I’m new to live edge woodworking. I am finishing a walnut slab for a kitchen table that has some minor defects such as small cracks and knotty areas. I would like to fill those with epoxy. But unsure of the steps I need to do this in. I want to tung oil the slab and have a ending overall finish of a hand rubbed poly. Not sure if all of these materials will work together or the order and process that I should do them in. Any info would be of great help. Thank you
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2Did you check previous Q&A for epoxy? woodworking.stackexchange.com/search?q=epoxy– user5572Nov 26, 2021 at 22:04
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1Why use tung oil? Boiled linseed is much better!– Volfram KNov 27, 2021 at 9:32
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1Could you add a couple of photos of the piece of walnut you're using so we can see what you're dealing with?– GraphusNov 30, 2021 at 13:47
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2 Answers
Many "live edge" slabs/boards have structural issues like voids, knots, cracks, etc. which can be filled using two-part epoxy. To prepare the surface, sand with coarse grit sandpaper to remove dirt, debris, etc. and to expose any hidden defects and so on.
Because most large defects generally extend to the opposite side of the slab, you will have to cover the opposite side of the defect to contain the epoxy. Sticky tape, like duct tape, masking tape (maybe more than one layer) or similar should hold the epoxy in place until it sets.
Mix the epoxy of your choice in a quantity to fill the defect(s). It's generally better to mix up a little more than you need than to come up short and have to mix up another batch. Ideally, you want to do it all in one "pour" when possible.
When you mix up the epoxy you can also tint it with dyes or acrylics to help it blend in with the wood. The color choice is up to your personal preference, but people often use black epoxy because it tends to blend in better than big clear areas, but you can do any color of the rainbow, if that's what you want.
You should be aware of the "open time" of the epoxy. This refers to the time it takes for the epoxy to start to firm up and lose it's liquidity. This is typically anywhere from 5 to 60 minutes. You want the epoxy to be as liquid as possible to make it easier to get into the voids. For large voids (or a large number of voids) you'll want a longer open time to allow you to fill all the holes without having to hurry, but for smaller voids (or a small number) you can get away with shorter open times.
There are gazillions of sources for complete tutorials and how-tos for detailed steps for filling voids in wood using epoxy. A lot are about making fake rivers and lava flows in table tops. Most of them are good enough to get you through the process. Here is one.
Once you've filled the knots, defects and miscellaneous voids, you'll want to machine the slab flat. That could entail sanding or planing depending on the condition of your slab, the tools you have available, and your personal skill set. In any case, the goal is to smooth out the slab so that not only the wood, but also the epoxy is one smooth plane.
Once that is accomplished, you'll want to sand the surface of the wood using a coarse grit and progressing to finer and finer grits to get the wood surface ready for finishing. As an example, you could start with 80 grit and then to 120 grit, and then 220 grit (or some similar progression). There are also a gazillion sources for finish sanding and proper use of sandpaper grits (including a bunch of SE questions and answers).
Once that is completed you can apply the finish of your choice. You can use whatever oil or finish you want at this point. They will not react poorly with the epoxy. There are many questions here regarding applying finishes and polyurethanes.
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I just answered because, as far as I knew, nobody was trying to answer the question and I thought it deserved an answer of some sort. I somehow didn't see VolframK's previous answer at all when I answered, (not sure how that happened) and I didn't want to be seen as essentially reposting his answer.– gnickoDec 3, 2021 at 15:15
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It's perfectly OK to post an Answer that is in essence the same as another one, or shares many of the details. Even if you have all the points of another Answer (rare but not impossible) if you frame the explanation in a different way it could be valuable to the OP or a future reader; also very acceptable if you also include additional info, which you've done here in spades :-) BTW the reason you couldn't see the previous Answer was that it had been deleted by a mod and you don't yet have sufficient rep to see such deletions. Not sure when that kicks in actually, possibly above 1k reputation– GraphusDec 3, 2021 at 18:18
If slab is already flat and prepared the correct order is: fill wth epoxy, sand the fills flat, then apply oil, then apply poly.
Some cracks may go through thickness of wood, to prevent epoxy leaking seal back surface with tape.
Since you will apply poly you do not need to sand above 180.
Wipe all oil not absorbed by the wood.
Wait for the oil to 'dry' one day before applying poly, in case more oil shows on surface of wood.
Rags used to apply oil or poly are a fire hazard, dry flat and then dispose of in trash.
If you will stain then you don't oil. Then the correct order is: fill with epoxy, sand the fills flat, stain, then apply poly after stain is completely dried.
