Acoustic Guitar Construction

Tony, I thought you mentioned that in sanding the epoxy filler coats, you sometimes get to bare wood while levelling the filler. I'm anticipating staining the project I'm working on. Does cutting through the epoxy filler imply that the stained wood will also be affected? I imagine that if I cut through an epoxy filler coat down into the wood, I'd also cut down into the wood below the stain. I don't have the woodworking experience to understand if I would be causing myself a problem. Thanks.

Peter,
One of the most important things to get right when finishing is the prep work before you even look at your finishing products. The bigger and harder the sanding block you use to prep the wood, the flatter your surface will be. One reason why we get sand through spots is because the wood below the finish is not as flat as it could have been. That is only one reason of many, but it is an easy one to avoid if you prep correctly. Sanding through the z-poxy is not that bad because my process is to use a diluted mix of epoxy and alcohol to coat the whole instrument before I apply lacquer. If you are staining, that is an entirely different animal and I have no experience with it. What wood are you using and why are you staining? If you sand through the stain, and try to reapply it in the spot you botched, you may end up with a blotchy finish if the staining is uneven. I have stopped sanding after the z-poxy application. I now use a scraper and razor blades to level the z-poxy. I don't sand through very often any more.
Hope something I said was helpful!!

Tony, you've said a bunch, I think inadvertently: don't sand the z-poxy, scrape it. No sanding through. After immensely careful blocksanded surface prep. That might be sufficient.

Applying the stain is related to the species used for back/sides: sycamore. Laminated, too. The vendor I got this project from three years ago commented that there were enough fussy spots in the wood as to warrant a dark, solid finish. Can't see black lacquer, but I can see a dark stain. Can't see the fussy spots, either. Vendor may have been justifying a discount by claiming that the wood was 'seconds' thus allowing the deep discount for some of his inventory while maintaining full pricing for the rest of it, even though the entire inventory was of the same quality.

Dunno, but I don't want a light wood box.

Thanks very much for taking the time to reply. Much appreciated.

It aint no thang.

Great video, You build some awesome guitars!! Love the KOA guitars you did. In your finishing, you go right from zpoxy to the Brushed on Deft laquer, Is a vinyl sealer necessary?? I am starting to finish my first kit I have done three zpoxy sessions, I made the mistake of not going back and hiiting the sand through spots in the zpoxy. I sprayed the Behlens vinyl sealer and found blotchy areas the next morning. So it was back to stripping all the vinyl sealer off tha back and sides , then doing another thin coat of zpoxy. Do you brush laquer directly on your soundboards with no sealers or epoxy filling? I will take your advice and scrape the zpoxy instead of sanding this last coat. Thinking about skipping the behlens laquer system on this one as its to cold to spray outdoors right now. (I don't spray in my shop, I do my spraying outdoors). I May just give the brushing Laquer a try after watching your video. Thanks for any help, Jack.

You will not be disappointed with Deft brushing lacquer. The only trouble I ever had with it was when I applied over some stain (Minwax) that that was not completely dry. The Minwax brushing version I believe is a little harder once completely cured and works just as good -- but has a very strong odor. Not to worry, there are no additives or chemicals in either that that make them inappropiate for use on musical instruments -- I've seen this comment at other sites and it is total BULL S***.

Jackspt28 wrote:Great video, You build some awesome guitars!! Love the KOA guitars you did. In your finishing, you go right from zpoxy to the Brushed on Deft laquer, Is a vinyl sealer necessary?? I am starting to finish my first kit I have done three zpoxy sessions, I made the mistake of not going back and hiiting the sand through spots in the zpoxy. I sprayed the Behlens vinyl sealer and found blotchy areas the next morning. So it was back to stripping all the vinyl sealer off tha back and sides , then doing another thin coat of zpoxy. Do you brush laquer directly on your soundboards with no sealers or epoxy filling? I will take your advice and scrape the zpoxy instead of sanding this last coat. Thinking about skipping the behlens laquer system on this one as its to cold to spray outdoors right now. (I don't spray in my shop, I do my spraying outdoors). I May just give the brushing Laquer a try after watching your video. Thanks for any help, Jack.

Hey Jack,
Thanks for the kind words about my guitars and video! You are obviously a very smart, and handsome man.
I do not seal the sound board with anything. I brush a thinned lacquer onto the whole guitar. I add about 10% thinner to the lacquer. It seems to help with the flow out. Spruce, cedar, or redwood are closed pore woods, so there is no need to pore fill them. For the koa guitars, yes, I did pore fill the sound boards with z-poxy, but Koa is a hardwood with open pores so it is necessary. Also, if I do a hardwood rosette that needs pore filling, I will hit that with z-poxy as well. I take care to remove the z-poxy from the spruce. I have also been known to simply add a few extra coats of lacquer to the rosette to fill the pores. I will drop fill any remaining pores with straight lacquer that has been allowed to thicken by sitting out in a cup for a while so the thinner can gas off.
I do not use a vinyl sealer. Z-poxy is compatible with nitro lacquer, so there are no adhesion issues if you go straight onto the z-poxy with your nitro. Spraying when it is cold is not really an issue as far as I can tell. However, when I have sprayed rattle can lacquer when it is cold, I have gotten blushing issues. The strange thing is, the lacquer blushes on the surface, but not where the braces are glued to the other side of the sound board or back. It is really strange because you can see the lacquer is cloudy but where there is a brace, the lacquer is crystal clear. A quick shot of Behlen's blush remover in a rattle can clears it right up though, so no worries.

The major difference between spraying and brushing is you have a lot more sanding to do to get the finish smooth as glass when you are done. Also, it takes roughly forever to fully dry. I have had a guitar lacquered for two weeks and when I put it on a towel to do the set up, the lacquer will pick up the texture of the towel. The problem seems to be that the lacquer skins over very quickly as the thinner gasses off, and that seals in the thinner from previous coats. To combat this, on the last guitar I finished, after all of the coats were on, each day, sometimes twice a day, I would take my sanding block and some 600 or 800 grit paper and scuff the whole guitar. I was not trying to level the finish at this point, just scuffing the surface so the thinner could gas off. I also put a fan to gently blow on the guitar. I read somewhere that air movement can help to speed up the drying process. It can't hurt, so I do it. Some guys even build special boxes to put the guitar in that circulates the air to prevent the fumes from building up which supposedly slows the drying. I will scuff and blow each day until I can barely smell the lacquer. The fainter the odor, the more dry it is. after 14 days of scuffing, the aroma is pretty faint and I then begin my wet sanding with 1000 grit. After all of the scuffing with 800, the finish is pretty close to level so not much sanding is left to get it level.

If you have any other questions, please feel free to PM me or ask here. I'm glad you found my videos helpful.