So this happened: Nitro Help Needed!

Discussion in 'Luthier's Corner' started by NathOBX, Mar 6, 2019.

  1. Keep spraying and sanding till it’s level

    0 vote(s)
  2. Sand it all off and start over

    3 vote(s)
  3. Carrots

    1 vote(s)
  4. Fire the drummer

    3 vote(s)
  1. 7E51EE4F-F2D4-4F9D-BAA0-709316AD5530.jpeg
    So this happened... I’ve been spraying stewmac sonic blue nitro in a can. I guess it gets colder in my basement than I thought:( Should I A. spray over it and keep sanding until it’s level. B. Sand it all off and start over. Also before this happened I was having trouble building finish around the truss rod hole, any tips?
  2. Manton Customs

    Manton Customs UK Luthier

    Jan 31, 2014
    Shropshire, UK
    Luthier, Manton Customs
    It looks like it might be lifting rather than just checking. So there could be an adhesion issue. Perhaps there was some grease round the truss rod rout as you mentioned it wouldn’t cover well there.

    So Acetone wouldn’t be a bad idea. It’ll completely strip it and should take care of any contaminants.

    Funny how Nitro is evil stuff on TB but the best thing ever on most other forums...
  3. Could it be from putting on too many coats without a proper cure time?
  4. This is my thoughts too: something contaminated the surface causing the wood to reject the lacquer in certain spots. Hopefully it's something relatively easy to remove like grease or wax and not something like silicone contamination that can plague finishes and manage to survive sanding and cleaning.

    Sand it off, clean the wood with acetone and try again. Maybe lay down a coat of shellac on the bare wood as a sealer coat. Shellac sticks to everything and everything sticks to shellac.

    I've sprayed Nitro down into the 40s and the only issue I've noticed is increased drying time. I don't think your problem is caused by cold.
    Dadagoboi likes this.
  5. I used dewaxed shellac as a sealer
    Last edited: Mar 7, 2019
  6. So I spot sanded the checked spot down to almost wood and resprayed, so far so good.
    SlingBlader likes this.
  7. Update, I have waited for warmer weather and better humidity and things seem to be going well. I have done the color coat on the body and the headstock. The body currently has six coats of clear over the sonic blue, neck currently has eight. Given my experience with wet sanding and buffing I’m going to try for 15 coats total before I start wet sanding to give myself a little space is this a bad idea?
  8. I don’t have experience with the StewMac spray cans but I know that spray cans typically go on pretty thin so it’s hard to lay down “too much.”
    NathOBX likes this.
  9. Manton Customs

    Manton Customs UK Luthier

    Jan 31, 2014
    Shropshire, UK
    Luthier, Manton Customs
    Depends on how heavy/light you’re spraying. If you’ve been misting it on and doing one pass each coat, you’ll need more. When people refer to a coat with Nitro it usually equals three passes, so a pass is made then left a minute or so for it to get nearly touch dry, then another pass and repeat once more. That’s a coat in Nitro terms. A good rule to stick to is the rule of three....This is -

    3 passes per coat
    3 coats per day
    3 days spraying

    So that’s 9 coats or 27 passes. You also have enough room to level sand at the beginning of each day with that.

    That’s a pretty fool proof way of knowing you’ve got enough lacquer down. Don’t worry too much about getting a thin finish, Nitro will outages and shrink, so eventually it’ll become thin by itself just like vintage instruments have done.
    Matt Liebenau likes this.