Using a Hot Glue Gun to Fill Wood

In a couple of my latest videos I showed a little snippet of filling voids with a hot glue gun. And, while I was quick to gloss over it, many viewers asked what in the heck I was doing with a hot glue gun on the fancy wood. The short answer is filling voids, mostly from knots, but also from cracks and any other imperfections which show up naturally while processing solid wood.

We started using the system (we purchased it from Rangate) about a year ago, and it has won us over in the shop for its speed, while producing great results. It has been taking over for epoxy in more and more situations as we gain more confidence in its ability to perform.

The knot filler sticks are basically hot glue sticks and we call them hot glue sticks. However, they are definitely different. I can tell you from experience that actual hot glue sticks aren’t sandable like the knot filler sticks made to fill wood. I attribute it to a lower melting temperature of the hot glue sticks, which almost immediately gum up sandpaper and just get pushed around on the surface like old chewing gum. YOU HAVE TO USE KNOT FILLER STICKS.

We have been using the sticks purchased from Knottec because they are more reasonably priced than the options from Rangate and seem to work equally well. Overall, I feel like the Rangate system is overpriced based on the fact that in the end it is really just a 300 watt hot glue gun and a couple of simple accessories, which are available for much less money than we paid.

The knot filler sticks are available in several different colors, but we mostly use black. It seems to look the best in almost all occasions. Only on white woods, like maple, do we deviate from the black, but there are many times even in those white woods, where the black looks great. If you only get one color, get black.

Overall, using the hot glue gun is super simple. Just squirt some in the defect, squish it in with an aluminum block (which also quickly cools the glue), and then cut off the extra. Click the video below to see just how quick and easy it is.

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About wunderwoods

Hi! My name is Scott Wunder and I am the owner of WunderWoods Custom Woodworking. We build wine cellars, built-ins and furniture from local woods, here in St. Louis, MO. Recently, I finished a three-year term as the President of the St. Louis Woodworkers Guild, which had me writing a monthly article for our newsletter. I love to write, especially about wood, and found that I still had more to say. Every day I run into something wood related that I realize some of my customers don't know and this seems like a great forum for sharing what I have learned (instead of telling the same story to each person). The main thing to remember is that I try to keep it light and as my wife always reminds people that have just met me, "He is joking."

3 responses to “Using a Hot Glue Gun to Fill Wood”

  1. Rick Thaler says :

    I have been experimenting with the Knottec brand epoxy hot melt since I first noticed it in your blog. It’s great for cracks and pin knots but so far I’ve been unable to get a decent looking surface on larger fills. Is the aluminum pressure block essential in getting a hard final surface to sand?

    • wunderwoods says :

      I don’t think the aluminum block affects the final surface. On larger fills (especially ones that I add bark) I usually leave it high and don’t use the block. The next step for me is to go to the wide belt sander, which will sand a large area faster. I’m guessing that you are running into issues with large fills getting hot and, in turn, soft from a focused sanding effort with a hand sander in one area. Try to remove the material quickly, without creating too much heat. A plane or rasp or even a rougher grit belt sander will speed up the material removal and create less heat. I often finish sand the larger areas by hand, with a stiff sanding block backer to keep everything flat. If you do this, it will also reduce the heat.

  2. Brian Keith Ellison says :

    Great Video Scott, thanks a lot!

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