Filling Gaps with Sawdust Mixes

The old "mix sawdust with glue" trick takes a beating here from skeptics — but there are other suggestions. October 1, 2010

What glue or varnish could be mixed with walnut sawdust in order to fill large cracks in walnut? The goal is to have the varnished or oiled finished piece not look darker or lighter at the site of the filled hole.

Forum Responses
(Finishing Forum)
From contributor A:
The glue sawdust method never works well in my opinion. The difference in appearance of coated endgrain versus facegrain is obvious. Sawdust is saturated wood fiber, 75% of which has some or all endgrain showing. That is why the wood dust/glue always appears darker than the face or side grain that is being filled.

From contributor J:
How dark it takes a finish depends on how much glue you use. You will need to experiment with different ratios. I would use original tight bond diluted with some water. I have had it work well and I have also as Contributor A stated had it turn way too dark. Why are you using wood with large cracks in it? Your answer may be tinted epoxy if they are large enough.

From contributor I:
Forget the glue and sawdust. Take the touch-up approach. That’s what we do every day. You’re not going to get grain lines and background colors without it. If you must use sawdust then use the same stain that you finish with mixed into your glue. I like to do that with all my regular glue joints and especially laminations. The glue joints just disappear.

From contributor W:
Yes forget about sawdust. You have to touch up your gap. For small gaps you can use a putty for fill. Then touch up your finishing to get the color match. For the big gap, it is better if you use a wood piece to fill in your gap.

From contributor O:
I recently read somewhere, and recently tried a different method with better results than the glue/sawdust method. Use the finest sawdust you can get, such as from a sander, and mix it with shellac. I have used this method several times now with better results. I now have small canisters saved of the different species sanding sawdust saved. I used seal cote as my mixing shellac.