Using lacquer for piano finish on veneer? - Woodworking Talk - Woodworkers Forum
 
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post #1 of 5 Old 04-30-2012, 10:09 PM Thread Starter
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Using lacquer for piano finish on veneer?

I've been having a lot of trouble with finishing, so any suggestions are welcome. The project is a pair of speakers covered with walnut burl veneer. Basically MDF boxes, no curves. I really want a totally smooth piano finish that highlights the grain.


Minwax brushed satin lacquer appeared to be the best looking finish. The problem is I need to brush on 7-12 layers of lacquer and let it cure before I can sand/polish it and get that smooth finish. I am afraid that no matter how much time I let it cure it will eventually cut back into the grain and be visible. A test piece supported this fear, sanding after about 4 weeks, although the cut back seemed relatively small several months later it was present. All grain filling techniques I've tried have been subpar (can go into these if you'd like), bringing me back to lacquer, and my question. I am looking for a finish to last 20ish years. Could it be possible to brush on 10+ layers of lacquer and wait 8 weeks (or more) for it to cure, or is the cut back just an impossible battle to win? Would applying a shellac sealcoat first help minimize it? Any other suggestions for what to try, or other issues besides cut back I may not realize?
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post #2 of 5 Old 05-01-2012, 04:52 AM
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Quote:
Originally Posted by superapplekid View Post
I've been having a lot of trouble with finishing, so any suggestions are welcome. The project is a pair of speakers covered with walnut burl veneer. Basically MDF boxes, no curves. I really want a totally smooth piano finish that highlights the grain.


Minwax brushed satin lacquer appeared to be the best looking finish. The problem is I need to brush on 7-12 layers of lacquer and let it cure before I can sand/polish it and get that smooth finish. I am afraid that no matter how much time I let it cure it will eventually cut back into the grain and be visible. A test piece supported this fear, sanding after about 4 weeks, although the cut back seemed relatively small several months later it was present. All grain filling techniques I've tried have been subpar (can go into these if you'd like), bringing me back to lacquer, and my question. I am looking for a finish to last 20ish years. Could it be possible to brush on 10+ layers of lacquer and wait 8 weeks (or more) for it to cure, or is the cut back just an impossible battle to win? Would applying a shellac sealcoat first help minimize it? Any other suggestions for what to try, or other issues besides cut back I may not realize?





You mention that you want a 'piano' finish, but say you used a satin lacquer. Do you want that super high gloss reflective finish, like a piano finish, or just a smooth to the touch finish?

Did you use a grain filler specifically for that purpose, like ones called a paste wood filler, or 'grain filler'? They apply in a consistency of mayonnaise.









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post #3 of 5 Old 05-01-2012, 05:03 AM
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Quote:
Originally Posted by superapplekid View Post
I've been having a lot of trouble with finishing, so any suggestions are welcome. The project is a pair of speakers covered with walnut burl veneer. Basically MDF boxes, no curves. I really want a totally smooth piano finish that highlights the grain.


Minwax brushed satin lacquer appeared to be the best looking finish. The problem is I need to brush on 7-12 layers of lacquer and let it cure before I can sand/polish it and get that smooth finish. I am afraid that no matter how much time I let it cure it will eventually cut back into the grain and be visible. A test piece supported this fear, sanding after about 4 weeks, although the cut back seemed relatively small several months later it was present. All grain filling techniques I've tried have been subpar (can go into these if you'd like), bringing me back to lacquer, and my question. I am looking for a finish to last 20ish years. Could it be possible to brush on 10+ layers of lacquer and wait 8 weeks (or more) for it to cure, or is the cut back just an impossible battle to win? Would applying a shellac sealcoat first help minimize it? Any other suggestions for what to try, or other issues besides cut back I may not realize?
If money is no object, i would use 2 component urethane instead of lacquer. If you don't have 200.00+ then i would use WW conversion varnish, or 3rdly post cat lacquer. If you are not set up to spray these yourself, i would then take them to a cabinet shop or with the 2K, to an automotive shop and get an estimate on having professionally done.

Again, if you can't afford any of these methods or materials and can only do it yourself by brush, i would then recommend the fast dry poly instead of the brushing lacquer. Build with gloss and apply the satin or semigloss as the final coat or two. Poly doesn't remelt like lacquer does so once it's cured hard, what you see is what you get.

One of the most important factors for a glass like level surface is making sure the substrate wood/veneer. is as flat as glass before applying any finish!! If not, any surface anomalies will show up and ruin the look and create unnecessary extra coats to build up enough to overcome any dips or waves that are present ok?

As to fillers, they really are not necessary with poly if your applying several coats or more, the material dries hard and after the first coat will not remelt itself so no shrinkage to the extent as a lacquer will occur.

After 3-4 coats you can sand smooth using a cork block and continue building till your happy with the look, re-sand, apply your last coat or two of preferred sheen and call it done. Personally i would invest in a few cans of the spray can fast dry poly for the final coats so as to obtain the smoothest look possible. In fact if it was me and not having any choice, i would do the whole job with such and eliminate the sanding of any brush marks that are common to such methods..

Sincerely,

CHEMMY


Last edited by chemmy; 05-01-2012 at 05:24 AM.
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post #4 of 5 Old 05-02-2012, 01:38 PM Thread Starter
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Originally Posted by cabinetman View Post
You mention that you want a 'piano' finish, but say you used a satin lacquer. Do you want that super high gloss reflective finish, like a piano finish, or just a smooth to the touch finish?

Did you use a grain filler specifically for that purpose, like ones called a paste wood filler, or 'grain filler'? They apply in a consistency of mayonnaise.
.
Thanks for the response - I do only mean a smooth to the touch (and eye) finish. I don't actually want it glossy or *too* reflective, as the speakers are going in a theater room. I found the satin gives a nice initial sheen, although for long term I may actually be after semi, but ultimately that isn't my concern at the moment.

I have tried several methods or grain filling the walnut burl veneer, all methods having unique problems:

Epoxy - this probably worked the best. It gave a smooth finish with good dimensionality, and the lacquer adhered to it well. Curing time/sanding was a pain, and I've heard some people simple never get the epoxy to cure right, whereas other people never have a problem. Finally I have longevity concerns me, as Epoxy isn't meant to be exposed to sunlight and I have heard rumors it breaks down when exposed to UV and forms white particles.

Superglue - hardens and fills well but is splotchy, and almost impossible to sand back to the grain. My last attempt it even left a strange spotty white residue on the veneer.

Grain fillers (colored) - these just kill the dimensionality of the grain. Compared to Epoxy of copious brushed on lacquer, these look flat.

Grain filler (water-based silica, Crystalac) - This is just a pain. I never got it to fill the grain entirely, no matter how many subsequent applications. If I apply it without a sealcoat (zinser dewaxed shellac) it really dulls the veneer. With a sealcoat and I can't effectively sand it back, because I end up sanding into the sealcoat and the finish looks blotchy. I can't just leave it on either, since it isn't entirely clear and has a strange clear-blue tint.

Lacquer - I've also tried using Minwax lacquer and brushing on 7 layers. I waited for the piece to cure (4 weeks) then sanded smooth/rubbed it out. This I liked a lot, but after 4 more weeks some of the burls with deep pits started to have noticable cutback on close inspection. It still feels relatively smooth and looks great from any real distance, but I don't know how much it will continue to cut back, or how a lacquer finish that thick will hold up over the seasons.

So any suggestions would be appreciated. Ideally, if it would work and hold up for 20 or so years, I'd like to slather on 10 or so brushed lacquer layers and sand smooth/rub it out maybe after 8 weeks this time. Problem is I don't know what to expect with that and don't want to spend another year practicing finishes before the piece is done. Would a shellac sealcoat underneath or on top of the finish help? Are epoxies more stable grain fillers than I am giving them credit for? Or maybe there are things I am really just not considering...
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post #5 of 5 Old 05-02-2012, 01:47 PM Thread Starter
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Originally Posted by chemmy View Post
If money is no object, i would use 2 component urethane instead of lacquer. If you don't have 200.00+ then i would use WW conversion varnish, or 3rdly post cat lacquer. If you are not set up to spray these yourself, i would then take them to a cabinet shop or with the 2K, to an automotive shop and get an estimate on having professionally done.

Again, if you can't afford any of these methods or materials and can only do it yourself by brush, i would then recommend the fast dry poly instead of the brushing lacquer. Build with gloss and apply the satin or semigloss as the final coat or two. Poly doesn't remelt like lacquer does so once it's cured hard, what you see is what you get.

One of the most important factors for a glass like level surface is making sure the substrate wood/veneer. is as flat as glass before applying any finish!! If not, any surface anomalies will show up and ruin the look and create unnecessary extra coats to build up enough to overcome any dips or waves that are present ok?

As to fillers, they really are not necessary with poly if your applying several coats or more, the material dries hard and after the first coat will not remelt itself so no shrinkage to the extent as a lacquer will occur.

After 3-4 coats you can sand smooth using a cork block and continue building till your happy with the look, re-sand, apply your last coat or two of preferred sheen and call it done. Personally i would invest in a few cans of the spray can fast dry poly for the final coats so as to obtain the smoothest look possible. In fact if it was me and not having any choice, i would do the whole job with such and eliminate the sanding of any brush marks that are common to such methods..
I'm on the verge of getting a quote on a professional finish, which would be uncharacteristically un-DIY of me

Poly was an option I actually gave up a long time ago. I started testing finishes by comparing poly to lacquer to oil before any concern about grain filling. The minwax gloss poly seemed very dark and undimensional, so I dropped it. If what your saying is correct I sounds like it would solve the grain fill problem - is there any way to apply it that might look better, without darkening or flattening the look of the veneer? Maybe a sealcoat underneath might help? I definitely need to go back and try some options with that now.

As for money - I don't have spray equipment and would like to not invest at the moment, however useful it may be long term. I don't mind relatively small expenditures like doing the last layer with a spray poly or anything like that.

Finally, are there any issues with building up a thick poly coat, maybe cracking due to expansion/contraction over the seasons?

Thanks for your suggestions, they are much appreciated!
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