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Too much!!


daveq
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I think I sprayed a bit too much on the headstock of my limba guitar today B) . I don't have pics but you can see a lumpy surface over what used to be smooth. I'm spraying nitro and haven't run into this problem before. Should I wait 24 hrs, and sand it smooth before continuing or just keep going and deal with it later?

The other issue I'll have is that I used a transparency logo (thanks for the turorial Jehle) on it and I'm not quite over the top of it yet - so if I do sand, it might create an obstacle.

What do you think? Please- if you don't really know - just say so in the reply - I don't want to take any chances at this point. The guitar is comming out absolutely beautiful - I don't know if I'll be able to part with this one now either! Crud! - I mean, - yay - I mean, crud!!! :D

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I usually give a light scuffing before spraying so the next coat sticks better. I've had good results by spraying 2 or 3 coats over a 2 hr period each day until I figure I have enough thickness to begin wetsanding. Make a tiny block sander and work around your logo to get rid of the lumps. If you are spraying the whole thing, logo and all, then your logo area will always be "proud" to the rest of the surface. Tape (blue masking tape) over the logo and shoot until the nitro level reaches that of the logo. Then lightly cut around/ peel off the tape, lightly sand and continue spraying.

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If you are spraying the whole thing, logo and all, then your logo area will always be "proud" to the rest of the surface.

Right, I'm not quite above where the top surface of the transparency film is yet but I do understand that it will continue to bulge out.

So, are you saying that I should sand it before the next coat?

Also, I've been experimenting with some scrap and have found that I can spray more often (more frequently than once every 4 hrs) without seeing any problems such as blushing,... I thought I would see that the lower layers would not be able to release the solvent properly but I just haven't seen any of that yet. On the scrap, I'm spraying about once every hour. Am I just getting lucky, will the problems whow up later this month, is it because the air conditions are just right,...? You mentioned that you spray 2-3 coats per 2 hrs - have you seen any issues doing that?

Thanks for the help,

Dave

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So, are you saying that I should sand it before the next coat?

Its always nice to work with a smooth surface as much as possible. If you keep spraying then your lumps will just get bigger. Yes, I would sand things smooth before continuing.

Have you determined what was causing the lumps in the first place? How long were you waiting between coats? And how much laid down for each coat? Spray a little less and wait a little longer and you can avoid any slumping or other buildup. The way I do it works best for me and I'll bet my curing conditions are quite different than yours. I do all my shooting in the back yard on a calm day with rattle cans.

Also the positioning of the piece you are working on is important. If you are just shooting the face of the headstock then your best results will be to lay the piece flat and level. Laquer is very fluid, too much at once and you will certainly see things go wrong. But otherwise, its more forgiving than stuff like polyurethane. With poly there is a smaller time window for applying the next coat. That is, wait too soon and you might get runs, slumping etc. If you wait too long and shoot when the previous layer has lost its tackiness then it won't bond as well. Thats why they recommend waiting 24 hrs, scuffing and then reshooting.

On a side note, I don't think I'll use poly anymore. I didn't use grain filler on my last guitar and figured on filling the grain with clear poly. I can't tell you how many coats it took to bring everything above the grain and then some for wetsanding. I did this over 6 months ago and now I find that the poly is still settling in and likely shrinking, yes, the grain pattern is starting to show on the surface again. Maybe one day I'll disassemble, scuff and shoot a few more coats. Then its hours of wetsanding all over again. Ya live and ya learn, :D .

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Well, this is strange -

I went to do one more coat and noticed that it was no longer lumpy. I guess it leveled itself out without me needing to do anything about it. It's not really strange I guess since it does self level fairly well but I didn't think it would handle that much of a problem all on it's own.

I'm not new to spraying this stuff but I always seem to run into a new problem every time I finish a piece of wood / guitar. I guess I'll be more careful with the amount of spray - I think part of the problem is that I have had to spray in a swirling wind the past couple of days and it's real hard to tell how much is going on and how evenly it's going on. The weather here has not been kind so far.

Grain filling is not a lot of fun. For the limba guitar - I ended up using CA glue. From what I was told, the only other options were epoxy (messy as all hell), and possibly shellac but I didn't want that much of a color change. The CA glue wasn't exactly a pleasure either. I've never used that much CA before - the fumes are real nasty. Even with a respirator and safety glasses - I had to take a break once in a while to get away from it. My eyes were watering like crazy.

Thanks for the suggestions - I hope I can make it through the rest without a new problem arising but somehow I doubt it. :D

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Dave.

For the headstock, I would leave it alone until you have at least about 8 coats on it to avoid sanding thru your label. Maybe a very light levelling, but keep it very very light, just kissing the tops of the worst high spots until you get a feel for how thick the finish is there. The last thing you want to do is sand down to your label, don't risk it.

I shoot a coat an hour or therabouts. The repurcussion of shooting too many coats too fast won't be blushing, that is a complete other story, but what will happen is if the coats are shot too fast too soon, the finish will NEVER dry out, you will have a semi-soft finish a year or two later down the road...been there...

It'll get hard enough to finish off, but never get to real hard consistancy, you will be able to put a thumbnail into it easily, but I don't think you're into that territory yet. In the worst case, if you shoot too many too soon (but not out of control coats), then you just need to let it hang for a few months before finishing off to avoid pore-settling spots from occuring, something I recommend anyway, I always give my guitars (now) about 2 months of cure before finishing them off. And even that's not really long enough sometimes, I have a few that have shrinkback spots after a year or so.

Another rule I learned the hard way is that the more thinner, the more cure-time before final finish, because the more thinner you use, the more shrinkback your gonna get down the road, so keep your thinner to the most minimal as possible and use as much pure lacquer as you can get away with.

On other forums, I would read where some guys would heat up their lacquer so they could shoot it at 100%, no thinner, and I alway wondered why they would go to so much trouble to do that...I figured it out later on...less shrinkback. B)

That CA might have been a bitch to apply, but c'mon now, after sanding it back level, ain't your starting finish as flat as a pancake and brick hard? :D

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Thanks Drak - I'll definitely store that info in some of the less damaged areas of my brain.

So - you wait 2 months before the final buffing then? Crud. I'm being forced into becomming a patient guy :D . Oh well, it would destroy me to go through all of this and not end up with a real nice finish so wait I will.

As for the CA glue - it was nasty stuff (the fumes) but it had to be better than dealing with the sticky goo of epoxy. The surface was nice and hard after sanding it down level and I was surprised that the color wasn't as dark as I thought it was going to be. When the glue was wet, it looked quite a bit darker than the original but after drying, it was very close to the original color of the wood. Of course the nitro will have it's own way with that but I swear that guitar is looking much better than I ever imagined possible. It's damn sexy to be honest! I just hope I don't have too many more learning experiences on this one.

One more question if you don't mind - when it comes time to buff it out - what have you been using to do this? Do you have one of those buffing machines or do you use something else?

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