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Thread: Water???

  1. #1
    Join Date
    Jun 2007
    Location
    Wichita, Kansas
    Posts
    1,795

    Water???

    Trying to teach myself a new skill and so far, as you can see from the attached photos, it's been an unmitigated disaster.

    The pictures show an attempt to spray zinnser amber shellac, diluted 1:2 with alcohol, and tinted with transtint dark walnut. The substrate is Baltic Birch. Equipment is just a regular old siphon fed spray gun off a regular old compressor - no HVLP setup. Pressure was 40psi at the regulator about 25 feet of 3/8 hose away from the gun. No dryers or filters installed.

    The defects are not bubbles. Rather they are holes in the finish coat. Is this the result of water in the lines? I don't believe there's any contamination on the surface but I won't bet the rent money on it. The surface had just been wiped clean (using denatured alcohol) of a previous brushed coat of the same tinted shellac which didn't display the effect shown.

    All comments welcome as long as you recognize this is my first attempt at spraying shellac and is a learning exercise for me.
    Attached Images Attached Images
    Tom Veatch
    Wichita, KS
    USA

  2. #2
    Join Date
    Jul 2008
    Location
    Tomball, TX (30 miles NNW Houston)
    Posts
    2,747
    I just finished a job with about 30 gallons of shellac. Yes we sprayed it. If I had to guess I would say oil in your lines. OR Water in your DNA...or your wood.

    Does the pattern follow the grain is is that just an illusion? If it does, did you let the DNA completely dry before you sprayed it? You may have left water from the DNA in the wood.

    You should be able to sand it away or wipe it away with DNA.

    Check you DNA make sure it's fresh. Kansas doesn't have as much humidity as HOuston but DNA will absorb moisture from the air.
    Scott

    Finishing is an 'Art & a Science'. Actually, it is a process. You must understand the properties and tendencies of the finish you are using. You must know the proper steps and techniques, then you must execute them properly.

  3. #3
    Join Date
    Jun 2007
    Location
    Wichita, Kansas
    Posts
    1,795
    Quote Originally Posted by J. Scott Holmes View Post
    Does the pattern follow the grain is is that just an illusion? If it does, did you let the DNA completely dry before you sprayed it? You may have left water from the DNA in the wood.
    That's a coincidence, I think. My guess is that it's following the track of the gun/spray pattern which just happened to be in the grain direction. The previous cleaning was done about an hour before spraying this mess. So the DNA should have dried completely. The DNA was from an almost empty can, so an appreciable moisture content is a distinct possibility. Oil in the lines is also a possibility. The compressor is an oiled type and I could be getting oil mist in the line. But, I've sprayed quite a bit of oil-based paint using this rig and haven't noticed any problems like this.

    You should be able to sand it away or wipe it away with DNA.
    It's a bit of a hassle, but, yeah, it shouldn't be that much of a problem stripping it back to (relatively) bare wood.

    Check you DNA make sure it's fresh. Kansas doesn't have as much humidity as HOuston but DNA will absorb moisture from the air.
    Bought a brand new gallon can this afternoon. Should be fresh and dry. Real tempted to spend some of my kids' inheritance on a point-of-use dessicant air dryer/filter. Can't hurt, might help.

    I agree with the comment on Wichita vs Houston humidity. Born and raised in the piney woods of Louisiana and that's about like Houston. Folks around here don't believe me when I tell them, in that part of the country, the summer temperature numbers and humidity numbers are about the same. Temperatures don't get much above 95 all that often and the humidity don't get much below 90 all that often.

    If summer here is like being in a oven, summer there is like being in a pressure cooker.
    Tom Veatch
    Wichita, KS
    USA

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