Help/advice for finishing black walnut slab
I picked up a black walnut slab to make an end-mounted cantilever computer desk out of (the middle piece): slab
It's dry, rough sanded and planed, it just needs a little finish sanding and coating.
Anyone have any tips on finishing it? What I'd like it to look like when done is essentially this, color-wise: Ideal result
Is that difficult to achieve? I only have a little experience with stain/brush-on poly. I'd like it to have a reasonably tough, preferably waterproof topcoat. I'm also considering trying to keep the bark on one edge, I know as a first slab project this may be unwise but I really like the cut edge of the bark.
Thanks in advance!
Posted Feb 10, 2015, 9:17 PM UTC
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The "Ideal result" picture looks like someone planed the slab then hosed it down with water. I can still see the milling marks from the planer :)
This is not a difficult look to achieve.
Start by filling in any surface imperfections. Epoxy is a common choice for this. Some people like to mix stuff into the epoxy to darken it. It's best to use epoxy that's made for this purpose (e.g. west systems) because hardware store epoxy will look like crap.
After that, surface prep is of paramount importance. It helps to have good top lighting and side lighting that you can switch on and off. Sand with a grit, wipe with mineral spirits, and check under both top and side lighting to make sure you've eliminated scratches from the previous grit. Only then should you move up. By the time you finish with 220 you shouldn't be able to see scratches at all.
Don't let the sander dig in. Keep it flat and move about 1" per second, like mowing the lawn with the grain. Treat it as a meditation. Don't swing it back and forth and every which way.
After sanding up to ~220, this is what I'd do:
Using General Finishes Arm-r-seal.
The above is the procedure I used on this and this.
I found this video (paid) to be helpful while learning this finishing technique.
Thank you for taking the time to write all that out! Yes, the ideal is just a planed piece sitting out in the rain. I really love the dark colored core with the bright sapwood, so that's what I'm shooting for.
I have a west marine shop near me, so I think I can get the epoxy pretty easily. I'm honestly not all that concerned about an ultra smooth finish so I'm not sure how much I'll be sanding it. I kind of like the rough planed, farmhouse look. I do have a delamination in one spot I'm going to have to resin fill, though. It's not all the way through so I'm not concerned about it, it'll be the bottom of the piece.
Will the arm-r-seal tone the sapwood significantly? The stuff you did looks really good, I'm just hoping to keep the sapwood as light as possible for good contrast.
Arm-r-seal shouldn't tone the sapwood. It will just make it look wet, like the picture.
Using a film finish like Arm-r-seal without sanding is begging for a bad result. Varnishes are meant to level into an even film over a smooth surface. If you apply them to an un-smooth surface, they can't do what they're meant to do.
Your piece looks like it was planed by a machine. While I'm all for getting rustic now and again, I'm not sure of the aesthetic value of preserving planer marks.
For a rustic appearance, consider planing by hand instead of sanding. Because a hand plane cuts instead of abrading, it leaves facets in the surface. They still finish well with varnish, but it has a subtly more rustic and hand-worked appearance. If you use a cambered iron and take a slightly deeper cut than your average smoothing plane, you'll get a more pronounced texture.
You might also consider wire brushing the surface. This is another common technique used to create a rustic look/feel.
In any case, if you're looking for more of a raw wood look, I would use an in-the-wood finish, not a film. Probably an oil-varnish blend. Check out this video for an overview of some of your options.