind a white chalky residue that won't wipe off. Well, it does wipe off, but then it somehow reappears again a few seconds later.

Any ideas on how to fix this?

[spectre]

Its probably what your surface now looks like when its dry. Give it a wipe over with either a tak cloth or something like a bit of terry with a bit of turps on it, not to much though. Anything thats left behind after that is probably just the surface you're looking at. Also depends just what grit paper you've been using too. You can have something that looks cloudy, clears when wet, and feels smoother than a baby's bum.. if thats how it looks, just get on with the finishing :)

[wixy]

I just gave the turps idea a try, it worked to remove the cloudiness but again only for a few seconds, then it reappears.

I've attached a photo below:

http://img17.imageshack.us/img17/9530/cloudiness.jpg


You can have something that looks cloudy, clears when wet, and feels smoother than a baby's bum.. if thats how it looks, just get on with the finishing :)

So with it looking like this, it's ok to proceed with applying more coats? The cloudiness will disappear for good?

[spectre]

yup, thats just your sanded surface. In sanding it you end up with a surface that isn't smooth hence the cloudiness. Coat it, and that will just disappear permanently. Bare in mind though, if your surface is sanded flat, the whole piece should look cloudy, as it is, you've sanded some of the high points off so it will be better than it was, but it isn't actually a flat/smooth surface yet

[zitan]

Looking good there Wixy; keep on building and sanding until the entire surface is uniformly cloudy after sanding without a single shiny unsanded spot- at this point you know you've bought the film up to a fair surface. See what you're doing now is solely trying to "finish the finish." To get the final coat looking mirror glossy and optically perfect, the second to last coat should be wet sanded with 800-1000 grit only to de-nib any imperfections and dusted with the palms of your hands (if you can feel it's dust free then you know it's dust free). Also, for something multi-sided I'd focus on one face at a time for the final coat so that it can self-level without any runs. Sometimes I've left surfaces for several months just to allow the finish to set hard and shrink into the grain before levelling again. Shellac is notorious for this; and I've heard it can take up to a year to properly finish something like a grand piano with an impossibly thin but impossibly glossy surface! (this is why epoxy is used as a grain filler now since it sets hard in a day and stays that way; only the finish has to be much thicker, and IMHO not as elegant) You can't really buff polyurethane since it stays elastic for a very long time, so the final coat is really the final coat.

I've just done a 2 hour hand-varnishing bodying session today with western red cedar (a lot easier than hardwood).