Expert: Jamie Yocono - 4/12/2009

Question
I'm building a mantel out of knotty alder & would like to know what would be the best material to fill the nail holes, so it would blend in with the wood & be stainable?  Also what should I use to fill the knot holes?

Answer
Hi Mike,

I've seen a lot of discussion about what makes the best filler for knot holes, but I'll tell you what I think works best. First, there are two ways to approach filling them - you can do it before the wood is finished, or you can wait until after the finish is applied. There are pros and cons to both ways.

If you use a commercial filler, there is a good chance that the spot isn't going to match the rest of the wood. Filler won't accept the wood finish the same way the wood does, so it's bound to look different. Plus, you probably won't find a specific "alder" filler. More likely, you'll find some generic colors, like pine (a light color), cherry (a reddish color) or walnut (a dark brown color) and while one of these may get "close" to your alder, it's not going to be an exact match.

Another thing to consider is what type of finish you're using. Varnish? Lacquer? Oil? The finish you're using is important when choosing a filler.  Some people mix some of the wood's sawdust with glue, and then use that mix to fill the voids. But glue doesn't finish well at all. So that is a terrible idea! Don't let anyone talk you into a glue/sawdust mix.

I prefer to fill holes in one of two ways. Yes, I use the sawdust, but I mix it with the finish I'm using. So if I'm oiling the wood, I will mix some fine sawdust (taken out of my sander bag) with some of the oil. Make a putty out of it, and apply it to the hole. Rub it smooth, then apply oil to the rest of the wood. It will match better than anything you can buy.

In your case, I would mix the sawdust with a little stain, so that it will match the piece. Then add a little of the finish you're using, maybe polyurethane? Make a putty out of it.

Another method I use is with a putty stick or a crayon. Finish your wood as normal, and after that last coat is dry, try to find a putty stick (in the paint department of a hardware store) to match the color of the finished wood. If you can't find anything that works, check out a box of crayons. Some of those big boxes have many shades or browns/tans/reds/beiges that will work. It's not a perfect answer, but it will at least match better than anything you can buy.

I like the sawdust idea best, but you have to mix it with the same type of finish that you'll be using. It's not perfect, but it will get you really close to the perfect match.

Good luck, write back if you need more help.

Jamie Yocono
Wood It Is! Custom Cabinetry
Las Vegas, NV
www.wooditis.com