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Best clearcoat-finishing methods

Discussion in 'Luthier's Corner' started by Frank Martin, Jun 11, 2005.


  1. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    Hi!

    As we already had a thread about the many ways people apply an oil-finish, I'm interested in how many different methods and what ingredients people here use for clear finishes.

    With my bass project having an ash back, I think I'll have to apply a hardcoat - otherwise, I'd just go danish oil-finish. So I'm curious as to what people here think which is the best method.

    How do you prepare the surface?
    What do you use: polyurethane, nitrocellulose, furniture laquer, etc?
    What are the advantages and disadvantages of the lacquer type you use?
    What is your favourite method of applying?

    Thanks in advance!
     

  2. I use a PPG high solids polyurethane. It's a 2 part catalyst hardened clear. I mix and spray in pint sized runs with a Binks detail touchup gun at anywhere between 15 and 20 lbs.
     
  3. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    Thanks, Hambone.

    Anyone else want to share? I'm curious about the effects on tone, as well.
     
  4. There are a ton of good products out there today, and they seem to be a heck of a lot easier to work with than they used to be, as the manufacturers idiot-proof them for idiots like me.

    A lot of boutique guitar builders and repairmen will not let go of nitrocellulose lacquer. It is pretty easy to use, looks magnificent when done right, and the general consensus (among vintage snobs, anyway) is that nothing sounds as good. Can you or I hear the difference? I doubt it, but it's all in the details, and getting every one right is the path to getting the best instrument you can build. Nitro is delicate, meaning it dings more easily than other finishes. It doesn't age like glass, it ages more like wood, in that it tends to fade in color, yellow, and check. Most of the classic vintage electric instruments were finished this way. It is not environmentally friendly, and in some places you can't use it at all for that reason.

    The urethanes, polys, catalyzed finishes, etc. go on easily, sound fine, age like glass (meaning they take the years well), and they take abuse as if they like it. Removing some of these finishes is unbelievably difficult. They can be remarkably tough. Some of them present greater health risks than other finishes. Protect your lungs! I know guys that had to buy space suits with oxygen pumps to protect thier lungs from some of the hi-tech finishes.

    "Guitar Finishing Step-By-Step" (available from StewMac) has a good discussion of different finishes, but the field changes so quickly that the manuals are at least a little outdated by the time they hit the printer. This manual gives you a great foundation and it is easy to use.

    I live in California, where they regulate just about every human activity. With this in mind I am investigating some of the new water-based finishes. At this time, I don't think they measure up to the more traditional formulas in most areas, but I think they are safer for the shooter, they are less likely to be legislated off the shelf in the immediate future, and they give good results. Check out the local repair shops, or the fine furniture manufacturers or repair shops in your area for tips. Good luck!
     
  5. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    So after two weeks, I'm bumping this back to the top -

    AS THE WOOD ARRIVED TODAY!
    Thanks Larry! :)

    New question:
    How to make the grain pop similar to the naptha method?
    I presume that applying a clear finish will get it a bit closer, but what to do for the fullest effect?

    Thanks in advance
     
  6. There are a lot of effective ways. The colors you want and the wood you have are a few of the variables. One that works well for me is the "stain and sand" method. You apply a stain to your surface, and sand most of it off, and then apply your final stain and clear coats. I've used gray, silver, or blackish stain to start. You won't be able to sand all of it off most woods, and some of it seems to sit in the softer grain. If you use water stain in the damp sanding stage, it doesn't add much work to the process, except the sanding stages take longer. When you put your final color over it, the grain seems to pop out. Bird's eye maple seems to really benefit from this treatment. I believe the PRS Black Cherry finish is done this way.

    I've never tried it on a pure natural finish job, and it might be inappropriate for those projects, depending on the particular piece of wood. Under colors it kills! Practice on scrap!
     
  7. Here's the thing...Do you know why the figure pops when you put naptha on the wood? Knowing this will help tell you how to get it to do it with a finish.

    The surface of the wood as it is now is microscopically rough with deep crevices and fissures and high peaks - to the point that it diffuses the light rays hitting it creating the matte looking top. When you put on the naptha, a clear liquid, it settles between all the peaks and valleys of the surface and fills them up with the clear liquid. The naptha acts like a lens, focusing light down between the fibers of the wood. When the wood fibers are all twisted and curly like well, curly wood is, the light reflects off of them back through the "lens" and we see the deep reflections literally from inside the wood. You've probably seen exactly the same effect if you've ever been out in a boat and looked down in the water to see rays of light shooting down into the depths and shimmering as the ripples and waves distorted the surface. This is just about the same only in this case, there's something for the light to hit and reflect off of - and that's the wood. So what works like this but is permanent enough to be a finish? Regular readers of this forum know where I'm going with this :D Clear penetrating oils will do this quite well and once inbetween the fibers, will harden and stay there. Then you can put a gloss top surface on it and that enhances the effect even further.
     
  8. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    The woods are swamp ash for the back and bubinga pommelé for the top, with a wengé veneer in-between - and adding colour would just ruin the beautiful tint of bubinga (IMO, of course, but since this will be my bass, it counts :smug: )
     
  9. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    Sounds like just what I want! Thanks.
    I really love the look of the freshly waxed oil finish of my Corvette, and I originally wanted to do a Danish-oil finish, but as that would leave the soft ash exposed to dings and such, I have to do a hard finish.

    I'll try to look up these products. Hopefully something like Tru-Oil is available here, as well.
     
  10. krap Frank, I keep forgetting that you are in Hungary man! Home Depot reaches far and wide but I'm betting they aren't there yet. :(

    Here's an angle - Try an international order from Brownells...

    http://www.brownells.com/aspx/NS/store/ProductDetail.aspx?p=4952&title=TRU-OIL+STOCK+FINISH
     
  11. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    Thanks, Allan!

    I'll look into it.
    Unfortunately, I have a big test of five maths subjects coming up on Thursday so now everything is pushed aside till the next week...
     
  12. dooft11

    dooft11 Supporting Member

    Dec 30, 2003
    HongKong
    i just tried, they refuse to ship outside US because the tru-oil is flammable!!!! DaMn.. i cant find it in hongkong neither
     
  13. That's just BS! :mad:

    I'll sit you out in the yard with a bottle of TO and a pack of matches and let you have at it all day long and I bet you couldn't make it smolder much less catch fire. I know all about their idiot restrictions but they'll damn sure fly a bottle to me here in the states so what is the bloomin' problem with a few more hours in the air to get it to you in Europe or SE Asia. And don't let them try that "It's mostly linseed oil and that can spontaneously combust" argument either. TO is so polymerized, by added driers and such, that it gets solid within minutes of hitting air. You can't soak a towel or rag with enough to make it stay wet to support spontaneous combustion - Jeez, there's not enough in a bottle! :rollno:

    Wonder how good the money is in smuggling TO overseas? Slip it in through the the same routes as the heroin and pirate DVD's and we could all make a killing. Whaddya say? Who's with me? :D
     
  14. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    I can already see it...
    The Tru-Oil Mob... :D

    But watch out, they got Al Capone for tax evasion :ninja:

    After a quick googling, it looks like I can't get similar things here... maybe as guns are outlawed here, they think there's no need for gunstock finishes? :ninja:
    I'll ask around a bit more later. I should be studying,,, but somehow it doesn't want to work out with all this heat, and two bass projects :D
     
  15. dooft11

    dooft11 Supporting Member

    Dec 30, 2003
    HongKong
    sure i need some for my warmoth! i will do the job but just dont stuck it inside my ....

    sometimes, the rule is... you know.. :spit:
     
  16. dooft11

    dooft11 Supporting Member

    Dec 30, 2003
    HongKong
    i had a can of tung oil from stewmac.. but they dont carry tru-oil
     
  17. daloop

    daloop

    Mar 4, 2005
  18. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    However, if you add shipping, the difference would not be much, I presume.
    Thanks for the link!