Varnishing issues of a serious nature. . . .

[Scuzzie]

I'm an abosute novice in every sense of the word . . . and now a depressed one. . . trying to varnish a door, (about 2ft by 5ft), which is marine ply with a Jarrah border. Put 3 or 4 coats on by roller and got a lot of dimples from the bubbles - friend of mine said never roll varnish for that reason -soooooo - I have brushed another few coats on but always seem to get some imperfection - this time about 2 thirds of the door looks brilliant but the remaining third has wrinkled, (like little mountain ranges) - any suggestions? - oh yeah - using Feast Watson Spar Marine Varnish with dash of Turps - any help will be wildly appreciated

[richardb9]

Hi Scuzzie,
First of all you should have applied a sanding sealer to the door and then sanded this coat back nearly to wood again. If air bubbles were apparent in this first coat, then another should be applied and lightly sanded again. This should seal the timber, and allow you to apply the final coats without any problems. There are special rollers for varnish, and it should be applied rather thickly. Seems like you have a big sanding job ahead to remove most of the initial finish before starting over again
Richard B.

[Scuzzie]

Sanding is underway. . . but as I already have a couple of coats on, do I still need the sealer?

[Ken-67]

You probably need to go right back to bare timber to get a good, fine finish. I usually get good results with Monocel marine varnish. The first coat can be reduced 10% with turps. Subsequent coats should not be thinned. Use a good quality brush. Do not overwork the coats. Sand between coats, preferably by hand, so you can follow the grain.

[soundman]

The sanding sealer issue will be redundant by now as the grain will have been fully choked by the multiple coats.
just sand back till you have a consistent flat and smooth surface.

remember ANY imperfection on a preceeding coat will not be covered by a following coat.

remember with polly U varnishes and paints you must sand if you do not overcoat before the previous coat cures out....for most polly u that is between 24 and 48 hours.....polly u goes thu several curing stages....if you want to overecoat without sanding you must do so before it gets into the second stage.

Now a tip.......give away the turps as the thinner, I have had better results using white spirit.......and that is exactly what i say "WHITE SPIRIT", this is a clean clear hydrocarbon solvent, and unlike turps has no added oil.
I find it behaves more consistently than turps and tends not to cloud the varnish as much in higher thinning amounts.

After you have sanded..wipe down with a lightly moistened with white spirit, clean lint free cloth or paper towel and allow to dry.

Thin every coat of varnish......none of the commercial varnishes that I have encountered flow well off the brush straight out of the tin....they all need thinning.

how much depends on the varnish in question....but you need the varnish to flow out pretty quickly after the brush passes, and you need enough thinner to allow the varnish to stay liquid and keep a wet running edge, so you can work with out the film going tacky while you are still working.

this will vary with the varnish and the weather.

mostly this is between 5% & 10%...if you thin too much you disperse the resins too much and the film wont be as hard and the finish may take on a milky hue.

forget the roller, they are for painters, and i have seen some terible varnish jobs from "painters"

you need a good quality reasonably soft brush, personally I prefeer an oval cutter because it leaves brush track that tapers at the edges.

work with long light strokes, get the volume of the finish on with the first couple of strokes then work it out with the next couple...but do not overwork and do not go back to an area where the finish has started to st up and drag.

Do not apply too heavily or too thinly...just enough to allow the finish to flow.

allow the surface to cure to the point where it is safe to touch and handle before over coating...AND..if there are problems with imperfections fix them before the nextcoat......if that means sanding you may have to allow the finish to set up further.

hope this helps.

cheers

[Arron]

remember with polly U varnishes and paints you must sand if you do not overcoat before the previous coat cures out....for most polly u that is between 24 and 48 hours.....polly u goes thu several curing stages....if you want to overecoat without sanding you must do so before it gets into the second stage.

Hi Soundman, can you elaborate on this comment please. I dont get it.
cheers
Arron

[soundman]

All the single pack poly paints and varnises go thu several phases of curing.

If you leave them too long before overcoating the following coat will not stick properly to the coat below.....this is not universally understood, although it is well documented.

the resins will go off to the extent that they are dry to the touch and can be handled....BUT at this point the solvents in the following coat will soften the previous coat and the two will bond very well.....as time passes the resins continue to cure to a point where the solvents in the following coat will not have this effect on the previous coat..thus the second coat will bond poorly if at all.

I have see clear polly that has been left over a week in hot weather then overcoated without sanding......the bond was soo poor that the top coat could be scraped off with a blunt fingernail.

Different products have this problem to a greater or lesser extent and the time involved varies.

With the "popular brand" of polly U varnish in reasonable weather this point comes at arround 48 hours.

If ya cant get a second coat on within 18 to 24 hours in average weather, best to sand.

cheers