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Varnish and rubbing out

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Forum topic by Flanders posted 07-24-2016 01:46 PM 457 views 0 times favorited 14 replies Add to Favorites Watch
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Flanders

3 posts in 137 days


07-24-2016 01:46 PM

Hello fellow wood workers!!

New ti the forum and look forward to learning lots!

My question is about rubbing out a finish. Im using Saman hybrid varnish, 4 coats, followed by ample dry time. I’ve done this on 3 separate projects and am sick of always sanding through.

I use a 400 grit, sand down to the valleys, then soapy water with 600 grit and find the wood starts the swell due to the water.

I’ve watched countless videos, used uo to 8 coats on one project, sanded as minimally as possible by hand but still sand through.

Any suggestions to prevent sanding through? Different varnish? The rest of the project jasnt been sanded yet, just the playing surface, its a chess board. Maple, walnut and padauk. The padauk sits 3/4” lower.


14 replies so far

View jdmaher's profile

jdmaher

384 posts in 2045 days


#1 posted 07-24-2016 04:31 PM

What do you mean by “sand down to the valleys”?

Perhaps you are trying for a much more refined finish than I usually try. Overall, your description sounds like you are sanding too much. To my mind, WAY too much.

Between coats, I sometimes will lightly pass 400 grit over a coat, just to remove dust nibs. Like, one or two passes, with the grain, no pressure. Then, I vacuum, then wipe it off with a dampened cloth to make sure I get the sanding dust. Then the next coat. Final coat I might “rub” with kraft paper (brown paper bags).

It sounds like you’re seeing brush strokes and trying to level them out between each coat? I haven’t tried Saman, but with most finishes I just use cheapo foam brushes and rely on self-leveling.

Using a lubricant (like water) with high grit paper sounds like a “french polishing” technique, but I have never tried that.

-- Jim Maher, Illinois

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Flanders

3 posts in 137 days


#2 posted 07-24-2016 04:39 PM

Thanks for the reply!!

By valleys I do mean the lowest point in the brush strokes. Im only sanding after the last coat.

I’m trying to get a nice high gloss finish like a guitar.

Though I think you are probably right, I must be sanding too much.

View Ger21's profile

Ger21

1047 posts in 2596 days


#3 posted 07-24-2016 04:55 PM

Try thinning the varnish so it goes on smoother, without the deep valleys you have.
If you have really deep brush marks, you’re always going to have a problem sanding and rubbing out.
With a thicker finish like you’re using, there’s no need to wet sand between coats. And 220 or 320 is all you should need. No need to go to 400 grit between coats.

For the final coat, I’d try to apply 2-3 coats so you have more material for the final sanding.
Apply each coat when it gets tacky. Spraying would make this a lot easier.

-- Gerry, http://www.thecncwoodworker.com/index.html http://www.jointcam.com

View jwmalone's profile

jwmalone

769 posts in 168 days


#4 posted 07-24-2016 05:01 PM

Yes to much sanding, jdmaher has it right. But I don’t use those foam brushes, doesn’t matter if its a chess board or a fine sailing vessel I use a good china bristle brush (personal preference), applying varnish (generic term) is an art form and not really that hard. AS jd also mentioned self leveling will take care of most your problem, I believe musical instrument are usually sprayed, I could be wrong, but the same look can be achieved with a brush, You may also be applying to thin of a coat. One more thing stick to the old school stuff all these hybrid this polly that ect..ect.. are just new twist on some very basic products that have been around for ever. I am a painter by trade, learned wood finish’s from cabinet makers and woodworkers, paint manufactures are the sorriest sobs out there when it comes to marketing. do the research, and take all this advice from some of these ppl with a grain of salt its not that complicated once you understand the very basics. good luck , have fun

-- "Boy you could get more work done it you quit flapping your pie hole" Grandpa

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jwmalone

769 posts in 168 days


#5 posted 07-24-2016 05:10 PM

Oh, what kind of brush are you using Brushes and the filaments and their tip designs are very important you have to match it to the product you’re applying. something with a srt solid round taper will leave lots of brush marks in slow leveling paints, you need something with flagged tips like china bristle.

-- "Boy you could get more work done it you quit flapping your pie hole" Grandpa

View JBrow's profile

JBrow

818 posts in 385 days


#6 posted 07-24-2016 05:26 PM

Flanders,

In addition to comments so far… I use a foam brush. I apply finish to a small area focusing initially on just getting the varnish on quickly. Then, I go back and take leveling strokes which are single brush strokes the full length of the area where finish was just applied. I do not visit the area after the leveling strokes again. I continue applying varnish from the wet edge; the area where the last leveling stroke was made.

If the varnish remains on the project too long before the leveling stroke, too much solvent may evaporate from the finish, diminishing its ability of the varnish to self-level and thus leave brush marks behind. Too long can be different times and depends on the ambient temperature and humidity. When it is hot and/or dry, too long may be a minute or two after the varnish is first applied, whereas when it is cool and/or humid, too long may be as much as 3 to 5 minutes.

View AlaskaGuy's profile

AlaskaGuy

2406 posts in 1774 days


#7 posted 07-25-2016 01:10 AM

I’m no finishing expert by a long shot. That being said what are you trying to achieve buy rubbing out”.

Are you waiting for the finish to ’’fully cure’’ as opposed to ’’fully dry before you start rubbing out?

-- Alaskan's for Global warming!

View Flanders's profile

Flanders

3 posts in 137 days


#8 posted 07-25-2016 02:26 PM

Thanks again all for the replies!!

I went out and bought a china bristle brush, it does seem to help with the brush strokes, but for some reason doesn’t hold as much varnish. Maybe I was applying too much with the foam brush, but then again, I wasn’t getting the orange peel effect with the foam brush.

I also am applying it rather quickly, then doing a single leveling out stroke which also seems to help.

@AlaskaGuy What I’m trying to achieve is a nice mirror like finish to the surface of the chess board. The first time round I had left it for 1 week before doing anything more to it. This next time it will be left for 2 weeks due to work scheduling so the varnish itself should be good and cured!

Thanks again all, I’ll try and keep you posted!!

View DrDirt's profile

DrDirt

4169 posts in 3207 days


#9 posted 07-25-2016 08:24 PM

Agree with Gerry – I only rub out the final coat. ideally the next coat fills the valleys of the prior coat such that when you level the final layer, you don’t rub through.
I have burned through the finish before, and made a ‘light spot’ -but I never experienced swelling from wet sanding.

do you know what your film thickness is? I see you mentioned going up to 8 coats, but I am wondering what is the “expected” build of the finish layer. Some oil finishes (oil varnish blends/wiping varnishes) hardly build up at all and are easy to burn through. It is also why they dry so quickly, they have a lot of solvent vs solids
You may have to make some calls to their tech support line – as most makers don’t supply the instructions for “finishing the finish” they will just say “2 coats and it will look good for a lifetime”

-- 'Political correctness is fascism pretending to be manners' ~George Carlin

View OSU55's profile

OSU55

1060 posts in 1455 days


#10 posted 07-29-2016 02:15 AM

You may be allowing ample “dry” time, but 1 week or 2 weeks is not enough “cure” time for OB varnish, not with enough film thickness to get a “piano” gloss finish. 30 days minimum in a hot garage will do nicely. The less time it’s allowed to cure, the more likely the grain will telegraph through after a few months. Let it dry a few days and do a “rough” sanding with ~400, if all looks good, set it aside for another 3 weeks or so, then finish out.

I much prefer spraying WB finish when doing a fully filled finish. With the poly I use, additional coats burn in for 24 hrs after the 1st coat, so no knit lines to worry about. The WB lacquer will burn in anytime, just like solvent lacquer.

View jwmalone's profile

jwmalone

769 posts in 168 days


#11 posted 07-29-2016 02:33 AM

Orange peel, that’s an indication of a major problem if you’re using a china bristle brush and varnish (any type). Something you’re using is not compatible, or your technique is all wrong. again research.

-- "Boy you could get more work done it you quit flapping your pie hole" Grandpa

View DwightC's profile

DwightC

26 posts in 241 days


#12 posted 07-29-2016 05:09 AM

I hope you are doing all this experimenting on sample boards, and not on projects nearing completion. There’s a lot of good information in this thread but none of us have seen what you’re working on, of course, so you really have to filter what we have to say. The advantage to using sample boards is that you can try different approaches a lot more efficiently (they do need to be sanded to whatever grit you’re going to with your project).

To echo an earlier observation—there is a world of difference between time to dry and time to cure and if you are ‘finishing the finish’ (to borrow the title of a chapter of Flexner’s excellent tome on finishing), time to cure is what you’re concerned with. That is product specific, and depends on your local conditions, too. One final thought—when things have gone well to the point that you are just working on your topcoat, Abralon pads can be real useful (1000 grit for a matt finish, 2000 and up for gloss). You can develop some real depth using them.

View DrDirt's profile

DrDirt

4169 posts in 3207 days


#13 posted 08-03-2016 08:23 PM



You may be allowing ample “dry” time, but 1 week or 2 weeks is not enough “cure” time for OB varnish, not with enough film thickness to get a “piano” gloss finish. 30 days minimum in a hot garage will do nicely. The less time it s allowed to cure, the more likely the grain will telegraph through after a few months. Let it dry a few days and do a “rough” sanding with ~400, if all looks good, set it aside for another 3 weeks or so, then finish out.

I much prefer spraying WB finish when doing a fully filled finish. With the poly I use, additional coats burn in for 24 hrs after the 1st coat, so no knit lines to worry about. The WB lacquer will burn in anytime, just like solvent lacquer.

- OSU55


But if you are ‘burning through’ 8 coats, while wet sanding with 400 grit.. semms there must not be much of a layer.
I would test “dry sanding” with 400 and see if you get white powder… of if your paper is all filled with corns.
If it is powder – it is cured enough to rub out.
I have never needed more than 7 or 8 days for varnish to cure enough to level… indeed it will continue to cure and polymerize/cross link for a month..

-- 'Political correctness is fascism pretending to be manners' ~George Carlin

View OSU55's profile

OSU55

1060 posts in 1455 days


#14 posted 08-04-2016 01:38 AM

I stated a finish thick enough to rub out, and the reason for allowing a longer cure time is to prevent telegraphing grain/imperfections through, not that it cant be done sooner.

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