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Finish issues! For warning.

Discussion in 'Luthier's Corner' started by thebassbuilder, Apr 19, 2013.

  1. thebassbuilder

    thebassbuilder

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    I just sanded down the final coat of finish last night to 1500on the bass I have been working on and noticed some hair line cracks coming through the finish. Last night they were small and today they have spread all over the knob section of the body and by any drill hole on the bass. This is the second time I have used this finish and both times the same results. The first was on a neck I sprayed and now this body. This time I followed the directions to the "T" and still the same result. I even check with the maker before spraying this body and mentioned the bad results I had from it last time. They told me I sprayed to much finish on it. So why did it happen again? I know now I will never use this stuff again it is the Qualalacq Lacquer Satin by Behlen. The only reason I wanted to use this in the first place was to get a satin finish that I did not have to create by hand. Let me tell you, I do not know why they call this stuff satin when it will buff out to a mirror shine and clear as anything.

    So now I think I am going to spray the thing a solid color this time. Can someone tell me should I take this finish off completely before adding anything else? Also if I want to go with an automotive finish this time can I use a rattle can primer and get good results? Also will the primer cover/seal off any lacqure that may get left behind/missed if I need to fully remove?

    I tell you if I did not have bad luck I would have no luck at all!
  2. na4ito

    na4ito

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    Be sure to remove all the old sh*t.
    Other questions are for the finish manufacturer. Sue them maybe.
  3. Neek

    Neek Supporting Member

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    Were you wet sanding? Water probably leaked into the wood causing it to swell and crack the finish.
  4. thebassbuilder

    thebassbuilder

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    I did wet sand and thought that could be the issue. I wish I had taken some pictures of it. I am not sure this is from wet sanding becasue of the amount of cracks and how far into the body area they go. It looks like a Fender Custom Shop job where you see spider cracks (is that called crazing ?) all over the body. If I was going for that old distressed look I would have nailed it. So maybe I have found a use for this crap after al. If anyone ever wanted a distrested finish that looks like it is about to flake off use this stuff.
  5. Hopkins

    Hopkins Supporting Member

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    By the product description I am guessing thats a pre-cat lacquer, chances are you got the finish to thick. Pre-cats are not good for instrument building because you cant get a thick enough finish to get perfectly level with out it cracking. That stuff is better suited for cabinet doors or table tops. Its not good for instruments.
  6. thebassbuilder

    thebassbuilder

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    Well Great, now you tell me!
  7. Big B.

    Big B.

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    I would agree with this 100%. I work with cabinets daily and pre-cat lacquers are specifically designed to be efficient for production shops by creating an attractive finish in as few coats as possible. I would never spray more than 4 coats of pre-cat cabinet lacquer if possible where I would expect to spray 9-12 coats of lacquer to an instrument before buffing.

    You seem to be comfortable applying a lacquer finish so I would recommend removing the current finish completely and starting over with a nitro cellulose lacquer intended for guitars. The process is pretty much the same and I find nitro lacquer to be even more forgiving than cabinet lacquers. I would personally recommend the Seagrave/Mcfadden products as they work great for me but I suspect any of the popular products will work just as well if used properly.

    Edit: I just looked up qualalacq and it is a nitrocellulose product. While everything said above is true it doesnt seem to apply to your situation. The only time I've had an issue with cracks forming under nitrocellulose was due to small cracks in the wood of the top. Even though the cracks were filled with epoxy or CA glue and were invisible a small hairline crack would appear inside the finish over each one. They were very small and couldnt be felt on the surface. Short of that I dont really know what to tell you. Good luck! :)
  8. joeyl

    joeyl Supporting Member

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    I had cracks in nitro due to water seeping into the neck and pickguard screw holes during wetsanding. It cracked the finish pretty badly in several pieces. Now I either drill after finishing or plug the holes with wax.
  9. Bruce Johnson

    Bruce Johnson

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    I agree that your cracking problem is probably related to excess water getting underneath the paint during the wet sanding, by soaking in through the open holes.

    Try doing your wet sanding with Mineral Oil, instead of water. That's Mineral Oil, which you can buy in the Pharmacy, not Mineral Spirits. You don't use much. I put a little dish of it on the bench, dip my fingertip into it, and wipe a little bit on the sandpaper. Sand away, as long as it feels slippery. Then wipe off the excess. The Mineral Oil does a great job lubricating the sandpaper for very fine grit finish, and it doesn't soak into the finish like water can.

    After you've sanded an area, wipe it down with a 50/50 mix of water and denatured alcohol. That will clean off the mineral oil residue without soaking in.

    I use water-based lacquers and polyurethanes, which are particularly sensitive to water during wet sanding. But the mineral oil trick also works well with other types of finishes.

    Just so you know:
    When you buy a Satin finish, it's intended to be sprayed as a final top coat, with NO sanding or buffing. It has some fine particles mixed in with it which, after spraying, leave a lightly textured top surface. That's what gives it a satin sheen. If you sand it and buff it, it will shine up.

    There are two ways to get a satin finish:
    1.) Build up your coats of clear, level sand them smooth, and spray a final top coat of Satin Clear over it. That's it. No sanding, scuffing or buffing. It's done.

    Or 2.) Build up your coats of clear, level sand them smooth, and then texture the surface yourself, using fine wet sanding, steel wool, Scotchbrite or other techniques. Different techniques will give you different amounts of sheen.

    Don't give up. Painting is the hardest part of building instruments, in my opinion. I've been a pro Luthier for 20 years, and I still spend far more time fussing and fighting with the painting process than with the woodworking, metalworking, pickup winding, etc.
  10. Hopkins

    Hopkins Supporting Member

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    Ahh, I just read the product description, it said its a hard durable finish that is suited for a table top. That sounded more like a pre-cat than a nitro lacquer. Sorry for the misinformation.
  11. Neek

    Neek Supporting Member

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    It is still valuable information to have in the endless search for "the perfect finish"! :)
  12. thebassbuilder

    thebassbuilder

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    Thank you everyone! This is great info and I do agree the finish is one of the hardest parts of building the guitar. Now I get to sand it down and start over, fun. I am thinking of going with an automotive finish on the next go round. What do you use to seal the wood so you can add automotive paint to the body? Also has anyone tried a rattle can of primer and do you think it is of good quality to add a good quality finish?
  13. Hopkins

    Hopkins Supporting Member

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    All of these are automotive finishes. I either use grey lacquer primer, or just a few coats of clear as the sealer. I prefer automotive urethane over nitro because it drys much faster, and is more durable.

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  14. thebassbuilder

    thebassbuilder

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    Cool I was wondering if that is all you use is some clear as a seal coat. Thank you! And great work!
  15. Beej

    Beej

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    Exactly. It's not like automotive finishes are just for automotive purposes. They are basically the most durable and hardy outdoor quality finish you can get, in a complete rainbow...
  16. brstma

    brstma Supporting Member

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    I was talking to a tech at Behlen today who told me the only lacquer product they make that he recommends for a guitar is the Stringed Instrument Lacquer. He told me the Top Coat and Pre Cat products are too hard and will most likely crack, especially if built up too thick or in extreme temperature change. Most of the other lacquers products they make are meant for touch up work and may be too soft to provide good protection.

    What about a rubbing compound? Are there any specifically made to take the gloss out of a lacquer finish? (Like Tru oil has the stock sheen and conditioner to take the gloss out) Behlen has some satin lacquer sprays but he did not recommend them on guitar for the reasons mentioned above. I am hoping to retain some sheen in the finish, not high gloss but not flat either. Right in the middle.

    I am refinishing a bass That I already refinished with Minwax poly. I applied the last coat a month ago and it's just not getting hard. It's soft enough that a light touch with a fingernail leaves visible scratches in the surface. I applied about 5 very thin coats letting each one dry for 3-5 days. I recommend avoiding the Minway poly. Looks great but marks up easily.

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