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Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

Cleaning between coats

Discussion in 'Finely Finished' started by AlterEgo, Aug 21, 2017.

  1. AlterEgo

    AlterEgo Tele-Meister

    249
    Apr 8, 2014
    Portland, ME
    Curious what folks generally use to wipe off residual dust from sanding between clear coats. After all these years I still occasionally have an issue in between leveling my clear where I get a few spots of clouding which I can only attribute to trapped residual contamination. I use water based clears and have always wiped down with a cloth lightly dampened with mineral spirits. I always let it dry out for about thirty minutes before proceeding with my next coat so I know it's not wet. It's rare that it happens and of course it's most visible over a black base coat which is what I'm doing now. It's not the end of the world, I'll just sand it back down but the couple times a year I run into this is irritating so I thought I'd see what everyone else does. Thanks
     

  2. Dacious

    Dacious Friend of Leo's

    Mar 16, 2003
    Godzone
    Tack rag. Any auto refinishing store. Sticky cheesecloth that leaves the surface perfect.
     

  3. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    65
    Mar 2, 2003
    Lawndale CA
    Between clear coats of polyurethane? A tack rag as previously mentioned.

    There is no sanding between clear coats of lacquer. It is a waste of time - each coat melts into the previous one eliminating all signs of individual "coats".

    Lacquer "clouding" is called "blush" and is moisture contamination. Don't spray if the humidity is above 50% and if you get clouding, mist "blush reducer" - don't sand. Sanding may still trap moisture that you can't see.
     

  4. Vizcaster

    Vizcaster Friend of Leo's

    Sep 15, 2007
    Glen Head, NY
    I use Target Coatings water borne finishes and they recommend against using mineral spirits until the finish is really fully cured, so that means not between coats and not for wet sanding. Mineral spirits is oily enough that it won't mix with water and any residue may cause adhesion problems or worse (cloudiness).

    Instead i use a 50/50 mix of denatured alcohol and water, liberally dampening a paper towel (or disposable paper "shop towel") folded into quarters. Works great for removing sanding dust and cleaning off any contamination that may have settled on the workpiece from one day to the next. The alcohol can temporarily soften some waterborne coatings, but it serves to help adhesion if you're using a coating that does not burn in to itself.

    Pre-packaged "tack rags" are nothing but thinned down varnish on a piece of cheesecloth. It's certainly not compatible with water based coatings and IMHO not worth the cost even if you're using regular oil based varnish.
     
    AlterEgo likes this.

  5. AlterEgo

    AlterEgo Tele-Meister

    249
    Apr 8, 2014
    Portland, ME
    That's exactly what I was looking for, thanks. WB coatings have their own quirks, most I have figured out since transitioning years ago but this one alluded me. I knew tack rags were a no no but I didn't realize mineral spirits were too. I've used DNA before with kind of an odd result. Have you ever experienced DNA completely dulling the gloss of a finish before? Maybe it was because I hadn't properly diluted it but it just about ruined a finish for me previously. That was with Varathane.
     

  6. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    65
    Mar 2, 2003
    Lawndale CA
    Oops - Somehow I missed the "waterborne" reference in the OP. What I posted is still good reference material to be aware of.

    FWIW most pro painters/fine-finishers I know use tac rags with waterborne finishes because of the superior dust pickup. They follow it with a light naphtha wipe (regular Ronson lighter fluid works fine for DIY jobs), which removes all oils and leaves no residue. May techs keep naphtha around at all times for oil, grease, sticker glue/related removal, fretboard cleaning etc. Safe around all plastics and all finishes (except enamels - which aren't very good finishes to start with).

    Denatured alcohol, water and (or a mix) don't have the same kind of dust adhesion tac rags have, which is the whole purpose of using them. Solvents of any type alone almost always leave microscopic and hard to see dust particles that can contaminate the finish.

    It's worth trying on test pieces to see how you like it. Hope it helps -
     

  7. Vizcaster

    Vizcaster Friend of Leo's

    Sep 15, 2007
    Glen Head, NY
    I seem to recall reading chemical-resistance tests where straight DNA would temporarily dull the water borne finish but the gloss returns when it has a chance to dry again. That's not my idea of chemical-resistant, but it's certainly a lot better than the white chalky mess you get if DNA gets onto nitrocellulose lacquer! I keep a jelly jar of 50/50 DNA/water, a couple of paper towels, and a toothbrush handy when spraying. Some spray guns build up a little bit of finish on the nozzle (especially bleeder-type HVLP guns where the air is always going through and the trigger only controls the fluid) and a toothbrush dipped in the 50/50 mix will clean up the spray gun tip.
     

  8. old wrench

    old wrench Tele-Meister

    In the past, I always used the regular old yellow cheesecloth type tack rags like ya'all are talking about, but a couple of months ago I saw that Harbor Fright was selling a different type so I figured I'd give one a try. I like them! They are are blue and treated with something much different than the yellow ones. They do an excellent job of picking up that pesky dust that likes to cling on. The price is pretty good too - 59 cents a piece.
     

  9. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    65
    Mar 2, 2003
    Lawndale CA
    A very light mist of blush eliminator (or reducer) takes care of this in seconds.
     

  10. AlterEgo

    AlterEgo Tele-Meister

    249
    Apr 8, 2014
    Portland, ME
    If only blush eliminator existed for water based!
     

  11. Vizcaster

    Vizcaster Friend of Leo's

    Sep 15, 2007
    Glen Head, NY
    No joke, the chemist at Target Coatings recommends using chicken warmer bulbs to cure the finish and help the moisture to off-gas and it might clear up blush (I used to moderate the luthiers' section of their forum).
     

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