Blushing or something else???

Discussion in 'Luthier's Corner' started by Jure, Sep 19, 2017.

  1. Jure

    Jure Member

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    A couple of days ago all was fine, guitar was drying and was getting ready for final wet sanding and polishing. When I sanded to 1500 I started to notice some strange things in the lacquer but I thought they will disappear when I polish it. Well, they didn’t. There is something in lacquer visible only if you look very closely and at an angle. On the picture it appears whiter than it real is. In reality it is not milky white. It is like somebody spilled something on guitar and this is the residue but it is inside the lacquer. This is mainly on the top and a little bit on headstock. Back is OK.
    This was my finishing schedule:
    Yellow water base stain followed by shellac a couple of days later. Nitro Clear coat, burst coat and than several clear coats. Two weeks later I sanded everything with 400 and then a final thin clear coat to melt those scratches. There was no visible blushing during finishing. Any thoughts what this is? Please don’t tell me it’s blushing.:Ohno::Ohno:

    [​IMG]
     
  2. ARandall

    ARandall Senior Member

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    When you 400-grit sanded the top, did you get rid of all lowspots??
     
  3. Jure

    Jure Member

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    Thank you ARandall. Yes, all the low shining spots were gone. Would it be possible that last coat did't melt the scratches from 400 grit paper. I was just looking at this through magnifying glass and it seem there are scratches inside. Or is it just my imagination trying to find an explanaton.:hmm:
     
  4. jkes01

    jkes01 Senior Member

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    That looks like you sanded through layers. Wet the area, is the cloudiness still there?
     
  5. Jure

    Jure Member

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    Maybe a little difference but it is hard to say. You are right it looks like it has been sanded through layers, but this is nitrocellulose finish where there are no layers between coats. At least as I understand.
     
  6. jkes01

    jkes01 Senior Member

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    It definitely doesn't look like the layers are melted together. Maybe let us know what product you are using. If lacquer, it should melt and be re-melted with a another coat, but I'd be worried about the cloudiness still showing with just clear.
     
  7. Jure

    Jure Member

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    Thanks jkes01
    I used Renner NB M600 high gloss nitro. Not much info about it on the net but I used it on three other guitars without any issues. Only difference in previous finishing was that after sending with 400 grit I didn't do another light clear coat but I continued with higher grits until 2500.
     
  8. jkes01

    jkes01 Senior Member

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  9. Freddy G

    Freddy G V.I.P. Member

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    this^^^
     
  10. Jure

    Jure Member

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    Thank you guys.
    Whatever they answer I will have to do something. First I will try to send to this »problematic« part. If this layer melting problem occurred after 400 grit sending (before last coat) there should be no problems. If this is deeper than I don’t know.
     
  11. Open_Book

    Open_Book Senior Member

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    Curious as to what it looks like on the Headstock.
     
  12. Jure

    Jure Member

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  13. Jure

    Jure Member

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    Here is the update.
    I sanded the entire top, removed the last coat and now everything is fine.
    It really looks like the layers didn’t melt. To be exact the last layer didn’t melt. Any ideas what is the reason for this? The only difference compared to other coats was that it was two weeks between coats and I sanded with 400 grit before this last coat but this shouldn’t be a problem since it is nitro.:hmm::hmm:

    Here is the picture of the same part as in the first post. Looking good and I am soooooo happy.:)

     
    jkes01 likes this.
  14. WhiteEpiLP

    WhiteEpiLP Senior Member

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    What was your mix on the last coat 50/50, 75/25?(laquer/thinner)
    More thinner equals faster dry time but maybe too fast of a flash that it didnt melt in.
     
  15. Jure

    Jure Member

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    Thank you WhiteEpiLP. Mix was around 30/70 (lacquer/thinner) but I am not sure this is the reason. As I understand the lacquer chemistry, drying is evaporation of thinner and other volatile compounds of lacquer. Evaporation time is a constant. More thinner would mean longer drying time. Of course I may be totally wrong here.
     

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