Filling knots with colored epoxy usually works quite well, but sometimes the void is in a spot that’s difficult to fill, like the edge of a board.
Here’s how to do it. First, apply some paste wax to a piece of melamine so the epoxy won’t adhere to it. Clamp the melamine to the workpiece, creating a well.
Thoroughly mix the epoxy, then add tempera powder. Start with about a 1:1 ratio of epoxy to powder. You can use powder of any color (a wide assortment is available at craft or hobby stores); black generally looks the most natural. I use slow-setting epoxy because it gives me more time for mixing in the powder, but 5-minute epoxy will work.
Fill the well with the epoxy until it just starts to overflow. If you don’t overfill, you’ll have to add more epoxy later, because the glue usually soaks into the wood a little bit. Slice away the excess epoxy with a chisel before it fully hardens. Sand it smooth when it’s cured. –Richard Helgeson
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