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Epoxy wood filler
Does anyone out there have any advice for me on using two-part epoxy as a filler on open pore woods such as East Indian Rosewood?
I've made a several guitars now and have up to now used water-based paste wood fillers such as Timber Mate or nothing at all under a Tru-Oil finish when working with open grain woods. On my next project though, I'm thinking of using a clear epoxy filler but have zero experience with it. I did a quick search, but the only products made specifically as wood fillers seem to be pastes, which doesn't seem like is what I want. There are liquid epoxies, but some reviews say they never dry hard and remain tacky. Does anyone have any guidance for me on what product I should use? I would also appreciate any advice I can get on application. |
#2
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I don't build guitars, I pound on 2x4s with rusty crow bars...
but you might want to look into Abatron's WoodEpox... There's a paste and a liquid. 50/50 mix. Don't use it in the cold to avoid permanent-tacky. I used some liquid recently and notice how clear it is set up. I mixed up enough during the hot summer to paint something outside with, it started generating its own heat while mixed up in the can after a few minutes. -Mike |
#3
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I've used epoxy as a pore filler on a number of guitars. I use West System myself simply because I have it on hand but I've read of others, including a well-known luthier, even using the 5 minute hardware store type. Don't let the 5 minute type fool you into thinking that it's faster. It sets up quicker but really isn't ready to sand until it fully hardens which is about the same length of time as a slow set epoxy like West System.
I've used small squeegees and credit card sized applicators and prefer using an old credit card. Some wipe it on and off with paper towels. The principle of application is exactly the same as using paste fillers: try to leave on as much as possible in the grain while removing the rest. 2- applications are usually needed, sanding between coats. After the grain is filled the ideal is to remove everything from the surface by sanding while not sanding so much that you reach the bottom of the grain that's been filled, causing you to apply another coat. |
#4
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5-minute epoxy is faster. Not because you don't need to let it harden overnight; you do, but you can handle the guitar and do the parts you didn't start on much sooner.
Some things that work for me: First, spray a thin coat of shellac before filling. Mix a small amount--no more than you can get on before it sets up. This also makes it easier to get an even 50-50 mix, because you can judge how much you have squeezed out of the tube more easily. The right amount is about the size of a large chocolate chip each of resin and hardener. Mix thoroughly, using a craft stick. It's well worth having less working time and putting on a smaller amount at a time in order to get a thorough mix. Wrong proportions and insufficient mixing are the reasons epoxy stays sticky, 99% of the time. My rule of thumb is to mix until you think it is well mixed, and then keep mixing for as long as that took. Use a dulled edge (400 grit is good), corners rounded single edge razor blade for a squeegee. Squeegee in the direction of the grain, with enough pressure to force the epoxy into the pores. Angle the squeegee a little so excess will get pushed into the next unfilled area. When you feel it starting to set up, STOP, wipe your razor blade clean with a small scrap of cloth that is wet with denatured alcohol, and quickly use the blade to clean off any epoxy not yet squeegeed down. But it's better to run out of epoxy before it sets than to clean off excess that is setting up. Try to leave as few ridges as possible, because they will be a hassle to sand out. Wipe the blade clean again, and go on to the next section. If you want a good fill, after it has hardened overnight, sand back to bare wood and do it all again. Then sand back to bare wood before finishing. I've never found a product made for pore filling that I liked. The worst have been the clear water-based ones; they tend to bridge the pores so they look filled, and then they sink way down under finish. But there is no great pore filler that works they way you would hope them too; there are only bad and less bad ones. If I want a colored fill, the best thing I've found is drywall joint compound mixed with powdered artist's pigments.
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"Still a man hears what he wants to hear, and disregards the rest." --Paul Simon Last edited by Howard Klepper; 11-12-2023 at 02:14 PM. |
#5
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You have a couple of options. You can use Zpoxy, System 3, or West Systems.
There may be other offerings out there BUT you must ensure that they don't amine blush. That's the waxy coating that can form on top of the epoxy. Amine blush can absolutely cause huge finish issues ... so stick with the Epoxy formulations that are designed specifically for base coatings beneath a Top Coat. I use West Systems 105 Resin with the 207 Clear Hardener. You add silica thickener to about the consistency of Mayonnaise. You can seal the guitar beforehand or use the Epoxy as your sealer. If you sand back to wood, just mix some non-thickened Epoxy and wipe the surface to ensure an even appearance. My advice is to seal the guitar with the wood sealer that goes with your finish system. Then scuff sand the guitar and then pore fill. It will probably take at least 2 applications for woods with deep pores. With epoxy, you can add a second coat while the 1st coat is still tacky. Once it dries to the touch, you have to wait 24 hours and scuff sand again to get the necessary mechanical adhesion. Hope that helps. Finish work is the one aspect of the majority (IMO) of luthier-built guitars that quite simply ... do not measure up to what is being done by manufacturers and small shops. For this reason, a lot of builders outsource their finish work to a few different Finish Guys that generally all do good to excellent work. |
#6
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I think there is two schools of thought here. I've only used epoxy once so I am admitted not an expert. I used 5-minute as per the French Polish instructions I was following. With 5-minute you sand back to wood. IMHO that is how pore fillers are supposed to work however I believe the other school of thought is to finish on top of a coating of epoxy and I've seen Z-poxy used for that to pop the figure and to give an amber color.
So some sand back to wood while others use the epoxy as a sort of sealer or foundational coat. |
#7
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Whatever system is employed, they all have a learning curve, and ain't none of them fast or easy. Patience counts. With epoxy, neatness is a paramount need. That, and a heap of cut-up paper towels and always use disposable gloves when there's epoxy in process.
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#8
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Whilst not everybody has access to it, uv pore filler, is the bees knees IMO, the surface comes up like glass after two rounds of filling / curing / sanding
Have used shellac, epoxy (5 minute and z poxy), egg whites, acrylic fillers, tried most pore fillers etc, hands down uv filler is the best for me Steve
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Cole Clark Fat Lady Gretsch Electromatic Martin CEO7 Maton Messiah Taylor 814CE |
#9
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Check out Driftwood Guitars on YouTube. I believe Chris uses epoxy as a pore filler.
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#10
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#11
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It's not epoxy, but I have recently used GluBoost Fill and Finish (CA) on an open pored mahogany neck. I also used it on the top over the rosette and purfling gaps.
I found it very easy to use and scrape down - it is a flexible CA as opposed to the usual brittle CA. GluBoost also sells tints that are very powerful. They included a small packet as a sample with my order and I was amazed at how little was necessary.
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#12
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I have used epoxy mixed with wood dust to fill the open rims of abalone inserts in a striped ebony fingerboard.
The result was disappointing to me because the epoxy darkened the mixture and was obvious after curing. I dug it out again and used a liquid called "wood mass solution" to make ones own wood putty. This hardened very quickly and was almost invisible because the color of the wood dust hardly changed.
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#13
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I googled that and didn't see a product. You you provide a link?
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#14
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Tags |
filling, finishing, pore fill |
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