Official Luthiers Forum!

Hey,

I got myself a kit SG as a starting point in to building guitars, and I'm learning heaps and having a lot of fun. I'm at a point now, though, where I'm second guessing myself about how I've been finishing it, because it's not going exactly how I expected.

I sprayed a few coats of water based spraying lacquer from stewmac, mixed with a combination of cherry and mahogany red ColorTone. The spray job is a bit rubbish, but that's more down to me learning how to use the equipment I think!

Anyway, since then I have got a better idea of my equipment and sprayed around 7 coats of clear lacquer, thinned in a 2-to-1 ratio with water. Those coats total a bit under 2 cups of the lacquer/water solution. I expected by now it would be starting to build up a bit of a shell of clear lacquer, but it just isn't. It goes on looking nice and wet, but when it dries it is so thin it's like I never sprayed it. I find myself getting impatient and spraying too much to try and thicken it up, resulting in runs. I sand those out with a quick wet sand and I'm seeing the red finish on my sandpaper.

I'm not sure why my lacquer coats are drying so thin. I'm wondering if the 2-to-1 mixture of lacquer and water, respectively, might be too thin? It doesn't seem too thin, and I feel like my gun wouldn't like it much thicker, but I'm a first timer so what do I know. Maybe I screwed something up in prep and now the wood is just soaking up all the lacquer? Or maybe this is normal and it's my expectations that were wrong?

I just thought after so many coats the guitar would have that shiny finish ready to be wet sanded and buffed, but it just isn't happening. Does anyone have any pearls of wisdom they might like to share? I'd be hugely appreciative.

Cheers,
Simon

After 7 coats it should be building up. Try spraying with less or even no water. The goal is to use as little thinner as possible. You might also place the body in a horizontal position to lessen the chance for runs. But spraying with less thinner will greatly reduce the problems with runs.

What are you using for a gun, nozzle, air pressure and pattern? You need to experiment with your gun to really get to know it. I always start by spraying on to a piece of cardboard to check pattern, flow and make any adjustments. I have sprayed the old StewMac water based but haven't tried the new stuff. Instead I use KTM-9, however the procedure should be very similar.

1 - First couple of coats are diluted with a small amount of denatured alcohol, these are mostly to seal the wood and any stains or pore fillers (you could also use shellac). By small amount, it might 4:1 or less. Very lightly sand, these coats will almost disappear.

2 - I then spray three coats a day, undiluted, about 1 hour apart. When done I clean the gun with soapy water, rinse, then pour some DA in the cup and shoot it into a rag. The DA cleans all the water out of the gun. I leave some in the cup.

3 - Next day I scuff it with 320 or so, level any runs or dust, drop fill if needed. I then shoot a mist coat of the DA, dump the gun, pour my KTM in and shoot the first coat. The mist coat seems to tack the surface slightly and helps the new lacquer to burn in (since I have been doing this I have had no witness lines). The very small amount of DA in the cup probably dilutes the lacquer slightly, but basically if the temps are right I'm shooting full strength

4 - Depending on the wood and finish I'll usually go for 7 or 8 days - that will be 20 plus coats. Cure for 30 days, wet sand and polish as usual.

Here is a Lester that was done that way - the burst uses SM Color tone dye. Finishing starts on page 8

http://acapella.harmony-central.com/sho ... Paul/page8

I'll add that porus wood like mahogany, rosewood or koa must be pore filled first or you will need to apply many more coats before you start getting a level surface. If you go to the resonator sub forum there are some pictures of a koa tricone (thats the thread title) that was pore filled with zpoxy, then 24 or so coats of KTM-9. Maple does not seem to need pore filling.

Thanks for the replies.


Gun is similar to this one (actually, mine is almost identical to the one in the thread you linked to), 1mm tip, I lowered the air pressure quite a lot after the mess the colour coats caused, and I've opened the spray pattern right up.

The colour coats came out very spotty, and I had to spray from a long way away to stop it running as soon as it hit the guitar. The way it is set up now I'm able to spray the clear from 6"-8" away without getting those runs, getting an even spread of lacquer, and without the lacquer drying before it hits the guitar. But I imagine that is dependant on the consistency of the mixture I was using, so if I switch to a thicker mix I'll need to adjust it. That's not a problem, though.

Could the (in)frequency of my spraying be an issue? I tend to do a coat when I have time, which ends up being 1 a day, maybe 1 every 2-3 days if I'm busy.

Anyway, seems pretty clear that I'm using too much water to dilute the lacquer. I'll do some tests either tonight or tomorrow with straight lacquer to see if the gun can handle it, and make any adjustments as required.

Thanks again to both of you for your replies. If you have any more insight I'd be more than happy to hear it.

Cheers,
Simon

I have always heard that going too long between coats with water based is a problem - unlike nitro it does not tend to melt the previous coats. Since I have been doing the mist coat with alcohol that doesn't seem to be a problem, but I did get some witness lines previously when I would sand thru a layer.

The other thing you might do is pose your questions in the electric guitar sub forum and maybe read the Finishing sub forum at MIMF.

http://www.mimf.com/phpbb/viewforum.php ... b4c509997e

Granted, you are talking about a kit, but the subject is much more general. Good luck

I've sprayed Target USL (which was private branded for stewmac) & now EM6000, basically using Gerald Sheppards schedule of 3-4 coats a day, 1hr apart, every 3 days & have never found a need to thin the finish. Even full strength, deposition is pretty light ...takes me about 20 coats to end up at 4-5mils pre-leveling. All the problems you describe (deposition, runs, blotchy) seem to me characteristic of too watery finish. IMO

_________________
Dave
Milton, ON

Dave - what is the purpose of waiting 3 days between shooting sessions? Has Gerald's schedule been published somewhere? If so, would be great if you could point me to it. Thanks!

Charlie, I feel it works as a partial cure, if leveling between coats or just letting the finish stabilize before piling too much on. Actually I called him, many years ago, when I was contemplating USL & he was very helpfull & his work speaks for itself. I've had no complaint with his advise and, as they say, if it ain't broke.... (I've got enough to worry about).
He posted a summary of his approach.
viewtopic.php?f=10101&t=21823

_________________
Dave
Milton, ON

Thanks guys, appreciate all your comments. Apologies if this was in the wrong spot, I know it's quite a long bow to draw from kits, but I couldn't see a more appropriate spot off hand.

I tried spraying straight lacquer this morning, but it was just too thick. The gun wasn't happy with it at all. Even after cranking the air pressure and making the spray pattern as narrow as I could, I still had to hold the gun still and very close to my scrap wood before it started to coat properly. I've since mixed a 8:1 jar and sprayed a test on some scrap, and it was flowing heaps better.

I'm thinking it's just too cold here at this time of year for the straight lacquer. It's midday at the moment and it's only around 12 degrees celsius (53.6 fahrenheit), and probably colder in my shed! I know that's not ideal for spraying, but I'm an amateur and don't have access to a climate controlled facility.

I'm waiting for my test piece to dry before deciding if the mixture is right to continue with a coat on the guitar. Fingers are crossed.

Cheers again,
Simon

Thanks very much for the info and the link, Dave!! I read through Gerald's schedule and it sounds good. It does seem to make sense with a water borne like 6000 to give it a chance to cure and stabilize a bit before it gets too thick.

This may be a silly question but I don't want to falsely assume it's not significant...in Gerald's description of spray session #2, quoted below, he sprays 3 - 5 coast, waits 3 days and then sands. He then says again that he waits 3 days for the finish to cure. Am I correct in assuming that second 3 day wait period is a typo, and that he actually goes ahead and sprays more coats after sanding rather than waiting 3 more days?

I missed that.......yeah, that must be a typo. No need to wait after sanding IMO.

_________________
Dave
Milton, ON

Thanks Dave.