Sand paper

Discussion in 'Finely Finished' started by LunarSlingShot, Jun 19, 2019.

  1. LunarSlingShot

    LunarSlingShot Tele-Meister

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    Painting over a poly finish. What grit sand paper do you recommend using to scuff the finish?

    Will a scotch brite pad suffice? Steel wool?
     
  2. Blue Bill

    Blue Bill Poster Extraordinaire Ad Free Member

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    I would start with 400. If it seems too rough, go higher. 600 or 800 should be fine. (no pun intended.)

    I would guess steel wool would have a tough time cutting. Scotchbrite would probably work, but would take a lot more effort. Experimenting will answer your question.
     
  3. LunarSlingShot

    LunarSlingShot Tele-Meister

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    thanks, I just didn't want to use something way to rough to start with.
     
  4. jvin248

    jvin248 Poster Extraordinaire

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    320 is quite popular for this task, close to the 400 previously recommended.
    I have also heard that going much higher can be counter-productive as you are starting to polish rather than prep the surface for paint to stick to, think gear teeth and grip for that top coat.


    Steel wool should have 100 foot restraining orders on the box regarding guitars -- the broken bits find their way to the pickups, eventually abrading the magnet wire coating and shorting out your pickup in the worst case.

    .
     
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  5. Informal

    Informal Tele-Holic

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    If you're refinishing your guitar with the pickups still in place, you deserve all the bad things that follow. :p
     
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  6. LunarSlingShot

    LunarSlingShot Tele-Meister

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    exactly what I was thinking.....I've already completely disassembled it.
     
  7. eallen

    eallen Tele-Afflicted

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    To get new finish to adhere well to a current one, except laquer on lacquer, use 320 and no higher than 400 grit. The surface needs some texture for the new to grab ahold of.

    Eric
     
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  8. LunarSlingShot

    LunarSlingShot Tele-Meister

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    Do you think 220 is too coarse?
     
  9. telepraise

    telepraise Tele-Meister

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    220 should be OK if you're putting a thick, opaque color coat down. Wet/dry auto paper with a lubricant is the most pleasant way to do this task.
     
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  10. Finck

    Finck Tele-Afflicted

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    In my opinion, use a paper that's is just sufficient to let the surface dull. Too coarse grit and you'll end with unnecessary scratches, too fine grit and you'll get no results. Personally, I'd choose 400 or even 600 wet grit (last one using more pressure than usual on a polish job). But it's just me...
     
  11. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    I don't understand how anyone can answer the question. There is absolutely not enough information.

    "Painting" with what? Over what "Poly" finish?

    "Poly" has become a generic term for just about any glossy, non-lacquer guitar finish, most of which, on newer guitars, are not conventional polyurethanes or polyesters.

    "Painting", on the other hand, is not generally a term used for guitar finishing, which does not involve conventional "paints". "Paint" generally refers to oil based and water based enamels and water based wall paints.

    For some finishes suitable for application over polyurethanes and polyesters sanding alone would not be recommended. A coat of adhesion promoting primer may be necessary in addition to sanding. The same may be needed over a finish you *think* is a "poly".

    So it's critical to know what you plan to apply and what guitar you are finishing (specific brand/model/year could be very helpful).
     
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  12. LunarSlingShot

    LunarSlingShot Tele-Meister

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    I am refinishing a classic vibe custom telecaster (2015-17 I think?). The bridge has been cut in half and it had been routed for a humbucker in the bridge (poorly in my opinion). So it will never be a true telecaster anymore. decided I would just take it a step further and (to cover the poor routing) I would turn it into a tele deluxe with the big pickguard.

    I plan on shooting over it with rattle cans.
     
  13. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    Which is coated with a thin-film, catalyzed, hard polyester finish.

    Sorry, that's not enough info yet. "Rattle cans" contain anything from oil-based enamel to shellac to lacquer to urethanes to water based finishes, heat-resistant coatings, epoxy-fortified coatings, textured paints and compressed nitrogen.

    The question was "what *coating* are you thinking of applying?". Some require sanding; some require sanding and primer; some can't be used at all if you want even minimal durability.

    Also - what color(s) is it now and what color do you want to use? That also may affect the issue of priming or not priming.

    Have you done any research into wood refinishing and/or guitar refinishing? Read info on finishing or manufacturer's websites, or any books on the subject? Do you have any previous experience?

    I'm asking because you supplied minimal information in your original post that wasn't sufficient to answer any question at all, and your followup seems to imply you don't know much about coatings (i.e. the use of the term "rattle cans" alone). There's no insult and I'm not beating on you - but if you want help you need to supply a LOT more information, which probably means you need to educate yourself a bit more in the basics. the forum can be used to get advice, but we can't teach you the entire process - that would take pages of information.

    Make sense? If you have the additional info great - please post it. If you're unsure, do research *first*.

    I'm honestly more disappointed in those who provided answers to your question. Unless they are mind readers they couldn't possibly know what you were going to "paint" with, making every single response invalid.

    Guesses of that type are equivalent to throwing darts in the dark, and do a disservice to the OP
     
  14. Blue Bill

    Blue Bill Poster Extraordinaire Ad Free Member

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    Sorry to disappoint you, dude. :oops:
     
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  15. LunarSlingShot

    LunarSlingShot Tele-Meister

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    I am planning on using Krylon colormaster spray paint plus primer (all in one can) I am going with a sort of turquoise blue. The original finish was Sunburst

    I have very little refinishing experience
     
  16. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    Ok, that information really helps me help you!

    First - that is an enamel spray paint. OK for old bikes, metal shelves, railings etc - but a poor guitar finish. First, to apply it over a catalyzed polyester sanding alone will not be enough to get decent adhesion. The "primer" in it also makes it a sort of compromise - not the best primer (but some anti-staining qualities) and that gives up some of the quality of the finish, l which is already low for guitar use.

    You will still need a properly-fitted cartridge-type respirator and full (goggle type) eye protection and a well - ventilated area for safe spraying, with no flames (including pilot lights) in the area. Also pay attention to the temperature and humidity and make sure it's within the requirements spelled out on the product data sheet.

    I suggest thorough sanding with 180 grit Fre-Cut using a rubber sanding block. You can but kits of small ones for inside curves of cutaways on Amazon or at Rockler stores.

    Then apply a very thin coat of an adhesion-promoting primer - XIM, BIN or KILZ (check and get a solvent based version used both as a primer/sealer and adhesion promotor, as they all make several products.

    Then apply the finish in very thin coats using multiple "passes" per coat. Let each coat dry thoroughly per the manufacturer's product data before recoating.

    Try ALL of this on some scrap wood before working on the guitar. You'll probably need several coats of primer to simulate the smooth surface, but the purpose is to learn how to spray the finish smoothly and consistently, and how to fix problems BEFORE they happen on the guitar. When you have it reasonably smooth you can try finish wet sanding with 1000 wetordry and see if the stuff will wet sand at all, or whether it gumballs when you try to sand. Many enamels do, and when you're done spraying what you see is what you get.

    Whether you can sand and buff or just leave it alone, it is what it is - a "paint" finish. It may look great short term, but don't expect it to last as long as lacquer or polyurethane (or polyester, normally factory applied) finish. It's simply not very durable - poor solvent resistance, abrasion resistance and impact resistance; colorfastness varies depending on light exposure; they tend to stick to rubber and plastic on guitar stands; they discolor easily if exposed to certain cleaners, fingerboard oils, electronic cleaner/lubricants and polishes.

    Those are the good and the bad points. FWIW I never recommend enamel finishes on guitars. If you're not able to do lacquer or polyurethane work for some reason I suggest paying someone to refinish the guitar. Because in anywhere from a few months to a few years you're going to need it redone anyway.
     
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  17. LunarSlingShot

    LunarSlingShot Tele-Meister

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    I would definitely be willing to take a suggestion at a different type of spray paint to use as I haven’t bought the paint yet. Any brands or types you would recommend?
     
  18. SacDAve

    SacDAve Poster Extraordinaire

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    Mowhawk products are really good, Also some paint stores will put paint in aerosol cans for you, your best bet is to find a paint store that sells auto motive paints. Some places don't offer that up you have to ask.
     
  19. SacDAve

    SacDAve Poster Extraordinaire

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  20. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    as @SacDAve mentions, start with the Reranch site. Mohawk products are excellent, but if you have essentially NO experience spraying lacquer there's a LOT to learn.

    It's not just a type of "paint" - in fact you should just drop the word "paint" completely, as the products generally discussed/recommended are "wood finishing systems" - even is applied over a previous finish.

    Even though you are not starting from raw wood, reading the info on the ReRanch site - especially finishing 101 - will teach you some basics. But because of your "recoating" situation you don't need ALL the products - and you're going to have a limited color selection. Be cautious of YouTube videos - any amateur who thinks he's smart can play "expert, and there are some terrible and downright dangerous ones out there!

    Same with advice on forums - you need to qualify the sources. Find out who is giving you advice and if they have a solid background, as you could be getting advice from an industry professional, experienced amateur, somebody who's finished one guitar (badly) or a 14 year old kid who has only painted plastic models, doesn't play guitar - but likes to type! o_O

    Now some basic tips (based on decades of experience and tech support):

    First - you need to hang of somehow suspend the body vertically. If you spray "flat" it will be uneven - thicker close to you and thinner further away, with tons of overspray. You want an even, consisten distance between tip and the work, and always works from top to bottom to avoid overspray landing on just-coated areas (causing "dry spray - a sandpaper like texture)

    The primer has already been mentioned - after thorough sanding, an adhesion promoter that's compatible with lacquer (BIN, XIM or KILZ makes them); then very light coats of a colored lacquer, applied in 3 VERY light passes for each coat. Unlike "paint", these coats should NOT fully cover! You need to work slow and build up the finish. Lacquer melts into previous coats, so as it builds it will fill in and start to flow after 5-6 coats if applied properly.

    I suggest avoiding Colortone and Deft lacquers, BTW. They are good products, but they dry VERY slowly. Lacquer dries ONLY by evaporation of the solvents - there is no "curing" - and conventional lacquer coats should dry in 30-60 minutes; those take hours!

    DO NOT sand between coats of lacquer, ever. Let the material level itself out. Only spot-sand small runs, if any. Remember - be patient, go slow, spray thin coats.

    After the color, apply several coats of clear gloss lacquer the same way. I you do it properly, when you finish you should be able to buff it the next day - surface sanding should not be needed and is a repair procedure to fix uneven application.

    And as mentioned before, do ALL of this on scrap wood first, and practice until you can do it right. The most common cause of finish problems is impatience /lack of practice. It's not difficult to do, but is VERY different from any spray painting you have done in the past.

    Last (really FRST) - you MUST have a clean, well-ventilated work area; a cartridge respirator that fits properly and has the right cartridge and prefilters for lacquer - otherwise you end up breathing dangerous - even deadly -fumes, Dust masks are useless! Also wear full-coverage goggles for eye protection - overspray can drift around the edges of glasses (even safety glasses).

    Try to buy the respirator at a professional paint store - not online or at a hardware store. They only work if they fit, and should be fit-tested by the seller; most contractor-oriented paint stores have people with respirator fit training.

    This is all VERY basic information - you should do a lot of reading. you'll read different opinions about how to apply lacquers, but for beginners the "3 ultra-thin pass per very thin coat" method is the best way to get to a smooth end result. It also avoids problems caused by trying to apply "full" coats, which inevitably end up too thick and trap solvents underneath. This results in wrinkling, blisters, peeling, soft coatings, and systems that never fully dry.

    Get the safety gear, make sure the space is clean, ventilated, free of all sparks, flames and pilot lights, (and fumes won't bother anyone else) - then read hours worth of material and practice spraying the ENTIRE system on primed (or previously coated) scrap wood, and don't start on your guitar until you understand how the products work, interact, and can get a decent finish!

    Good luck!
     
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