Shellac finish on cherry veneer

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I've been refinishing a loudspeaker I built several years ago that was veneered in american cherry with the corners made of solid brazillian cherry (different species). Due to cherrys tendency to blotch, I used a red/brown alcohol-based dye mixed into shellac and sprayed it on. To minimize splotching, I sprayed on a light 1.5# cut of shellac. The color came out very nice, however the cherry still splotched. On the other hand, it could also be due to ray flecks in the wood. Having learned much about using shellac a few years ago on some custom wood boxes, I decided to build a film on top of the existing finish, then flatten it to remove defects and polish it to a smooth, soft glow. Well, that was the plan anyway. . . . Removing one of the tweeters caused a small piece of the veneer to separate and crack. Now this repair was added to the list. Next, it quickly became clear that while I had sanded the veneer smooth, I didn't flatten it. As such, every time I cut back the finish, I ran into problems sanding through the original finish right down into wood. I would fix these areas with dye and a fine brush, recoat and run right back into the same problem. The final straw came when I sanded one panel up through 1500g with sandpaper, 2500g with syn. steel wool and polished with Meguiar's #7 polish (which I later discovered has no grit at all). It looked awful in harsh, raking light: uneven, ripples, scratches, etc. A far cry from what I was expecting. Frustrated, I decided to remove the finish, flatten the veneer, then rebuild the film, flatten the finish, then polish. In other words, start over from scratch.... While listening to football on the radio, I started yesterday pulling the finish off, then flattening the veneer. The difference between just sanding something smooth and flattening it is that a rigid block is used to back the sandpaper in the later (the larger the better) while the former is done by hand or machine. The distinction being that just because a surface is smooth doesn't mean it's flat and smooth. Building a film finish requires both. I originally chose shellac because it dries very fast compared to oil-based finishes and when I was applying the finish, it was quite hot and humid here in Tx. Oil would take days to dry and weeks to cure. Multiple coats of shellac can be applied in a single day. I also hadn't used it before and wanted to learn to apply it. In addition, shellac is an excellent vapor barrier, easily repaired, can be padded on and moved around to level it and completely removed with denatured alcohol when necessary. This is due to it being an evaporative as opposed to curing finish. It doesn't polymerize and cross-link like polyurethane does. Finally, it can be wet-sanded with mineral spirits or even non-curing oil to achieve a smooth finish, and greatly reduce sanding dust without either affecting the curing of the shellac. Here's what it looks like. Very nice deep red/brown color. The darker areas are 'splotches' where the grain density is lower thus absorbing more dye. The thin shellac wash coat was supposed to prevent this, but no joy. In flat light, it looks beautiful. However, in raking light you can see brush marks and other defects. It also looks insanely glossy. (I wish the sled looked this glossy!) With the work light showing, brush marks reveal themselves: To remove it, I lay down some alcohol, then scrub it off with SSW (syn. steel wool). Here's what it looks like after the first pull: The dull areas are the surface of the wood. The shiny, streaky areas are partially dissolved shellac still on the surface. Here I've removed the rest of the finish, then begun sanding with 220x stearated sandpaper glued to a 5" x 9" block of flat wood. The blonde areas were all high. As they are flattened, the darker areas will become lightened as well as the entire surface becomes more uniform. After considerably more block-sanding, the surface is nice and flat and very smooth. The darkened areas have lightened considerably. Note that it's impossible to get it all blonde again as the dye has penetrated deep into the softer areas and won't come out. There is a single, thin vertical line running from top to bottom. That is a veneer seam and a low spot. I'll fill that in with shellac until it's level with the surrounding surface, then flatten it. Here's a close-up: I'll post more as work progresses along with some tips I've learned about working with shellac. For reference I use Bob Flexner's excellent book "Understanding Wood Finishing."
 
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Alot of work really should be looking into polyester wood finishes would make your life alot easier could be done in 2 or 3 coats. Dye should be applied by spray only or you will run into problems.
 

sleddriver

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I don't agree...at all. Your comment doesn't even make sense to me. Polyester to me = gelcoat. Been there. Done that. Owned two sailboats and did my own gelcoat work plus polyester resin + mat. Shellac is MUCH easier...and less expensive. Not all dyes have to be sprayed either. As previously stated, alcohol dyes can be used to tint shellac, which can then be brushed/padded/sprayed on. Where do you get your information? Obviously not from Flexner's book. Finally, the finish wasn't the problem. It was the uneven veneer underneath. Nothing will fix that except leveling it with sandpaper. I forgot that step when I built them 13 yrs ago. As with most painting and finishing, 85% of the work is surface prep. Laying down a coating after that is a piece of cake!
 

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Update I: Spent some time this evening sanding down both the front and top of each cabinet. Now they're very smooth and flat. I'll need to turn some dowels to plug the socket holes. They're far too large for such a narrow front. I also broke a hardened screw in half. See top woofer screw hole. There's about 1/16" sticking out! Wow...and I pre-drill all holes too. I'll be sure to lube all screws this time upon reinstallation.
 

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Update II: I've now completely flattened all the dyed surfaces, scrubbed the remaining stain 'laterals' on sides & top with sandpaper, SSW (syn. steel wool) and alcohol. A fellow WW'r suggested that when I sprayed the dye/shellac on, the round pattern of the sprayer left long horizontal lines, and after thinking about it, reading some more, and watching numerous finish spraying videos, realized he was right. The pro's only use spray guns with a "fan" pattern, as it ensures the most even coverage. Makes sense. Now that I've suffered that mistake, I won't repeat it again. You gotta love stereated sandpaper: Very tough to clog. I've been dry sanding more as it's easier to see what I'm doing as opposed to wet sanding. But dry sanding with regular wet/dry or garnet paper, is frustrating (especially with shellac) as it'll quickly clog & corn, which can wreck your work. Last night, I laid down a coat of the Behlen Solar-Lux stain, which is a beautiful deep, red/brown color. Then I padded over it with very thin shellac to even out the color. Today I applied more and dyed the other cabinet. They both look very dull, which is normal with dye. I was able to match the color & tone left on the edges quite well. Once a few coats of shellac are laid down on this, the color will really pop and it'll look 6" deep. Notice I removed the ugly, black grille sockets. They were just too large for such a small panel. I'll trim a dowel to fit, glue it in, then stain to match. I never use the grilles anyway: They cause +- 2dB ripples in the tweeter response above 8kHz or so due to the frame dimensions becoming very close to the wavelength. One more tweak: Smoothly contour the rear port "drain" to ease the abrupt transition. I'll also have to add some caulk to seal the joint around the straw-filled port tube to prevent air leaks. I also plan on substituting larger inner diameter "frozen margarita" straws for the much narrower standard types. The rationale here is to minimize port turbulence and increase laminar air flow. Further, it makes port tuning much easier. It does increase the resistance on the mid-woofer's motor, so you can't get always get away with this trick. I'll verify system resonance and port length after reassembly.
 

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Thanks! Never intended the refinish to last THIS long! Royal PITA because my skills have greatly increased since originally building these so long ago. This was my first veneered, furniture-level work and the first time I'd ever used dye & shellac. I didn't realize the importance of FLATTENING the wood...not just SANDING it smooth at the time. C'est la vie..... Time for beers and black-bean nachos Cheers2
 

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Update: Today I worked on filling the holes left over from the grille sockets. I had some hard-wood dowel that was 0.60" and using the Taig lathe, turned it down to 0.585" for a tight fit with no glue. Blue tape protects the veneer from possible scratches from the saw, which has teeth with no set on one side making flush-cuts possible. I used a small pocket plane and sandpaper on a small block to level the surface: This will be the last time I use these on a veneered front. I've applied several coats of 3# cut shellac on the sides and top, leaving just the fronts. Overall, it looks very good but a bit darker than expected. As such, I'm not tinting the shellac. Looking forward to being done with this project! It's already past the middle of Oct! Stay tuned.....
 

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Update: With the plugs installed and sanded flush, now the trick is to dye the raw wood to a close match. I used a 50% dilution ofo the dye to start so it wouldn't be too dark. With each application, the wood darkens. After touching up all eight, this is how it appears: You can see some 'dark/dusty/smuggy' areas...this is due to grain density differences and results in cherry's reputation to 'splotch'. It is tough to avoid. This dye presumably has no pigment in it at all. However, in areas where it is quickly absorbed compared to others where absorbtion isn't so quick, it turns dark due to the black in it. That's why you see it like this. It'll be a bit less noticeable under shellac as I can tone it a bit before brushing it on.
 

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Update: Well I've hit a major snag and seem unable to extracate myself from it. Thousands upon thousands of tiny pinholes/craters invade each new coat I apply or the shellac refuses to flow into the previous layers craters, thus they remain. While the other areas build up, these refuse to. Very, very odd. Major PITA...never run into this before. I had hoped to be long done with this project by now. Emphasis on long...I've been trying to figure this out for over a week. No joy.
 
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Without pics it's hard to tell what u have might want to look into a product BYK 320.
 

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Well after consulting with an expert finisher, he suggested that I'm not only putting it on too thick, but that I'm putting on too many coats...that are too thick, compounding the problem. I was waiting about thirty minutes between coats, then sanding. He said if you put on say three coats, it takes coat 2 longer to dry than coat 3 because shellac is an evaporative finish and the solvent (alcohol) partially dissolves the finish layer beneath it, so that layer becomes partially redissolved with a new wet layer sitting on top of it. And now both have to thoroughly dry before a new coat is added on top. So I'm trying to do too much, too soon and making it worse by applying it too thick each time. Doing "too" many things "too" fast and wrong. He finishes everything by spraying pre-catalized lacquer. Unfortunately, I'm not set up for that.
 

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Update: Turns out the brush I was using was causing the majority of the pinholes (which were actually tiny air bubbles) and ridges because it wasn't capable of holding enough shellac in reservoir. When brushing 3# cut, this didn't appear, but with 2# which is noticeably thinner, it does. Being a fast-setting evaporative alcohol-based finish, it almost cures too fast for these brush marks and tiny bubbles to flatten out. PolyU and oil doesn't have this problem, but takes much longer to cure, i.e. polymerize. I'd been reading up on "padding" shellac which is a method of applying it with a pad. Not quite the same as french polishing, but close. To prevent the pad from sticking, a drop of mineral oil is used each time shellac is "padded" on. Further the finish can be refined (literally pushed around) by only using alcohol and oil. Sounds odd...and it is. However, it works...and works well. Plus it leaves no brush marks nor bubbles when using even 1# shellac. The disadvantage is time: It takes far longer to build up a suitable, even film this way than with a brush. I decided on a combination. I would apply a few coats with a brush and when dried, cut them back with sandpaper until all the defects were removed (brush marks, pinholes, etc.), then brush on two more thin coats. After these dried, I would 'refine' the surface using only alcohol and oil. This would remove the above defects and give me an opportunity to experiement with "padding" it on. The alcohol evaporating through the oil leaves a bit of a comet tail as you swirl the pad on the surface. When you no longer see this, it means you need more alcohol. Strong, raking light is a necessity. When this had dried, I removed the oil with paint thinner as I didn't have any naptha on hand. Then I wet sanded with 600g wet/dry lubricated with paint thinner. This prevent the sandpaper from clogging with shellac (called corning)which can damage the fine finish. I wiped off the shellac dust/thinner combination and moved onto the next step wet sanding with 800g. This left an incredibly smooth, very flat satin finish with no defects. In the past, I've wet-sanded up through 1500g, then polished using a car compound, but this time I wanted to see what it would look like by going straight to a compound after 800g. First, I applied some Meguiar's #7 show car glaze, which is silicone-free and contains oil. I'm not sure what level of "grit" is in it. Here's the effect: The first photo was taken from the upper, right hand corner of this one. The M#7 was applied by hand to the lower, left corner. The oil definitely helped to "gloss it up", but did little to polish out the minute scratches in the flat finish. One the bottom right notice how shiny and clear that area is. Here I applied Meg's Ultimate compound by hand using a small cotton pad. This did a great job of polishing out most of the fine scratches, producing a gloss finish. This is what I'm looking for. Here's another angle of the same lower right hand corner. Just to the left, in the middle, is an area only wet sanded to 800g. So the UC took it from that to the right hand corner, in one step. Talk about saving time! (The scratch swirl mark shown is due to using a u-fiber cloth that obviously contained sanding grit). So my "finishing the finish" process is to wet-sand with 600 & 800g, wipe off the slurry, then apply UC and #7 on top. My goal here is not to obtain a perfectly glossy finish sans scratches. That's exceedingly difficult on a wood finish. Plus shellac is rather soft and waxed shellac even more so. What I'm after is the warm, soft, elegant glow from a hand-polished finish that is incredibly smooth to touch. I've been at this project since mid-August! It turned into a black hole. I never expected to encounter so many problems. But perserverence paid off and the next time it won't be so time-consuming....or frustrating. My reference here has been Bob Flexner's Understanding Wood Finishing. Be sure and get the latest edition as the photos are all printed on glossy paper. I'll follow up when it's all done.
 

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Update: Here's a few photos of the finished "finish". I used an ad piece to highlight the polish. I can nearly read the reflected small print! It's tough to get a good photo of it as it looks much better naked-eye. I didn't expect results this good! Flexner does use and recommend car compounds and polishes and polishers in his wood finishing book though and the results speak for themselves. I used Meguiar's Ultimate Compound here + #7 as I had it on hand from earlier polishing out the sled. I used a SurBuff micro-fiber hook-&-loop pad attached to my 6" RO sander along with UC to save time on the large panels. It worked very well indeed. Further, waxed shellac is even softer than de-waxed and both are much, much, softer than auto paint. I used a small cotton make-up pad + UC to work the smaller areas around the driver cut-outs and applied quite a bit of pressure. Still no marring. Given this, I don't see how you could ever damage auto paint with it as it's so much harder. Next time you need to remove scratches from furniture, try UC on a hidden spot to see if it'll work.
 

sleddriver

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Thanks! Steep learning curve. Shellac has many advantages, but also has its quirks. It's not at all like working with Polyurethane, varnish, oil, latex, enamel. It's a whole different animal. The results are well worth it though as the surface is incredibly smooth to the touch and very warm.
 
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