Email This Page to a FriendHow to Use Epoxy, Part 1 – Coating Plywood for Paint or Varnish
March 24, 2016
For your next project, let Eric Blake walk you through using an epoxy buildup coat before painting or varnishing bare plywood.
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– [Voiceover] Epoxies are known to be used for bonding wood together, gluing wood together, but it can also be used for coating surfaces. In this video series, we brought you to the Brooklyn boat yard where we use epoxy every day to build high end boats.
– I’m gonna show you the best tips, and trips we learned over the years in using epoxy to clear coat a surface for paint and varnish, and how to use epoxy with fiberglass cloth and dynel to get perfect decks and cabin tops. Let’s start with how to clear coat epoxy and create a beautiful, smooth and water poof surface for surfaces that are going to be painted or varnished.
– Some things you may want to have – The roller that we use for epoxy work in the boat yard. It’s a very thin nap foam roller. The thicker these gets, the more glue and the more mesh you tend to make. So for finishing epoxy clear, we use something like this. These come in seven inch that you would put on a typical roller cage, but this is just a small three inch. Just a stock three inch foam brush for tipping out, and also a chip brush, which we’ll talk about, the use for tipping with something like that. We use primarily West System Epoxy in the shop. We always have. And your typical basic epoxy, whether it’s, um, many companies have typically a fast cure, a slow cure, and then some kind of a special clear coating to style epoxy. And I want to show the benefits of both. We have these metered pumps that as you open the valve and crank them out, it’s already metered at the proper ratio. Epoxy can be mixed by volume, using your basic painter’s cup, whether it’s five to one mix ratio, which is what the West System fast is, or three to one, you want to be very clear of your ratio. All epoxies are different and mixing them by volume in a cup like that so long as you stick to the resin and hardener ratio, you won’t have a problem. We use such large quantities of this that we have these kind of metered pumps. You walk up, you throw the valve open, you take what you need, you walk away, you don’t think about it. A pair of gloves is always key. Let’s start with the West System fast. This is their stock fastest cure time epoxy. Basically when you’re clear coating and rolling and tipping, you want to be able to put as many coats as you can on to build up a thickness if you’re painting it. If you’re varnishing it, typically, you’d only want two coats so it doesn’t get murky. But fast enables you on a painted surface to apply, one over the other, over a period of time, up to four coats over the course of an eight hour day, which is a nice thick build up that gives you the ability to sand that out and have an epoxy sealed surface. One thing with the 205, over time, the hardener gets a real red color, which is an amber that is going to change the tone of your wood, something to be aware of. The 207, which is the epoxy that West System sells for clear coating, is a different ratio. It’s three to one. When it comes out, it is very clear. There’s a very, very slight amber resin, but nothing at all like the 205. It’s also a much thinner epoxy than the 205. The 205 is a little bit thicker in consistency but both are used for what we’re about to do. So let’s get back over to our panel and have a look. We’re gonna start with the 205, and we’ll just do one small panel of that to give us a comparison. You want to mix this very thoroughly. I’d say a couple of minutes of mixing. The whole idea is that you’re building a surface here that is going to fill the grain and give you a paintable surface that is sealed from moisture. A big mistake that I see guys make is that they dip their roller in, and they’ve got a lot more glue on some parts of the roller than the others. When you go to roll that on, that’s how it comes off the roller. If you look at that, these areas are coated with a very thick layer and these have none. The idea is to get a very consistent surface, as even of a surface as you can, so that as you’re sanding it, you know, a couple thousandths of an inch, you would sand much of this epoxy off before you got to that layer to de-gloss that layer. So the idea is whenever we’re coating is to use these ribs in the paint tray to get as even of a coat on that roller as possible, and then to work that as evenly as you can. You see the difference there between what I just did by really thoroughly getting the epoxy on the foam roller. Typically, I will roll one direction and then the other. You can see the color of this epoxy really changes the tone of the wood. Again, it may be something you’re after. If it’s a painted surface, it doesn’t matter and it allows you to get more coats on in a day using the fast than the 207. Typically, anything that is going to be painted, we would roll and coat with epoxy, primer and then paint would go over that. It gives the wood a complete barrier. If something is going to be finished right, typically, we only epoxy coat wood that is going to be finished with a two part automotive style finish. If something is going to be finished with varnish, while you can varnish over clear coated epoxy, it is a very, very difficult thing to maintain the longevity of that going down the road. To block out varnish. In 10 years, varnish really should be stripped, and then not only are you stripping varnish, but you’re having to strip back through that epoxy, sanding out all that epoxy, which is a much more difficult thing to do than just heat gunning and scraping back varnish. Epoxy clear coating is a very durable surface, and what is actually required of a two part automotive clear varnish, but not something I would necessarily recommend to be put on and varnished over with a single part varnish. And another place you see epoxy clear coating overused is on solid wood joinery. Solid wood has the ability to come and go. It moves, there’s no stopping it. And an epoxy coating is a very, very, not incredibly flexible sealer. Epoxy coating would be used on something that is plywood based construction that may be veneered inside and out so it has the appearance of traditional joinery, but is very much a monocoque structure. Now let’s go to our 207. Again, this is epoxy that is sold as a clear coating epoxy. It’s thinner, it’s not as viscos. It is very much a clear finish unlike the 205. And again, applied much the same way. Roll. You see I’m getting as much on the surface as I can and as evenly as I can. I’m going 90 degrees to the grain, and then cross grain. And what I want to demonstrate here is what it is like to leave something as evenly put on as you can by a roller alone, and then something that is rolled and tipped. We can do that right next to this, and once the epoxy is set up, we can sand those out and have a look at the differences. That is about as even I can get something put on with a roller. Again I applied 90 degrees to the grain, went with the grain, and then finished 90 degrees to the grain. The next thing I’d like to demonstrate is a rolled and tipped epoxy coating. Again, this is something you’re going to varnish and you want to get on as evenly as possible so as you sand it, you’re not burning through. Epoxy can be overworked and when you overwork epoxy, you introduce air to it and it almost muddies the surface. Gives you kind of a slight murky look, and I can demonstrate that here. I am working that epoxy way more than you would need to and you can see that eventually, it gets a milky, a milky look. Sometimes that will eventually work itself out as the epoxy sets up, but something you want to avoid. Basically, just apply it as evenly as you can. Once we’ve applied as evenly as we can, and I will dip a little bit with that foam brush, and with the grain, much like varnish, I am tipping in the direction of the grain of the wood. That just levels out that texture again that’s left by the roller. Okay, and you can overwork it. Typically, on smaller parts, I will use a foam brush. On larger areas, like varnish, you would roll a section just maybe two feet wide, tip that out, move over, roll another section out, and overlap your tipping, just like varnish. Many thin coats is better than one or two very thick coats, especially when you’re getting into finishing something bright. Another thing that I wanted to show you was if you’re using a chip brush to tip epoxy out, not all chip brushes are created equal. While these are both throw away disposable type brushes, this is kind of your “el cheapo” version of a chip brush. Use one of in epoxy, because of the viscosity of the epoxy you’re gonna lose about one third of those bristles. They’re just a very cheap throw away brush. While this may be a three dollar brush, this may be four dollars and 50 cents. They’re called a fooler, and this is what I use for any kind of tipping in varnish buildup or epoxy, a much higher quality disposable tip brush. Chances are, with epoxy, with varnish, it’s going to pull a bristle out of the brush. You can see there’s a bristle right there. The time to get that bristle out is right now, and how you do that is by stabbing, by stabbing and grabbing it out and then tipping back through that area. Leaving bristles in your finish is something that you just have to sand out if it’s gonna be finished clear, if that bristle is across the grain, it’s something that in close inspection, you’ll see that. So you want to use a high quality brush if you are going to tip. And the time to get those bristles out is as soon as you see them. Epoxy, like varnish, once you actually coat something and five minutes later, you go back and you say, “oh man, there’s a bristle there.” It’s not the time to go after it. You’ll make more of a mess and more of a crater trying to get that bristle out than if you do it straightaway. So after 10 or 15 minutes, it’s too late. I would say just forget about it and walk away. A bristle right there, and again, you just quickly stab it with your brush, and then brush through it. Typically, to put successive coats on, you have to wait until the epoxy is called B-stage, which is not fully cured, but in the curing phases, and the 205 will reach that point faster than the 207. We’re gonna let these sit and come back and I’ll show you guys the optimum time to put a second coat on these. So for demonstration purposes, I just use this little three inch foam roller. Any hardware store carries this kind of thing. You really want to stay away from anything with a nap or a hair. Invariably that comes off in your finish and gives you a much more textured finish than you’re after. On anything larger, I would move to a seven inch version of this that goes on a conventional paint roller. Just to kinda give you a look at the different tools you may run into. So we’ve just come back to our panel and the fast 205 is tacky, but not necessarily coming off on your glove and that is the perfect time to re-coat and it’s what’s called B-staged. That’s gonna happen a lot faster with the 205 than the 207. Typically we only get two coats of 207 on in a day, the clear coating epoxy. 205 – again, on a painted surface, something you’re not worried about the petin changing the color, and you want a nice thick build up, you could get three, if not four coats of epoxy, rolled on this over the course of the day if you catch it at the right time. Now’s the right time to apply a second coat. So again, you want to get the roller nice and even, and do as neat of a job as you can, rolling. You can feel the epoxy coming off the roller, if it chunk, chunk, chunks, that means that you have thick and thin spots on your roller. You really want to work that out into a nice even sheen without overworking the epoxy and introducing air that’s going to make it opaque. Not as big of deal on something that’s gonna be painted, but certainly a big deal on something you want to varnish later. We’re gonna tip that out with a three inch foam brush. Nice even strokes. This 207 is more primed to be top coated. I’m going to apply epoxy to this like I’ve seen epoxy applied a lot, which is just kind of haphazardly and not in a very neat way. Kind of to demonstrate the importance of putting on an incredibly even layer, and then tipping it out with a brush, and that’ll become evident as we start to sand that. Our second panel here where we’re rolling and tipping. Nice even layer. I’m going to tip that with the grain. That’ll help show the differences and the importance of applying it as evenly as possible. Next in the series, we’ll talk through sanding these out and getting a nice, smooth paint or varnished surface.
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