Finishing Plan for end-grain Walnut Table

[Spencer Blackman]

Hi all,

I'm a novice working on my first project -- a circular "cookie" cut black walnut slab that I plan to mount on a metal base for a small table. The slab I have is about 25" in diameter (incl. bark) and probably 1 3/4" thick. Since it came to me rough, I had it planed, then did my own (rather poor) filling of the small checks (none more that 1/4" thick) with an artist’s epoxy that dried close to clear, but did absorb into the wood a bit and darken the areas around the cracks. This is especially noticeable in the sapwood. I’ve accepted these discolorations and have sanded down to 150 in preparation for finishing. I’m looking for a relatively dark finish (hoping to obscure some of the discoloration), with a hard, durable, clear coat over top to withstand regular use. While I don’t expect this first project to be my last, I’m in an apartment and don’t have a dedicated work area or a particularly deep toolbox. Buying and using smaller quantities of materials is generally the preferred route for me. Based on reading here and elsewhere (including Flexner), below is my general plan. I’m hoping some of the experts here can help me revise my plan in light of my goals and (low) level of experience.

1. Because this is entirely end grain, I’m concerned with the absorption of any finish. I plan to sand to at least 400 before applying anything.
2. To help prevent absorption, it seems that I might want to apply a washcoat of shellac, maybe in a 1# cut, sanding afterwards with a 320-grit sanding sponge.
3. Next, I planned on using Formby’s Tung Oil finish. I realize that this is a varnish and may not even contain tung oil. My goal with it is simply to darken and add a bit of shine, so I was thinking about 2 coats, using the same sanding sponge in between and after.
4. To seal and add a bit more shine, I plan to use at least 2 coats of Minwax wipe-on poly.

I would love to hear if this sounds like a reasonable plan, and if not, what steps I should reconsider. As a complete rookie, all feedback is good feedback! Thanks in advance.
Spencer

[Steve Schoene]

You are going to have absorption, but it's not something you should try to avoid. Unless you get considerable finish absorbed into the end grain--ON BOTH SIDES you are going to have more than a few checks appear. Shellac would be good, but I'd expect needing several coats of 2lb. cut. Keep applying additional coats of shellac until the wood stops absorbing. The reason for shellac is that it is the best finish for slowing the transfer of water vapor, and it is changes in moisture that will cause the disk to split. Once the wood stops absorbing shellac--is just beginning to show a shellac film on the surfaces, then you can shift to the varnish. The Formby's is a relatively low solids wiping. varnish and ought to work just fine over the shellac. If there is a chance that you would end up with some other varnish, such as a polyurethane varnish, then the shellac should be dewaxed, such as Seal Coat from Zinnsser, or dewaxed shellac you mix from flakes.

[Spencer Blackman]

Steve, thanks for the reply. That was one my my main concerns, than the shellac washcoat would prevent the varnish from doing its job. Good to hear that it won't. From what I've read, de-waxed is definitely the way to go, and SealCoat seems like an easier option since it'll be readily available. The majority of my effort to fill cracks and checks has been on the top of the cookie, so there are still some pretty wide chasms on the bottom. Would you recommend sealing these up prior to shellacking or just leave as is? I'm a little worried about bleed-through -- what kinds of dryimg times do you think I can expect with Sealcoat or shellac from flake?

Thanks.

[Steve Schoene]

Shellac dry time will be under a half hour for the first couple of coats though with more coats the time to dry would be extended a little. You don't want to build really thick shellac films in any event.

I would treat the bottom substantially the same as the top to ensure than moisture transfer rates are similar to reduce the risk of warping.

[Spencer Blackman]

Steve,

Thanks for the tips -- i wouldn't have thought to seal off the bottom. All finished now and it looks great.

S

[Scott Holmes]

Why put Minwax poly varnish on top of Formby's varnish?

[Andy Pratt]

Not trying to turn the thread into something you didn't ask, but most people would be very nervous about making this type of table without stabilizing the wood beforehand with PEG. This is going to crack severely on you (a big, ugly, gaping crack, probably an inch or more wide and full radius length), with probably 95% certainty, if you don't. A cookie cut of a log that large really is guaranteed to have at least one major crack in it once it is fully dry. If the wood hasn't been kiln dried or air dried 1-2 years before you start you are in for almost certain disappointment in regard to cracking.

I say all this because you said you are just starting out and I don't want you to put too much time into something that won't work out. If you are committed to the project, look up PEG and use it for this, then figure out what finish to use as a side point after you are sure it isn't going to crack on you. Or, if the crack is not bothersome to you, let it crack before starting your finishing.

4-6" seems like the diameter limit for where you can expect to have a cookie cut that doesn't crack through the radius, so you really are well beyond the limits of that with a 25" piece. You have a neat piece of wood there though, so do it right and you'll have a beautiful thing.