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| Author: | Tai Fu [ Sat Dec 20, 2008 7:17 pm ] |
| Post subject: | how much is enough? |
I have begun putting finish on my guitar and now I have put about 6 coats of clear on it, I did not use a sealer just clear lacquer (I don't want sanding sealer clouding stuff up... I wanted maximum chatoyance or whatever they called it) and I think I got enough to where I can just wait then sand and buff them, or do you think I should put some more coats on? The coats were fairly heavy because I used a spray gun for them.... |
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| Author: | Kent Chasson [ Sat Dec 20, 2008 9:13 pm ] |
| Post subject: | Re: how much is enough? |
FYI, the purpose of sealer is better lacquer adhesion. It sticks to raw wood better than lacquer does. As for how many coats, it's impossible to say. Have you sanded everything flat at least once between coats? The thickness you want is essentially the minimum it takes to sand and buff out without going through (ideally leaving a film of about .003" - .005" on the top). But how much you start with depends on how much you need to sand. Should be plenty in the archives to read up on. |
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| Author: | Hesh [ Sun Dec 21, 2008 8:19 am ] |
| Post subject: | Re: how much is enough? |
What Kent said and if you download Stew-Mac's free-for-download PDF file of dreadnought guitar kit instructions there is a nitro finishing schedule in there that I have used with good results. They have you spraying 9 - 12 coats and again as Kent said the leveling is very important. Much of the early coats are actually sanded off to level the surface. |
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| Author: | Tai Fu [ Sun Dec 21, 2008 9:40 am ] |
| Post subject: | Re: how much is enough? |
The first few coats I leveled between coats because it was quite rough. I thin the lacquer by about 50% because it came in quite thick. I don't know where to get vinyl sealer because I am in Taiwan and they can't ship finishing products overseas. |
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| Author: | Rod True [ Sun Dec 21, 2008 1:03 pm ] |
| Post subject: | Re: how much is enough? |
Tai Fu, thinning the lacquer to 50% is not a good idea. As Todd said 25% max should be the most you thin it. I usually only thin to 10% but I have used it right out of the can with no thinning at all. Thinned at 50% you don't have enough solids left to make a thick coat at all. You'd need about 15-20 coats thinned at 50% to make an acceptable thickness to level and buff. Get some shellac and use that for the sealer, forget the "lacquer specific" sanding sealer, shellac works very well as a sealer. |
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| Author: | Howard Klepper [ Sun Dec 21, 2008 2:00 pm ] |
| Post subject: | Re: how much is enough? |
Kent Chasson wrote: FYI, the purpose of sealer is better lacquer adhesion. It sticks to raw wood better than lacquer does. No! Popular misconception. Sanding sealer actually sticks less well than plain lacquer, because of the mineral soaps added to it to make it sand better. The key word is 'sanding,' not 'sealer.' It's purpose is to make sanding back of your first coat easier, which you might want to do because you need to set up the loose fibers and then sand them off. But there are other ways of doing that, which avoid the sanding sealer's lower clarity and worse adhesion (which is highly unlikely to actually create a problem). I prefer to use a thin coat of shellac and sand that back. Vinyl sealer is lacquer with vinyl added instead of soap. The vinyl does not improve adhesion to the wood; it's there for the same reason as the soap--it makes the lacquer sand better. The reason to use it is that ordinary sanding sealer does not flex as well as musical instrument lacquer (which is more plasticised than ordinary funiture lacquer). It also has the issue of worse adhesion to the top coats because of the soap additives, which isn't a problem on furniture, but can be on more flexible surfaces. It's that flexing that can cause delamination when ordinary sanding sealer is used on an acoustic instrument. Where the manufacturers tell you you must use vinyl sealer with instrument lacquer, they are being a bit misleading. They should say IF you use a sealer, make it vinyl. As to how many coats, people's coats vary by a factor of about 2. So it becomes speculation about how you spray. |
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| Author: | elysne [ Sun Dec 21, 2008 3:41 pm ] |
| Post subject: | Re: how much is enough? |
I've used sanding sealer once and will never used it again. Like you I apply lacquer direct to the wood. I lay one two heavy coats... and sand flat... then 5 coats... and sand flat... and then 2 thin coats. |
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| Author: | Tai Fu [ Sun Dec 21, 2008 9:20 pm ] |
| Post subject: | Re: how much is enough? |
Rod True wrote: Tai Fu, thinning the lacquer to 50% is not a good idea. As Todd said 25% max should be the most you thin it. I usually only thin to 10% but I have used it right out of the can with no thinning at all. Thinned at 50% you don't have enough solids left to make a thick coat at all. You'd need about 15-20 coats thinned at 50% to make an acceptable thickness to level and buff. Get some shellac and use that for the sealer, forget the "lacquer specific" sanding sealer, shellac works very well as a sealer. The reason I thin it so much is because the lacquer I use, out of the can it is VERY thick, in fact it's too thick to be sprayed (it has the consistency of cold syrup). So the only way I can get it to spray is to thin it to the consistency of skim milk so it can atomize properly, in fact the lacquer has quite a bit of solid in it. Now McFaddens which most of you guys use (or Deft or whatever) is thin enough in the can that it can be used in the gun. I used to use another brand that was thin enough to spray out of the can but I stopped using it once I found my current brand because It doesn't dry hard (it's acrylic lacquer) and it's got too little solids in it. I think in the past I had been spraying about 6 coats after color (when doing electrics) and I found that the coats seems to be too thick and it was starting to affect the color so I toyed with the idea of using half as much coat and be more careful sanding... |
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| Author: | bluescreek [ Sun Dec 21, 2008 9:39 pm ] |
| Post subject: | Re: how much is enough? |
I use the finish schedule that martin uses . Vinyl sealer fill seal then apply lacquer 8 coats 1 coat per hour. Let set about 3 weeks then level sand apply 3 coats of finish and then level sand and buff and polish. You want to leave about .006 to .008 of finish on the guitar. On electrics I do apply a little more. I have use shellac and thinned lacquer though I have to admit the mohawk products are a great line. My finishing has stepped up a bit with their stuff. Finishing a guitar is a process and once you find one that works for you , settle on it. Finish is one of the hardest things to learn on a guitar. I cannot stress enough that if you cut corners on prepping you may as well use a roller. poor prep will get you a poor finish. I spend as much , if not more time on finishing than I do building. john |
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| Author: | Andy Birko [ Tue Dec 23, 2008 10:18 am ] |
| Post subject: | Re: how much is enough? |
bluescreek wrote: Let set about 3 weeks then level sand Question, why wait the 3 weeks before level sanding? Is this a shrinkage issue? I would think that it would be a quicker level sand with the finish still somewhat soft. Or does the finish clog up the paper too fast? Do you need the harder surface to level better? |
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| Author: | Hesh [ Tue Dec 23, 2008 10:27 am ] |
| Post subject: | Re: how much is enough? |
Andy I have waited 2 weeks with nitro and 4 weeks with nitro and it is much easier to sand it out with less risk of sanding through after 4 weeks. You are correct too that after only 2 weeks paper clogging was an issue. After I learned this I also learned to place the curing guitar where I won't see it for a month either to avoid any temptation to get impatient. Also, the curing finish is out gassing solvents so it's also a good idea to let it cure where people and pets are not present and probably nothing that could spark either. |
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| Author: | Howard Klepper [ Tue Dec 23, 2008 12:58 pm ] |
| Post subject: | Re: how much is enough? |
bluescreek wrote: I use the finish schedule that martin uses . Vinyl sealer fill seal then apply lacquer 8 coats 1 coat per hour. Let set about 3 weeks then level sand apply 3 coats of finish and then level sand and buff and polish. You want to leave about .006 to .008 of finish on the guitar. On electrics I do apply a little more. I have use shellac and thinned lacquer though I have to admit the mohawk products are a great line. My finishing has stepped up a bit with their stuff. Finishing a guitar is a process and once you find one that works for you , settle on it. Finish is one of the hardest things to learn on a guitar. I cannot stress enough that if you cut corners on prepping you may as well use a roller. poor prep will get you a poor finish. I spend as much , if not more time on finishing than I do building. john You sure that's what Martin does? What's strange about it is not waiting for the lacquer to cure after shooting the final three coats. They will soften everything, and even if they didn't, those three coats are the lacquer that is getting polished, so you are pretty much defeating the purpose of waiting three weeks. I level sand after a few days, shoot the topcoats, then wait at least three, preferably four weeks to polish out. |
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