Z-poxy Pore Fill - Luthier Tips du Jour Mailbag
In this episode, Robbie O’Brien shows how to apply Zpoxy brand epoxy as a pore fill.
Video Transcription
[on-screen text reads: Luthier Tips du Jour Mailbag]
Mailbag question: Do you use epoxy for pore filling? And if so, how do you apply it?
Robert O'Brien: Today's Tips du Jour Mailbag question comes to us from Alaska. "Robert, do you ever use epoxy for pore filling? And if so, how do you apply it?" Matt in Alaska.
Matt, thank you very much for this question. I actually get this question quite a bit. I've used just about every pore-filling method and product available to man, and all of them work. Epoxy is just one of the tricks that I have up my sleeve for pore filling. Now, not all epoxies are created equal. I like to use a brand called Z-poxy. I get it from LMI, and I use item PT-40. It's a finishing resin. It's not an actual glue like a normal epoxy. They do make other types of epoxy, but the finishing resin is the one I like. It's for leveling, and it levels and sands easily.
Day 1: How I apply Z-poxy as a pore filler
Let's go over to the bench, and I'll show you how I apply Z-poxy as a pore filler. Matt, here's the Z-poxy finishing resin that I mentioned. PT-40. It's actually a two-part product. It's got a hardener and a resin. And you have to mix them.
Now, one of the reasons why I like the Z-poxy brand, unlike other brands, is that the mix ratio is very forgiving. You don't have to weigh it out like a lot of other brands of epoxy. You can just eyeball it and mix it, and it works just fine. If you happen to get a little bit more hardener than resin or vice versa, it's still going to work for you.
Because it is an epoxy, you want to take precautions. I like to wear some gloves so that I don't get it on my skin. You also want to work in a well-ventilated area or perhaps even use a respirator.
Mixing the epoxy
To mix the epoxy, I just eyeball it. I'm going to start with the finishing resin here. And now the hardener or vice versa. Maybe I got that backwards.
[Robert poors some finishing resin, then some hardener in a small clear plastic container]
And one is a little heavier than the other. It's very easy to just look sideways at it, and you can see how much you've put in there. And, to me, it looks like I have a little bit too much of the clear. I want to put a little bit more of the amber color in there. And since they don't mix until you mix them, you can kind of see how much of each one you have there. And these little plastic mixing cups work really well. Now, I come in and just stir it.
Applying epoxy to the back
Now, there are several different ways to apply epoxy. The way that I like to do it is to put it on and then let it sit overnight. I'll scuff sand it the second day, and I'll apply a second coat. After the second coat, I sand it all the way back to bare wood. The reason for that is because you could have compatibility issues with the top coat, the other finishes that you put on. Another reason for that is that, when you're sanding the second day, these layers are so thin you're going to go through the wood, and you're going to have blotchy areas. Now, the remedy for that and what some people like to do is mix up a third batch and dilute it 50/50 with alcohol and then wipe it on with a paper towel like water. What that does is even out your color. And then you go over the top with your top coats.
I have heard of compatibility issues. However, there are things you can do, like add a layer or seal coat or shellac over the top of that, and you're usually okay. I've done it both ways. I just prefer these days to go ahead and sand it all the way back to bare wood.
The Z-poxy is now ready to go. I'm going to put a little bit on the surface. What I use is just a little squeegee.
[Robert starts working the epoxy into the back of the guitar body with the squeegee]
Notice that I'm working across the grain. I find that I get better results doing it that way than going with the grain. I'm also kind of working it down into the pores. Now, I failed to mention that, before I even got to the stage, I thoroughly sanded my guitar up to 220 grit, and then I vacuumed all of the dust off and blew the dust out of the pores because you want to make sure those pores are open so that you can get the Z-poxy or whatever pore filler you're using down into them. If not, you're just covering them. And then when you sand, you wind up exposing the pore again.
I am not worried about keeping it extremely clean at this point. In other words, with no marks from my squeegee. Because I'm going to hit it again tomorrow with a second coat. I also like to put newspaper on my bench so that I can keep my bench clean. It also serves the purpose of allowing you to keep current on the events around the world as well as the local sales going on in your neighborhood at the stores.
Now, you want to be careful not to get messy and get it all running down the sides and dripping. Try and avoid that.
When you get enough on the back, if you want to come in, and you have excess on your squeegee, just begin wiping it on the side because that's where we're going next.
By the way, Z-poxy works very well under waterborne finishes that don't have that nice amber color. You can use the epoxy to pop the grain.
All right. The first coat soaks it up quite a bit. And rosewood has craters for pores, so you'll wind up using it. Next thing we're going to do is start working on the side.
Applying epoxy to the sides
Now, for working on the side, I'm using my vacuum clamp that I got from LMI. It makes it very convenient to work on the side. You'll notice that the top of my guitar is not sealed. That's because I'm not done building this guitar yet. I'm on day three of a private guitar-building class with a student here, and we're getting a jump on our finishing by go ahead and starting our pore fill, since it's a two-day process. The neck is not completely carved. However, I have gone ahead and carved the heel so that I can get right up in there with my finishing resin or my pore fill.
It's not the end of the world if you get a little bit on the top. However, try and avoid that so you don't have a lot of cleanup work to do on that later.
Now, the nice thing about the LMI vacuum clamp is that you can spin it around and swivel it up and down, do all the kinds of things with it, to make it more convenient to work with.
[Robert pours some epoxy on the guitars side and works it into the grain by working the squeegee up and down the sides]
Now, I've swiveled over to the final side here.
Now, on day two, you're probably going to use about half as much epoxy as you're using on day one because, like I said, wood really soaks it up on day one.
Now, when you come in and work on this area here where the neck is, and I'm working on a classical guitar, and I've build my guitars with the neck on, you want to make sure you don't leave a lot of residue in there or you're not going to be able to get that blue tape off. Any residue now gets wiped on the paper on my bench. I'll also come in and run a finger right along there just to make sure they have no runs or drips in that area. Something else I like to do is run a finger around the edge like that. Sometimes right on the edge of the binding, there'd be a run or a drip. You go ahead and do that on both the front and the back side.
Applying epoxy to the peghead
If you decide to use a wood that's porous on your peghead, don't forget to fill that as well. And there's a special way I do that. For doing the peghead, rather than run the chance of running drips and runs down inside in this area, what I like to do is just place a little bit on there and then come in with my finger and just run it around like that.
That way, I'm getting the pores filled, but I have less of a chance of running it down inside areas where I don't want any of the epoxy.
Make sure you run your finger around the edges so you don't get any runs or drips going around the side of the peghead. Not a big deal, since I'm not done building this guitar. But if it were a finished guitar, you want to take some precautions there.
I've got epoxy, my first coat, on the entire guitar. What I'm going to do now is hang the guitar up. I'm going to let it wait overnight. Now, they say a three or four-hour cure time. Don't believe it. I like to give it at least seven, eight hours so it fully cures. Tomorrow, I'm going to come back. This is going to be day four of my class with a student. We're going to continue building the guitar, doing our fret work, finish carving the neck. At the end of the day, I'll turn the camera back on, and I'll show you how to sand and do the second coat of epoxy. See you then.
Cleaning your tools
I forgot to mention that you need to clean up your tools, and alcohol is the solvent. And the bigger the bottle, the better. I use grain alcohol in my shop because I don't like the denatured stuff. A little bit like that. And then you can just clean off your tools. They'll be ready to go for tomorrow.
Day 2: Sanding and applying the second coat of epoxy
All right. Welcome back to day two. Here's our guitar. I've now finished building the guitar. Neck is done. I've sanded it in 320. Went ahead and did my pore fill. Like I said, I don't like doing a Z-poxy pore fill on the neck because it gets into this ingrained. And to clean it all off of there, sand it all off, is a lot of sanding more than I want to do. The back and sides have one coat of pore fill. The top is now complete. It's been sanded to 320. I've masked off from my bridge location. I put a seal coat of shellac on that.
Prep for sanding
Let's start with the back. I have a few areas around the edges here that have a little bit of runs. Can come in with just a razor blade and get that. That way, I don't have as much sanding to do. I want to make my sanding as easy as possible. If I can get rid of any runs or drips, I think that's the way to go. Just take a razor blade or a scraper, and that will take care of that there.
There's just a little bit more right here in the waist. I'm going to get that. I've also masked off my neck here because I don't want the epoxy to contaminate the Spanish cedar.
Sanding
Once I get all the runs and drips off of there, I'm now going to sand it with 320 grit paper. Just to scuff sand it so the next coat of epoxy has something to bite into.
[Robert sands the back and sides using a sanding block and sandpaper]
Don't forget to do the peghead. Also, a razor blade works really well on the peghead. Keeps you from rounding over the edges. Keeping everything nice and flat.
Also, if you happen to get a little bit of residue on the side, razor blade really helps get those little runs and drips off that happen to creep over the side there. Then if you want to finish it up with some sandpaper, you can.
Keep in mind, right now I'm just scuff sanding it. I'm not taking it to bare wood, necessarily. However, I do happen to go through to the wood in some areas where it's thin. Tomorrow, we got to take it all the way back to bare wood.
If you don't like sanding, when you apply your next coat, make sure you keep it nice and clean.
[Robert sands the peghead using a sanding block and sandpaper]
Applying the second coat of epoxy to the back
Now, I think we're ready to apply a second coat of Z-poxy. All right. I'm going to mix my Z-poxy the same way I did yesterday. However, today I'm going to need a lot less of it.
You may also notice that I have changed out the newspaper on my bench. Yesterday's news is old news. I want to stay current, so I read the current news as I'm working.
Off camera, I also made sure that I sanded the bindings because you don't want any shiny areas on those. You want the epoxy to be able to have something to bite into. I also took some compressed air and made sure that I got all of the dust out of the pores. I want that Z-poxy to go into the pores. Make sure that you clean them all out. And compressed air works really well for that.
Just like yesterday, put a little bit on the back. You'll find that it goes a lot further on your second coat. Once again, I'm just using a squeegee working across the grain.
Now, what kind of finishes can you use Z-poxy as a pore fill under? Just about anything. However, you may want to put a wash coat of shellac or a barrier in there of shellac if you think you might have any compatibility issues with the product you're using as your top coat.
Keep it nice and clean because anything that's left on there you have to sand off tomorrow. Really scrape it back. I find that, if I stand up on my scraper or on my squeegee at about a 90-degree angle, you can really scrape it off well. Keep it nice thin coat on there.
Now, this stuff sands fairly easily, so don't beat yourself up if you leave a little bit on the surface in the way of a squeegee mark.
You may find also that, depending on the species of wood and how well you did your surface prep, you may want to come in and do a third coat. I find that two coats is usually enough for what I'm doing. All right. I'm going to go over to my LMI vacuum clamp now and clamp it up so I can work on the sides.
Applying the second coat of epoxy to the sides
As you're doing your sides, don't get too carried away and let it roll over onto the top. Now, the top does have a seal coat of shellac. If you happen to get any on the top, just put a little alcohol on your cloth or whatever and then wipe it on there, and it should wipe right off.
Be very careful up here in this area around where the neck comes in. You don't want to leave a lot of residue there. When I get done at the end of the session, like I showed you yesterday, I run my finger along there and get rid of any residue. Any build-up. If you get too much build-up in there, it's hard to remove your tape as well.
I know what you guys are thinking. You're thinking, "Man, how does he do that without getting it rolling over onto the top?" It's actually pretty easy to do. That is, keep it off the top. I guess if you get real sloppy with it, you could wind up getting it on the top, but I haven't really had much of that problem. I've heard about it, though. Happened to a friend of mine once.
[Robert rotates the guitar and starts applying epoxy to the other side]
All right. Wipe off the excess. Clean up your equipment, and then we're looking at a third day to sand everything back to bare wood. Don't forget to run your finger around the edge. Catch any runs or drips. Do that on the top and on the back. Also, if you want to run a finger along here ... Also, don't forget to do your peghead. I almost forgot. Don't forget to do that peghead.
Day 3: Removing the epoxy
All right. Welcome back to day three. I've allowed the epoxy to sit overnight. Did the back and sides once again. Kept it as clean as possible. I'm going to start by removing all of the epoxy. I'm going to start here on the peghead. I'm going to start with my razor blade. Scrape the majority off so I don't have as much sanding to do.
Also, like I said, it helps keep everything nice and square rather than rounding off edges.
And then once you get the majority off, you can come in with sandpaper. What I'm going to be using is 320 grit and a backing pad. And you want sand all of the epoxy off until you have nothing left except in the pores. And that means any little shiny area is a low spot. You get it all the way down so that there's no shiny area.
If you start to see some blotchiness, that means you still have ... You're sanding through your layers of your epoxy, and you want to make sure you get that all the way off. All the way back to bare wood.
I now have the peghead completely leveled. If you notice that you have any opaque areas or little cloudy dark areas, that's because you still have epoxy on there. Keep sanding to get all of that off. Now that I've got the peghead done, I'm going to go to the back and the sides, and I'm going to start with the power sander. I'm going to start with 320 grit. Then I'm going to finish everything by hand I can't get up by the neck. This area here with the power sander and the waist has a little bit of trouble, so I'm going to make sure I get all of that by hand. You want to finish by hand anyway to remove any of the marks left by the sander.
Here we go.
[Robert uses DeWalt power sander to sand the back and the sides]
I spent a few quality minutes doing some sanding with the palm sander at 320, and there's a very fine line between too aggressive and just getting it level. You don't want to sand all the way through your epoxy fill and open up more pores, but you do need to get all of the epoxy off. Next thing I'm going to do is come in by hand. I'm going to get these areas here around the heel block that I couldn't get with my sander. Also, I'm going to spend some time in the waist, and then I'm going to hit everything with 320 by hand to get rid of any of the power sanding marks. Here we go.
[Robert sands the body and sides by hand using a sanding block and sandpaper]
When I get all done sanding, I like to take a soft rag and just wipe off the majority of the dust. The rest of it I leave on there and work... I use it to my advantage. Let it work in my favor. If there's any little small pore that didn't get filled, usually that dust takes care of it. You're now ready to go over the top with your favorite top coat. Now, as a precaution, you may want to put a wash coat of shellac in there as a seal coat depending on the top coat you're going to be putting over it. But that, my friends, is how I apply a Z-poxy pore fill.
Matt in Alaska, thank you very much for that question. Like I said, that's one I get a lot about what kind of pore filler to use and how to apply it. That one was the one that I've not done yet. I've got many other videos on YouTube that show various products and methods for pore filling. But now I'm going to have one about Z-poxy as well. Thank you very much, and happy pore filling.
[on-screen text reads: More Luthier Tips and online courses available at www.obrienguitars.com. Private and small group guitar building and finishing instruction available.]
