How Do You Fill Knots In Wood?

If you’re asking yourself how do you fill knots in wood? Then you came to the right place. Stick around and I’ll show you a method I’ve used for years. This is a method that doesn’t involve epoxy, I do use epoxy a lot as well.

Today we will be dealing strictly with black walnut. Now this is the method I have used for years. It doesn’t mean it’s the best method out there, but it has worked for me without fail and I love the color we end up with. If you’ve worked with black walnut much, you’ve probably noticed more and more knot holes showing up. Unless you want to pay an arm and leg for a better grade (which in my area still has knots) then we need to make those knot holes shine. Let’s get started.

Here are the tools and supplies you will need. How Do You Fill Knots





Not bad so far right? You can do this! So, let us take a look at our victim.

Knot Hole









I had a lot of knots to fill so I mixed approximately 5 scoops of Durham’s Rock Hard with my putty knife and 1 good scoop of black powder dye.


Durhams Pre Dye










When you mix the dye in with your Durham’s it should look similar to the color I have here. Much like charcoal ash.

Mixed Powder Filler










Now, you want to slowly add small amounts of water, stir, add water, stir, add water. Careful, it will get really watery faster than you imagine. If that happens you can just add a bit more Durham’s. I like to have my mixture about the consistency of pudding. Just runny enough to fall off the stick in lumps, not runny enough that it streams or quickly drips off of the stir stick. If you mix it too thick you will need to work quickly because the Durham’s will set up fast and you will have to beat a hockey puck out of your mixing cup. If I am filling only several holes, I mix it thick. If I am filling a dozen, I will mix it thin.

With your water added, the putty should now be a nice dark black.

Mixed Filler










Grab a scoop with your putty knife and force it into the knot hole. I press then scrape excess, press then scrape, then I leave a very small build up over the knot hole. This stuff gets rock hard so don’t leave a big mound you could launch a motorcycle off of or you will be sanding a long time.

Filled Knot Hole










You can see it start to dry as it turns more grey in color. Don’t panic though, your finish, stain, lacquer, or poly will darken it back to a nice color that matches walnut knots. Now, I should probably mention, I sand my walnut to 150 grit sandpaper before I fill the knot holes. I fill the knots and when they dry I sand them with the same 150 grit paper. If you read my blog on sanding with a random orbit then you know I will follow up with 220. Then once again with 220 grit sand paper by hand with a flat block.

sanded Knots










There it is, now if someone asks you how do you fill knots in wood? You can show them with confidence. This is just one method, I sometimes use a 2 part epoxy instead.

Have a method you like? Please feel free to comment and share your knowledge.

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