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Now and then when turning I get holes and voids in my project. The pictures below had a branch going through the blank and popped out leaving a large hole to deal with. The hole is ~1" in diameter.

I've seen people use epoxy and other products to fill these up and sometimes sprinkle colors in them to make them stand out.

My question, what products are available for this type of filler. They would need to be soft enough to not damage turning tools since I would need to finish turning the bowl afterword. It should also be food safe. And it would be nice to be easy to work with. So what are my options?

[Bowl with hole Bottom

  • Honestly, I would go with epoxy. It's pretty easy on turning tools, and food safe enough once cured. Plus, it polishes well. – grfrazee Apr 8 '16 at 21:14
  • @grfrazee are there any kinds of epoxy that would be better or more useful than others? – bowlturner Apr 8 '16 at 21:17
  • I really can't say. I normally buy whatever is available at the hardware store. Slow-set is better since it has more time to flow into the crevases of the hole. You can also tint the epoxy with dye. – grfrazee Apr 8 '16 at 21:19
  • One of the most interesting ones I have seen is epoxy with brash shavings mixed in. When smoothed, sanded and finished it sparkles just a little bit.. – Ashlar Apr 9 '16 at 0:44
  • I updated the tag to something that has been more widely used. Feel free to change it though. Perhaps we could use a synonym for foodsafe or food-safe – Matt Apr 9 '16 at 2:38
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I would use filled epoxy for this, it's probably the best thing going as it's very tough, bonds very firmly to the wood and can be extremely cheap. Possibly best of all you make as much as you need when you need it without any worries of buying more of a product than a single project needs and having the rest go off sitting on the shelf

Once fully set epoxy fills respond very well to working with sharp tools and in should sand excellently too (although it can end up very hard, much harder than the surrounding wood).

You can use any type of epoxy, from the cheap stuff in the dollar store to an expensive 'epoxy system' such as those sold by West Systems and others. They all seem to work about as well. When doing a large fill a longer setting time can be advantageous — especially in warm weather! — but even for a fill of this size I've used 5-minute epoxy and had plenty of time.

Speaking informally when this is recommended people usually just say to use sawdust, and literally sawing dust mixed with epoxy can actually work fine even though it can be relatively coarse. But if you want a very smooth finish and a more uniform colour use the finest dust you have available.

In boatbuilding where filled epoxy is used widely as a construction material it's not uncommon to buy commercial wood flour for this purpose, but sanding dusts from an ROS are generally fine and work about as well, especially if created from paper finer than 180. I've had pretty good results using the dust from a worn 80-grit belt so you don't have to be too fussy about this though!

Method
Blend the epoxy together first, to ensure it is properly mixed, then mix in the dust.

You can mix in just enough dust to colour, the often-cited "peanut butter" texture (literally looks like peanut butter if the wood dust is the right colour) or much denser than this, a paste stiffer than spackle/patching plaster. They all work fine in the right context, what'll suit best is partly up to you and partly dependent on the nature of the void being filled.

For a through-hole like this, using a mix of any sort of liquid consistency you'll want to back the hole with tape to stop it simply running out the other side of the hole. Masking tape or painter's tape are usually used but plastic packing tape also works excellently.

Other fillers and colouring agents
To colour only:

  • oil paint
  • enamel paint
  • dry pigment (glow-in-the-dark powders are currently quite popular)
  • alcohol-based wood dyes

Be cautious about adding too much of any of these or you'll severely compromise the strength of the epoxy.

Tinted epoxy looks great but in general you'll get a stronger fill when you fill the epoxy with some type of dry dust. Nearly anything can work:

  • sawdust
  • sanding dust
  • wood flour
  • metal powders
  • talc (also used as an additive, to improve sandability as it's very soft and lubricant)
  • microballoons
  • fumed silica (also used just as a thickener)
  • plaster of Paris or other types of dry plaster
  • crushed stones (turquoise is currently very popular)
  • coffee grounds (my preference is used, and very thoroughly dried)
  • wheat flour
  • cornstarch

Those last few are not jokes!

I happened to be reading this just yesterday, using epoxy and coffee grounds to fill voids on turned bowls, on Doc Green's Woodturning Site.

Note this from the above link:

Generally speaking, I wait at least two hours before I attempt to sand the filled area. A delay of four hours is better; and overnight is better still.


It should also be food safe.

This is a contentious issue in woodworking circles. What one person considers food-safe another will not, a great example being thinned varnish (some versions of "salad bowl finish" are just this) which some refuse to use even for the stated purpose, but which others are comfortable to use on a cutting board.

The nature of the food contact can be considered an important factor as well, what's OK for incidental food contact (such as you'd get on a kitchen table) is not necessarily the same as with a food-preparation surface where raw food will routinely be in contact with it.

As a general rule, any finish that dries/cured hard can be considered food safe once fully dried or cured. Any toxic ingredients (and there can be some, usually in minute quantities) are safely locked away in the matrix of the hardened finish. This includes heavy-metal driers in some wood finishes, e.g. BLO and varnishes.

Now what about epoxy? With wet starting products are most definitely not safe, at the least they are irritants and you do want to be careful to clean off any accidental contact when using it. But once properly mixed and fully cured epoxy is generally believed to be utterly safe, safe enough that it can be used to coat wooden drinking vessels.

So I think it's perfectly fine for something like this myself but your mileage may vary.

  • Awesome answer. It's great to hear from those who have used this stuff – bowlturner Apr 9 '16 at 12:19
  • Well, this was gonna be my answer, but you expanded upon it much more than I would. Very nice. – grfrazee Apr 9 '16 at 13:53
  • @Graphus How much wood dust do you need to achieve various consistencies? Asking because I'm curious how much dust I'd need to make/have on hand before mixing the epoxy. I realize it depends on how much epoxy you're making, but even a general idea would help. – Charlie Kilian Aug 14 '17 at 21:26
  • @CharlieKilian I can't really give you a good idea verbally I'm afraid. Also it is highly variable because the fluidity of the epoxy plays a part and some are more watery than others, and also the fineness of the powder is a factor (finer powders give thicker mixtures broadly speaking because there's a larger surface area), I think your best bet is to look at some of the pictorial guides online which show a mix being done, then run a few small-scale experiments with the materials you'll be using. [contd] – Graphus Aug 15 '17 at 6:14
  • @CharlieKilian Just as a general guide to how to mix I would keep the powder off to one side, fully blend the epoxy and then add the powder to the epoxy bit by bit until you hit your target consistency. That's the only way to be sure you don't overshoot the mark and get something thicker than you need, which is unfortunately surprisingly easy to do if you're only making small amounts. But the good news is that if you're using a slow-setting epoxy you can reduce its viscosity by heating with a hairdryer, making a too-stiff mixture much more pliant and easy to place. – Graphus Aug 15 '17 at 6:17

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