Official Luthiers Forum!

Hello all, this is my first post!

First of all I must admit that I'm not actually building a lute but a pair of speakers. I've been lurking around this forum for weeks and it is a truly inspiring source of information. Since I'm finishing the speakers more or less the same way as you would a guitar I thought I might try my luck at asking some questions here. I sincerely hope you don't mind! If you don't need the fine details just skip straight to the schedule below.

So far I've spent a fair bit of money and time sourcing every material and tool I need for the job. Even built myself a working spray tent. I have the design I want nearly finalized, and my speaker kit has arrived. The only thing left, is to let you guys check my finishing schedule for any potential problems I might have!

The relevant details:

Inventory: I have a spray gun setup with regulator and filter, grav-fed touch up gun with 1mm tip, Colortone WB lacquer imported from the US, lacquer retarder, Feast & Watson diacetone alchohol-based dyes, American Oak veneer, Timbermate wood fillers. Sandpapers of every other grit from 120 to 1500, then somemore in the micro mesh grits from 3200 to 12000. Random orbital sander (ROS). All the requisite solvents.

Some prior experience with basic woodworking and model making.

Prep: 3 sample boards just to figure out what worked and what didn't. Lots of reading on the net.

The finish: Lacquered oak veneer with a black stained gothic motif, polished to a high gloss. (See attached picture for design)

My schedule:

1. Assemble MDF speaker cabinets.
2. Fill gaps in joins with Selley's plastic bond gap filler. (Seal mdf with poly to protect from WB materials?)
3. Mask off adjacent sides to prevent glue contamination. Iron on veneer. Trim off edges with sharp knife. Leave some overshoot. To simulate end grain, use vertical grain on front, top, back. Horizontal on sides.
4. Hand sand edges down so veneer pieces are flush with each other. (Fillet edges with #240 grit to protect against knocks?)
5. Washcoat with 3 parts water 1 part WB lacquer to raise grain.
6. Apply timbermate filler. Scrape off excess. Hand sand with #240 till clear. Repeat once or twice till surface is smooth.
7. Washcoat with 5 parts water 1 part WB lacquer to seal. Lightly hand sand with #320.
8. Mix teak yellow stain with reducer and apply with disposable cloth.
9. Print and cut out frisket.
10. Apply frisket to entire cabinet. Adjust spray gun to low material and spray black dye. Weather motif with plastic abrasive pad.
11. Mix 2 parts lacquer, 1 part black dye, 1 part teak yellow dye. Set spray gun to minimum material, fan pattern to circular and tone edges. Follow up with 1 part lacquer 1 part black dye and tone outermost edges.
12. Adjust spray gun material to max, pressure at 35psi. Fan pattern at max width.
13. Spray 4-5 coats, 1.5 hours apart each depending on weather.
14. Let dry for a day, then drop fill with superglue and sand with 600 grit paper. Sand with steel wool. Mist evenly with DA. Continue spraying 4 coats a day. Sand with 400-600. Repeat till good thickness achieved.
15. Allow to cure for 2-4 weeks. Dry sand 800 through 1500. Wet sand with micro mesh from 3200 through 12000.
16. Buff with 1 micron polish.
17. Buff with haze remover.
18. Buff with wax.

Questions:

1. On a sample board I did, I strangely sanded through about 12-16 coats of lacquer to bare veneer. I made sure every wet coat I laid on covered the piece entirely, and took care not to go over the edge with my ROS. My guess is the water warped the veneer enough to poke upwards, but I'm not too sure. I used strips of veneer edging the timber shop gave me as a sample for this one.
2. Is it advisable to fillet veneer edges? My speakers are 7kg each and I'm worried the sharp edges can get knocked and crack through the lacquer and veneer. The veneer isn't very thick, about 0.7mm.
3. Do I need to mix the dye with lacquer for toning, or can I just spray on the dye as is? I saw in a youtube tutorial that you mix blonde shellac with dye for toning, and tried (successfuly) to mirror it with WB lacquer on a sample board.
4. Generally how much do you take off a wash coat when sanding before staining?
5. What grade sandpaper/steel wool would you use to subtly cut back a stain?

I sprayed my first neat coat of WB lacquer today on my 3rd sample board. Like the washcoats before, I'm getting small circular spots between 2-5mm in diameter in the coat where the lacquer has dried incredibly fast while the rest of the coat is still wet. When dry the spots are completely imperceptible. What causes this and should I be worried about it?

Is there a reason why nobody is replying? Please tell me if I've done something wrong!

After letting the first day's coats dry on my 3rd sample board the fast-drying spots have now become dimples in the finish. There's no particular pattern to the way the spots appear, they're just generally scattered across the surface. Here's what I did to the board previously:

1. Filled with turps-based grain filler. Sanded with stearate free paper.
2. Filled with Timbermate (water based filler). Sanded with stearate free paper.
3. Stained with spirit-based dye.
4. Lightly scuffed with synthetic abrasive pad.
5. Mixed WB lacquer with spirit-based dye, toned edges.
6. Sprayed 3 medium thickness coats of WB lacquer.

I have a feeling these are repel spots, but I can't find much documentation about it. Can anyone tell me what this is?

Perhaps a general finishing forum would be better for replies.
Guitars tend to be finished in specialised finishes in the main, nitro, special waterbased, french polish etc, so maybe nobody's replying because of they don't have the answers.
Best of luck.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Hey Colin, thanks for your message! Actually the reason I'm posting here is because most of the knowledge I gathered about finishing came from luthiery websites such as this, and especially this site. The lacquer I'm using is Stewmac's Colortone Waterbase Lacquer, which is related to Target Coating's EM6000 and similar to Grafted Coating's KTM-9, all of which I understand are specially formulated for guitar finishing. I've seen Timbermate grain filler mentioned in a luthiery forum (not sure if it's this one), and micro mesh abrasives in quite a few places. The stain I'm using is Feast Watson prooftint, which I've seen mentioned in guitar finishing at least once. For almost all intents and purposes my finishing schedule is no different to how I would finish a guitar based on what I've learned here.

Regardless, I'll keep watching this thread for answers in case anyone has an answer.

In the meantime Victor, check out Target Coatings "forums" .... lots of stuff I'm sure you'll find useful. Can't speak about veneered furniture, But I've used EM6000 & Ultima, and have sprayed both tinted and clear over sprayed dye on bare wood (see recent thread). if I read correctly, I wouldn't use a ROS.

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Dave
Milton, ON

Here's a few "answers" for you



Some people manage to get good results with stain in water directly on wood. For me, that's the quickest way to a disaster finish that I know of. Seal the wood first (I use shellac) then spray on your dyes in some sort of carrier. I've used shellac and Colortone WB with good results in either one. I use the WB Lac. as a carrier now a days as it's easier to clean the gun.



Enough so that it's pretty level, but not so much that you've gone to bare wood in spots.




Never ever ever ever ever use steel wool with WB finishes. You could probably try a fine grade scotch bright pad but I imagine you'll probably have to start over. Next time, use a more dilute dye and more coats to get it dark - much easier to control that way.

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Thanks Dave, I'll check it out. Do you remember why not to use an ROS?



Thanks Andy, can you tell me what the function of the carrier is? My dye is alchohol-based so I'm not expecting any problems with raising grain.



How do you tell what's bare wood and what's not with a thin washcoat? To my inexperienced eyes bare wood and washcoated wood looks virtually the same. I've been playing with the idea of tinting the washcoat just a little bit to help me see it.



Thanks for reminding me about the steel wool! Yes, I'll try diluting the dye more next time if I can make sure the diacetone alchohol isn't what's causing the repel spots.

The "carrier" is the shellac or the lacquer. If you spray dye directly on the sealer, even if it's alcohol based dye on shellac, it's too easy to get runs and spots. If you put it in a carrier, it stays where you spray it (within reason of course- assuming you're not spraying too wet). When I tint, I spray tinted WB lac. on top of a shellac sealer. The shellac seals the grain of the wood so I don't get weird absorption from the grain or any raising of the grain. If your dye won't dissolve in WB, I would recommend spraying about a 1 to 1.5lb cut of shellac with the dye in it.



I admit, it was kind of a wise ass response - I typically will wipe on one or two coats of shellac and not sand back afterward to ensure that I don't burn through. With a 1lb cut of super blond, it's easy to wipe on a thin even coat.

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

My first thought on this would be that Lacquer and Poly do not work together. You mention a poly base coat. then applying lacquer. That is a place of failure from the start. They are not compatible.


Just my quick observation and .02cents worth

MK

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I'm outside looking in, just farther from the window than most.

Hey Mike, the poly is going onto bare mdf to seal it from moisture, then covered in veneer, which is then sprayed with lacquer. The two finishes will never meet. It's an MDF>Poly>Veneer>Lacquer sandwich.



Good point with preventing runs, but what if you're just toning and the dye flashes off immediately (drycoating)?

The only sealing I do is with some diluted WB lacquer. It didn't occur to me to buy a sealer because I've read and been told a few times that plain lacquer can do the job just the same. (Of course I did ignore the other half who say sealers are necessary) At least point buying a sealer's not financially viable - I just had a gallon of lacquer shipped to me and the shipping cost was higher than the cost of the lacquer itself.

My dye emulsifies in WB, at least long enough to spray and flash off.



So, conversely, it's fine if I spray on a cut solution of WB lacquer and then not sand it back before staining? I've always wondered how the effect of staining bare wood compares to staining the finish/sealer.

First time I did a very mild sunburst I sprayed dye in alcohol over a shellac seal coat - I couldn't get it to work. The dyed alcohol beaded up and gave many splotches. I had to sand back and re-did it with dye in shellac over a shellac sealer and it worked perfectly.



Problem is that the WB lacquer will raise the grain when you spray it on and you'll have to sand back. The reason I seal with shellac is that it doesn't raise the grain and is totally compatible with the target USL. Thusly, I seal without having to sand afterward. Actually, I'll usually wipe on a coat or two, sand back and do one final coat or two without sanding.

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Ok, I'll remember that.



One of my early steps in the process was to washcoat the veneer before applying grain filler. My theory was that the water would raise the grain and the relatively high solids content of the washcoat would "lock in" the grain. Barring this I thought that once grain was raised with water it would stay that way without returning to its original arrangement.

After applying filler I sanded the first washcoat down with the filler, then applied another washcoat before dyeing. I'm not sure how effective this is but I am seeing a lot less grain after the first day than I did when I was testing my second sample board.