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
Question
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.
AI enhanced answer (added Jan 20, 2025):Here are some effective methods to fill gaps in wood using sawdust mixtures:
1.
Sawdust and Wood Glue: Mix fine sawdust with wood glue until you achieve a consistency similar to peanut butter. This mixture can be pressed into gaps, dries hard, and can be sanded smooth. It's ideal for small to medium gaps and blends well with the wood.
2.
Epoxy and Sawdust: Combine epoxy resin with sawdust for a stronger fill, especially useful for larger gaps or where structural integrity is needed. The epoxy hardens, providing a durable repair. You can tint the epoxy with wood stain to match the color.
3.
Sawdust and Lacquer: For a quick fix, mix sawdust with lacquer or shellac. This dries very quickly, making it suitable for small, cosmetic repairs. However, it's not as strong as glue or epoxy.
4. **Sawdust and CA Glue (Super Glue)**: This method is excellent for very fine gaps. The CA glue sets almost instantly, and the sawdust helps in color matching.
5.
Sawdust and Polyurethane: Mix sawdust with polyurethane for a flexible fill that can expand slightly, useful for gaps that might move or expand with temperature changes.
When using these mixtures, ensure the sawdust is from the same or similar wood to maintain color consistency. After filling, allow the mixture to dry, then sand it down to blend with the surrounding wood. Remember, the choice of filler depends on the size of the gap, the type of wood, and the intended use of the piece.
