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 have used just about every pore filling 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 sand easily. So, let’s go over to the bench and I’ll show you how I apply Z-Poxy as a pore filler.
So 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 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 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’ll also want to work in a well ventilated area or perhaps you can use a respirator. 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 backward. And one is a little heavier than the other so it’s really 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 so I’m going to put a little bit more of the amber color in there. Since they don’t mix until you mix them, you can kind of see how much of each one you have in there. And these little plastic mixing cups work really well. I just come in and stir it. Now there are several different ways to apply an epoxy. The way that I like to do it is to just put it on and then I’ll let it sit overnight, I’ll scuff sand it the next day and I 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 or other finishes that you put on. Another reason for that is when you’re sanding the second day, you’re going to go through and 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, a seal coat of shellac or something 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. So the Z-Poxy is now ready to go. I put a little bit on the surface. What I use is just a little squeegy. 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 this 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. You want to make sure that 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’m not worried about keeping it extremely clean at this point – in other words, there are not marks from my squeegy – 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 around your neighborhood, at the stores. Now, you want to be careful not to get messy and get it running down the sides and dripping. So try to avoid that. When you get enough on the back if you want to come in, if you have excess on your squeegy, just wipe 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. Alright, 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.
Now, for working on the side, I’m using my vacuum clamp 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 going ahead and starting on our pore filling 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 on 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 to avoid it so you don’t have any planer work to do later. Now the nice thing about the LMI vacuum clamp is that you can spin it around, swivel it up and down, do all kinds of things with it to make it more convenient to work with. So now I’ve swiveled over to the final side here. On day two you’re probably going to use about half as much epoxy as you use on day one. Because, like I said, the wood really soaks it up on day one. Now, when you come in and work on this area here where the neck is – I’m working on a classical guitar and I build my guitars with the neck on – make sure you don’t leave a lot of residue in there or you won’t be able to get that tape off. So, any residue gets wiped on the paper on my bench. I’ll also come in and run a finger right along there just to make sure I 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 will be a run or a drip. So you go ahead and do that on both the front and back side. If you decide to use a wood that’s porous on your peghead, don’t forget to fill that as well. There’s a special way I do that.
So for doing the peghead, rather than run the chance of running drips and runs down inside 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 of the areas where I don’t want the epoxy. Make sure you run your finger around the edges so you don’t get any runs or drips 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’d want to take some precautions there. Okay, I’ve got epoxy, my first coat on the entire guitar. What I’m going to do now is hang the guitar up, let it wait overnight. Now, they say a 3-4 hour cure time. Don’t believe it. I like to give it at least 7-8 hours so it fully cures. Tomorrow I’m going to come back – this is going to be day four of my class with the student. We’re going to finish 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. 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. So a little bit like that and you can just clean off your tools. They’ll be ready to go for tomorrow.
Alright, welcome back to day two. Here’s our guitar. I’ve now finished building the guitar. The neck is done, I’ve sanded it to 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 end grain and to clean it all off there, sand it all off is a lot of sanding. More than I want to do. So the back and sides have one coat of pore fill. The top is now complete. It’s been sanded to 320, I’ve masked of my bridge location and I’ve put a seal coat of shellac on that. So let’s start with the back. I have a few areas around the edges here that have a little bit of runs. You 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 so get rid of any runs or drips. I think that’s the way to go. Just with a razor blade or a scraper and that will take care of that for you. There’s just a little more here in the waist. I’ve also masked off my neck here because I don’t want the epoxy to contaminate the Spanish Cedar. So once I get all the runs and drips off 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 bind to. Don’t forget to do the peghead. Also, a razor blade works real well on the peghead. Keeps you from rounding over those edges. Keep everything nice and flat. Also, if you happen to get a little residue on the side, a 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 up with some sandpaper you can. Keep in mind I’m scuff sanding it. I’m not taking it to bare wood necessarily. However, I do happen to go through the wood in some areas where it’s thin. Tomorrow we’ve 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. Okay, now I think we’re ready to apply a second coat of Z-Poxy.
Okay, 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 have something to bite into. I also took some compressed air and made sure that I got all the dust out of those pores. I want that Z-Poxy to go into the pores so make sure you clean them all out. And compressed air works really well for that. Okay, so just like yesterday – a little bit on that back. You’ll find that it goes a lot further on your second coat. Once again I’m just using a squeegy, 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 of shellac if you think you might have any compatibility issues with the product your using as your top coat. Keep it nice and clean because anything that’s left on there, you have to sand off tomorrow so really scrape it back. I find that if I stand up on my squeegy at about a 90 degree angle, you can really scrape it off well. Keep it a nice and thin coat. 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 squeegy 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. Alright, I’ll go over to my LMI vacuum clamp now and clamp it up so that I can work on the sides. So as you’re doing your sides, don’t get too carried away and let it roll over onto the top. The top does have a seal coat of shellac so if you happen to get any on the top, just put a little alcohol on your cloth or whatever and then wipe it right off. Be very careful up in this area, where the neck comes in. You don’t want to leave a lot of residue in there. When I get done at the end of the session, like I showed you yesterday I run my finger along there to get rid of any residue, any buildup. If you get too much buildup 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 around over the top?” It’s actually pretty easy to do. I guess if you get real sloppy with it you could wind up getting it on the top. I’ve never really had much of that problem. I’ve heard about it though. It happened to a friend of mine once. Alrighty. 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 the back. So 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 your peghead.
Alright, 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 the epoxy – I’m going to start on my peghead with my razor blade. I 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 round off the edges. Then once you get the majority off, come in with sandpaper. What I’m going to be using is 320 grit and a backing pad. You want to sand all of the epoxy off so you have nothing left except for what’s in the pores. That means any little shiny area is a low spot. We’ll go all the way down so there are no shiny areas. If you start to see some blotchiness, that means you’re sanding through your layers of 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 so keep sanding until you’ve got all that off. Now that I’ve got the peghead done, I’m going to go to the back and sides. I’m going to start with the power sander. I’m going to start with 320 grit and then I’m going to finish everything by hand. I can’t get up by the neck, this area here with a power sander. And the waist has a little bit of trouble. So you want to make sure you get all of that by hand. You want to finish by hand anyway to remove any of the marks left by the sander. So here we go. So I’ve 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 and open up more pores but you do need to get all the epoxy off. The 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 at the waist and then I’m going to hit everything with 320 by hand to get rid of any of the power sanding marks. So here we go. When I get all done sanding, I like to take a soft rag and wipe off a majority of the dust. The rest of it I leave on there and 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 on 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 filler.
So 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. So that was one that I had not done yet. I’ve got many videos on YouTube that show various methods and products for pore filling but now I’m going to have one about Z-Poxy as well. So thank you very much and happy pore filling.