There are many ways to create a smooth finish on wood, but one of the easiest is to use grain filler. In this video, Rob Johnstone demonstrates how to apply grain filler to create a smoother board surface.
Grain filler is a paste that fills the open pores and grain in a piece of wood. The grain filler is applied across the wood surface with a card or scraper. The excess on the surface is scraped off, leaving the filler down in the open grain and pours. It typically takes several coats of grain filler to completely fill the pours, leaving them flush with the top surface of the board. If you want to create a glassy smooth surface, the kind you see on many guitars or pianos, then you'll need to also do several additional steps of applying finish coats, wet sanding and buffing.
Video: Creating a Smooth Finish with Grain Filler - Video Transcript
Rob Johnstone: A common question I get from woodworkers is, "How do I get a super smooth, super shiny finish?" Like a lot of woodworking questions, there's more than one answer to it but I'm going to demonstrate what I think is the easiest way, so let's get started. Hi, I'm Rob Johnstone and years ago when I was in school to learn how to build and repair stringed instruments we used to joke about how guitar owners like their guitars to be as shiny as plastic, but truth be told a lot of woodworkers feel the same way.
To be perceived as shiny, one of the characteristics of the finish is that it must reflect light evenly. To do that the finish needs to be even. The first thing you need to do in order to get a super shiny finish is you guessed it, sand it, very smooth. Close-grained wood is easier to finish this way as it has smaller pores in the wood. Why is that important? Because pores are little holes in the wood fibers and clear finish will sink into the pores keeping the finish from being smooth and even. Now if the surface is sanded smoothly, go ahead and apply a light coat of finish or sanding sealer, I prefer shellac. That's all it takes.
I'm going to demonstrate the trick that will make achieving a super smooth finish so much easier, applying pore filler. Pore filler does exactly what its name implies, it fills up the little pores in the wood so that they're even to the wood fibers. It's easy to apply. I use an old credit card or the like and just squeegee the filler into the wood grain. First, with the grain then across the grain, then let it dry according to the directions on the can. In almost every case it'll take multiple applications of the pore filler in order to get a really smooth surface. I like to examine it by holding it up and getting a low light raking across the surface. Much like your shampoo where you rinse and repeat, with this, we're going to sand lightly and then repeat. It'll take at least three coats of the pore filler I think in this particular piece of wood before I'm going to be happy with a nice smooth finish. When I am, that's when I start to apply the topcoat.
Now, I prepared a piece in advance so that I can demonstrate to you the difference between a side that has pore filler applied and a side with no pore filler. Here, I'm applying a coat of shellac from an aerosol can. I want the surface to look completely wet. I'm guessing you might even see the difference with the first coat. Now, I can almost hear some of you clever woodworkers out there saying that, "Hey, that wasn't a close-grained hardwood." And you're right, it's planes on ash, it's one of the most open grain hardwoods you can get. I actually did that on purpose to demonstrate the dramatic difference that pore filler can make. I didn't actually say you can't use pore filler to get a super smooth finish on open-grained wood, just that close-grained wood is a lot easier. Pore filler is easy to use and it's really helpful when you're trying to get a super smooth finish. To get something as shiny as plastic like in this guitar there's a lot more steps, there's many coats of finish, there's wet sanding and then there's letting the finish cure and buffing it out, but if you're just looking for a smooth shiny finish, pore filler will get you there without a doubt. I'm Rob Johnstone, thanks for watching.
