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Zpoxy for pore fill and grain enhancement

Discussion in 'Finely Finished' started by Freeman Keller, Mar 31, 2019.

  1. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    There seems to be several concurrent threads right now about pore filling and I seem to be the spokesman for a finishing resin called Zpoxy. I find myself repeating the same thing over and over, posting the same pictures and links. I thought it would be more efficient to just post one thread about this product and then I can point to it whenever the subject comes up.

    Disclaimer: I am not a finishing expert or "professional" or anything like that. In fact I am about as amateur as you can get. That might have some advantage for you folks who are finishing your first or second guitar and considering which products and methods you might want to use. I will certainly say that a professional who makes her living finishing lots and lots of guitars probably won't use this method.

    Second, there are lots and lots and lots of pore filling products on the market, and even more home brew methods. I've only tried a couple of them (which I'll talk about) but I'm not prepared to argue the merits of one over another. I'll try to show some photos of what works for me - if you have something your really like how about doing your own thread and showing your pictures.

    Third, of course, your milage and results may vary. In fact, they will probably vary a lot. Practice on scrap.

    Forth, always practice any finishing technique or product on scrap of the same wood that you will be finishing. Keep all the cutoffs from building your guitar for this purpose. Don't have any scrap? Get some.

    Fifth, I have only worked with lacquer on top of the finishing resin. I've tried both solvent based (nitrocellulose) lacquer and so called water born lacquer. Both work fine - I have had no problems with adhering, witness lines, blushing, or anything else. I can't comment on any other finish - practice on scrap.

    The product I use is a finishing resin called Zpoxy. I buy it from LMII but I think it is available elsewhere on the internet. It is a slow curing material, takes about 24 hours to completely cure. It has a slight amber tint to it that may or may not be desirable (practice on scrap). It is forgiving about mixing ratio - I don't weigh it but rather just squeeze about the same amount into a cup. A little seems to go a long ways - I have finished a dozen guitars with my first 12 oz bottles

    https://www.lmii.com/glue/3050-z-poxy-finishing-resin-12-oz.html

    Most epoxies are soluble in denatured alcohol (DA) - you can use that for clean up and to dilute the resin. When you first mix some DA in it it turns cloudy, but with some stirring it will clear. We'll talk about dilution later.

    OK, lets get on with it. Why "pore fill"? Some woods used in lutherie have small surface pores - they show up as fine little lines in the surface of the wood. Rosewood, mahogany, koa, some other hardwoods are porous. If you put many of the popular finishes over these woods the pores are not filled and they leave little lines in the finish. Here is a piece of EIR with nitrocellulose lacquer. It had one application of a commercial paste pore filler which either was not enough or shrunk back. The white lines is polishing compound in the pores

    DSCN1432.JPG

    Whatever product you are using for pore filling, the basic method is to apply it across the grain forcing it into the little pores. I do the same with Zpoxy.

    This particular guitar is a basic mahogany back and sides, spruce top and rosewood trim. Soft woods like spruce and cedar, as well as maple are not porous and do not need to be filled. We'll talk more about maple in a minute. Sand the entire guitar to 320, scrape the binding and purfling to get every bit of dust out of it and tape off wood that you don't want to get the resin on. Remember that this is your last chance to get the little scratches out - make it perfect.

    IMG_5138.JPG

    IMG_5139.JPG

    If you are going to do any staining, I think this is the best time. The wood is at its most absorbent and the resin will seal in the stain. Obviously this is very critical and definitely should be practices on scrap. This is a mahogany neck that I wanted to stain to match the cocobolo on the back. This isn't a good picture, sorry, but I've got a scrap of mahogany that I'm trying to color match to the scrap of coco, then I'll stain the neck in the background

    IMG_4022.JPG

    Here is the stained neck with the coco, its ready for pore filling
    IMG_4023.JPG

    For the pore filling itself I mix the resin 1:1 by approximate volume and simply work it onto the wood with some sort of squeegie - a plastic card works very nicely

    IMG_5140.JPG

    Get it as smooth as possible but don't worry - let it cure over night. Curved surfaces like a neck are a bit harder, just keep working it across the surface of the wood

    IMG_5141.JPG

    Sand it back level with the wood, you can start with 220 and go to 320

    IMG_5142.JPG

    Now apply a second coat. This time I mix the resin, then dilute it maybe 5 or 10 to one with DA. I just put a good splash in and mix it in thoroughly. The diluted resin can be applied with a little foam brush.

    IMG_5143.JPG

    Let that cure overnight

    IMG_5144.JPG

    and sand this back again level with the wood.

    (the forum software has told me I can't upload any more pictures so I'll post this and go on.
     
    Last edited: Mar 31, 2019
  2. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    I usually apply one more very thin coat of resin. I want this to soak into the wood and really bring out the grain. Again, its just a splash of DA but its probably about 10 to one.

    IMG_5147.JPG

    IMG_5148.JPG IMG_5149.JPG IMG_5150.JPG

    You can still see the pores, they will never go away, but they are completely filled and the surface is smooth. Here is a coat of vinyl sealer to start the transition to lacquer

    IMG_5158.JPG

    Here is another mahogany guitar with the resin on but no lacquer

    IMG_4727.JPG

    These guitars are pore filled and ready for lacquer
     
  3. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    However Zpoxy has another function which is why I really like it. You know how you wipe a piece of wood with DA or naphtha to see what the color and grain is going to look like under finish? Here is a piece of flamed maple with kind of an interesting browning tint. I wiped it with DA and took a picture while still damp

    IMG_4616.JPG

    All the time I was building that guitar I had the image of the color and flame of that wood in mind - it helped me decide what kind of binding and other details I wanted to use. When it got time to finish I knew I wanted that figure to be as dramatic as possible and I knew Zpoxy could help me.

    I took scraps of the top wood as well as the head veneer (also maple but a much lighter color) and I applied several different stains as well as both Zpoxy and thin CA, then shot some rattle can lacquer of the scraps

    IMG_4705.JPG

    From this I had a pretty good idea of which stains would work and that I wanted to put Zpoxy on to really highlight the figure

    IMG_4725.JPG

    The mahogany back and neck got the Zpoxy as before for just pore filling

    IMG_4724.JPG

    Here is that guitar with lacquer over the Zpoxy over the stain

    IMG_4809.JPG

    IMG_4810.JPG
     
  4. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    Lastly, how about a little gallery of guitars that were pore filled and grain enhanced with Zpoxy. This might give you some inspiration to try the products, obviously I'm hooked.

    Here is that cocobolo gutiar with the stained neck. Finish is nitro

    IMG_4381.JPG


    This is flamed Spanish cedar (which is neither from Spain or a cedar). The finish on this is a water born lacquer called KTM-9

    IMG_2128.JPG

    Brazilian and Madagascar rosewoods. Mahoghany necks lightly stained to match. Nitro

    IMG_2974.JPG

    Flamed koa with flamed maple binding. KTM-9

    Tricone 3.JPG

    Tricone 2.JPG
     
    Last edited: Mar 31, 2019
  5. tone57

    tone57 Tele-Meister

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    MMMM Mahogany

    Thanks for the beautiful explanation.
     
    Last edited: Mar 31, 2019
  6. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    Just a couple of comments/cautions:

    1. I strongly suggest applying sanding sealer (and sanding it back to what appears to be just about bare wood) prior to any staining or dye application. It's the only way you can get any control over color depth - if an area starts to go too dark you can use a solvent-dampened cloth to "pull" the color out and blend it evenly. Without sanding sealer - which contains specific fillers (that allow it to function this way) that shellac and standard clear lacquers do not - any more porous or softer areas of the grain can suck up the stain or dye, go "dark", and you end up with a blotchy stain/dye job.

    2. Thinning 100% solids epoxy or polyurethane resins is an "iffy" proposition because of the danger of solvent entrapment. Using them as fillers can work fine - but thinning can cause permanent, non-recoverable problems, which I have seen happen on dozens of projects. If the solvent soaks into the wood in a small, invisible "pocket" the resin can begin to harden above it, trapping the solvent. The solvent needs to evaporate - it cannot be part of the resin film or one or more bubbles will be created within the film; if it is able to partially evaporate pinholes develop.

    And if it is fully trapped inside both the resin AND the grain there can be eventual delamination - a separation in the film that causes a chip, sometimes pulling wood grain along with it. the solvents will never evaporate through the back of the wood if they are blended fully into the resin. It's always outwards.

    This is another good reason for using sanding sealer, as the sealing function makes it easier to work the unthinned resin film into the grain/pores.

    3. ALWAYS check the moisture content of the wood with an electronic moisture meter (about $25-30). For most coatings 11% is the maximum acceptable moisture content for coating; for resins IMO (and in the opinion of many manufacturers) 8% is FAR safer.

    Some get lucky using minimal thinning (10% would be the absolute maximum I'd even suggest attempting if you are dead-set on thinning - 5% or even less would be safer.) but these resins are not intended as grain fillers - and definitely not intended to be used as fillers if thinned! They are surface coatings meant to be used as packaged (after blending the components) that have been adapted as a grain filler.

    But it's definitely an "off label" method of application. I spent 35+ years in tech support and project management, much involving these coatings - and I do NOT recommend thinning. IMO you should only use them at full strength after the surface has been sealed.

    NO MATTER HOW YOU DECIDE TO USE IT, PRACTICE THE APPLICATION ON SIMILAR SCRAP WOOD FIRST. This is absolutely critical with 100% solids resins, which are NOT forgiving!

    I hope that helps - and I really hope you'll give these suggestions serious consideration. I've seen dozens of guitar bodies and other wood products permanently ruined through mis-application of resins.
     
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  7. jms2009

    jms2009 Tele-Meister

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    Freeman, thanks! Simply beautiful guitars. Your info in your write-ups is all very useful. You're a big help for all of us.
     
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  8. TwangToInfinity

    TwangToInfinity Tele-Afflicted

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    Thank you Freeman Keller !

    ive been reading about your zpoxy adventures for awhile and i am very interested so i am appreciative that you have gone thru the effort of this post for us!

    now i have tele decisions to make regarding zpoxy type finishing!
     
  9. eallen

    eallen Friend of Leo's

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    Thanks for sharing what has worked for you Freeman.

    Eric
     
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  10. djh22

    djh22 Tele-Afflicted Silver Supporter

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    Thank you Freeman! Your postings and advice have been a help to many of us.
     
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  11. Macrogats

    Macrogats Friend of Leo's

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    Great stuff Freeman. I know you’ve been through this process in your build threads, so thanks for posting the info into a separate thread I can keep and refer to for later use.
     
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  12. jms2009

    jms2009 Tele-Meister

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    Will zpoxy dissolve into itself ? In other words, after a 1st coat of it cures, can the 2nd coat be applied & melt into any zpoxy powder left on surface after sanding/vacuuming the 1st coat? I'm assuming it doesn't, & that my vacuuming of the 1st coat will need to be NASA/laser/extremely perfect, or else the pores will be cloudy from the powder I missed, right? I'm gonna use clear zpoxy on my Les Paul build & red/brown transtinted zpoxy on my LP Junior TV build.
     
  13. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    I don't think so, I think that once it has cured its pretty hard. However when I sand it back, if I wipe with DA the surface is slightly tacky so it may be softening somewhat. I also don't seem to get any witness lines so that tells me that there might be some bonding. I blow mine off with compressed air (probably a bad thing to do right before applying finish LOL) and sometimes wipe with a damp rag with DA.

    I have to be really careful with all of this. You have been told that this is not the right product or the correct way to use it. I'm quite sure that is true, so please use it at your own risk. All I know is that several people who I respect use and recommend it, and that I have had no issues with the Zpoxy itself (bonding, color, blushing, witness lines, compatibility with lacquer........). Your milage, results and all those other things may and will probably vary. You've been warned.

    However I like it and I'm looking forward to seeing your guitars.
     
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  14. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    No.

    With lacquer it's the solvents that melt each coat - regardless of resin type, nitrocellulose, acrylic or a blend - into previous coats.

    ZPoxy is 100% solids epoxy. Scuff sanding would be advisable before coating it with anything, as there's no chemical adhesion to a coat of cured (or partially cured) epoxy resin. It's hard and glassy-smooth. You have to rely on mechanical adhesion, and without some kind of abrasion of the epoxy there's nothing for an additional coat of anything to grab onto.

    Scuff sanding creates what's known as "tooth" - small, jagged irregularities in the surface that provide both variations in texture (which break surface tension) and increase the surface area that's to be coated.
     
  15. jms2009

    jms2009 Tele-Meister

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    Silverface, thank you too! I'll scuff with 220/320. I was originally considering sanding the zpoxy with 220/320/400, but I'll skip the 400 so the surface has teeth. Would I be even better off if I skipped the 320 too?
     
  16. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    This is a follow up. Its been a bit over a week. The guitar in post #2 (the mahogany OM) has received the three pore filling coats, two coats of vinyl sealer and a dozen of lacquer. It has NOT been wet sanded or polished in any fashion - the last coat of lacquer was reduced 1:1. I'm posting this to show that there are no pores, the lacquer has adhered to the finishing resin and, in my opinion, the whole process has been a success. Here is a close up of the guitar and neck

    IMG_5194.JPG

    I'll let this "cure" for a couple of weeks, then do the wet sanding and buff. Not bad for an amateur, eh?
     
  17. RiversQC

    RiversQC Tele-Meister

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    20190412_214615.jpg

    ;)

    Thanks for the thread! I'll bookmark it for whenever I get the chance to try this out.
     
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  18. Vizcaster

    Vizcaster Poster Extraordinaire

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    Freeman thanks for the enouragement - I tried z-poxy on a test piece of walnut over tung oil and got great results so this will definitely be in my arsenal from now on. Topcoated with Target WVX (waterborne hybrid alkyd varnish) without any adhesion problems oil-Zpoxy-WVX.

    In my case the tung oil on the test piece was cured for at least four or five months, but obviously for a finishing schedule I'd probably give it no more than a few days before sealing the grain. Have you had any adhesion problems with z-poxy over linseed or tung oil?
     
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