I have a big disk of wood, a cross section of a tree. This was saved from a tree cut down “about four years ago” and I just bought it from a sort of an antique and nice junk dealer for $5. It is one hundred thirty two inches in circumference and about five inches thick. I thought it might make a nice display piece if I finish it to make the rings easily visible, and mark them by year – with some luck it may predate the American Revolution. The rings are hard to count right now, fairly indistinct, and I’m looking at a sawn face. The bark is still on it and it is very deeply fissured; looking at trees in the area of similar size with similar bark I might guess it is white oak or possibly chestnut oak (fairly rare but common in this one area). There is a lot of dry hardened sap around the epithelium on one face, and also a lot of what looks like synthetic pillow stuffing and the odor of sheep (no idea what these obscure clues mean if anything).
How do I finish it to make the rings clearly visible?
I am guessing this process will start with a lot of belt sanding using the coarsest belt I can find, something in the 30 to 60 grit range. I’d like it to be flatter at least on the smaller scales, and there is certainly a lot of fuzzy sawn wood to remove to get down to more clear grain.
How might I varnish or protect it to make the rings nicely visible? I think I do NOT want to stain it, as the more porous lighter wood would absorb more stain making it darker, whereas the denser darker rings would absorb less stain, so I’d lose contrast.
It might be that I can test finish areas on the uglier side to compare a few options.
The diameter works out to 42 inches if it were perfectly circular, which it almost certainly isn’t, but if it is in fact an irregular perimeter, then that means that you will be able to take it to a cabinet shop and have them feed it through a wide belt thicknessing sander. These machines can handle up to a meter wide workpiece … there may be wider machines still ( if there are I haven’t seen one) , but a meter wide should suffice with any luck.
You would have to pay the shop for a belt, but in terms of time saved and quality of finish compared to trying to sand it with a hand-held belt sander, it’s a no-brainer.
Once the saw marks have been rough-sanded out by the machine, and the surface leveled, then you could sand it with a hand-held random orbital sander to your heart’s content.
The finish would be best accomplished with a poured epoxy resin, btw.
If you do go the epoxy route, practice on some scrap pieces before you do the trunk. That stuff is finicky. You’ll need a way to tape around the sides to prevent the epoxy from running through any cracks, and you’ll need a heat gun or blowtorch to pop air bubbles in the resin before it cures. Make sure you use a resin specifically formulated for finishing; “Liquid Glass” is one brand.
This is probably a good idea - the process is known. One of my hobbies is antique radios and we hear a lot of “…the idiot used polyurethane” to refinish some antique. Polyurethane is a permanent layer of plastic and if you screw it up you can’t strip it or fix it. I don’t recommend it.
Wood beach and stain MIGHT BE good way to highlight the rings. It works on old radios when one wants to highlight wood grain that was hidden under old dark toner.
I live near a “crafty” area of the country and there are several woodworkers that build natural slab tables. You might get the legs built, the top smoothed and trimmed, then look for help for the final finish.
If it’s been sanded properly the right stain will highlight the grain. I’d suggest getting a cabinet maker to do that. The surface has to be flat and then smoothed with the right grit so only minimal stain is absorbed. Radial splits were already mentioned, I agree you don’t want to wait to get it finished and sealed. You may be able to find wood treatments that will prevent drying, there are some PEG products that are used to keep wood ‘green’.
The easiest way to flatten and smooth large wood slabs is to make a router sled. Here is one vid but there are many more: 006 - How to Construct a Router Sled for milling large boards - YouTube
Once you have made a pass with the router, you can then proceed sanding, starting about 60 grit, then 80, then 120, then 220. If the wood is about 5 inches thick and 5 years cut, then moisture content should have stabilized where checking (cracking) should not be too much of a problem. If there are major checks, you could add a bowtie or two…or three. If there are any holes, they can be filled with two part epoxy prior to sanding.
The next videothat follows shows it used on a slab of a big tree. It looks like he’s going to show what he used to bring out the grain in other videos.
There’s pretty nearly no way to circumvent splitting with a whole slice of tree (well, you can soak it with polyethylene glycol, but that makes finishing tricky).
Better to embrace the splits. I’ve seen some beautiful examples where cracks were filled in using epoxy loaded with pigment or pieces of mineral such as malachite.
That is a very nice table, but not directly comparable to the OP’s piece, which is a transverse slice of a tree, which probably already has cracks in the presentation faces. There’s no way to close up those kind of cracks, so the alternatives are to fill them, or leave them open.
There is a radial crack at least half an inch wide at the edge, and numerous more that are much smaller. I’m fine with that and will embrace them. And I’m not planning a table. The tree’s rings are the only rings I want! I think wall mounting more likely.
The piece is dished something like an inch or so. Contemplating whether to embrace that too.
I’ve built a lot of furniture, and I’ve never seen a case where stain hides the grain. Stain always enhances the grain in my experience, which is also what I’ve read in all woodworking books and magazines I’ve read. Google “wood stain enhance grain” for specific ideas about stains to use. If you’re only going to be showing one side of the slab, you can experiment on the other side to find a stain formula that you like.
But for best effect you’ll definitely want the wood to be as smooth as possible. Your mention of dishing is very important – it makes the idea of using a thickness sander much less feasible. I was originally going to suggest initial flattening with a hand plane followed by a belt or random orbit sander, but this again will not work well with a dished surface. If the surface were nearly flat, I would say start with a hand plane, using the normal flattening technique – first diagonally across the grain, finishing with the grain. Frankly I’d be more inclined to get rid of the dishing, although an inch deep is going to involve a lot of planing. Maybe rent a power planer. Follow the planing with sanding using at least 3 grades of sandpaper, something like 100, 220 and 400. Make sure you THOROUGHLY sand with each grade before moving to the next. It’s a very common mistake to end up finding big scratches from the earlier grades when you’re done with the fine grade. The smoother the finish, the better it’s going to look when it’s stained and sealed. Be prepared for a lot of work. I recently finished a cabinet top that was 22" x 64", about the same area as your slab, and it probably took about 8 hours of planing and sanding to finish. If you’re going to flatten the dishing, it will be a lot longer.
Do you know where the slab has been situated for the last 4 years since it was cut? The normal rule of thumb is wood should be air-dried for one year per inch of thickness. So your 5 inc slab should be dried for 5 years before working. But that assumes it’s been sitting in a good drying position, exposed to air on all sides. If it’s been sitting on the ground or a floor, it may need more time. If it’s been covered on both sides, you’ll basically need to start the 5 year clock right now. Using wood that’s not completely dry means the wood may continue to shrink or move – this is a much bigger issue for furniture than for a display slab, so perhaps you can skimp on drying time, but I don’t have experience related to what happens to insufficiently dried wood after it’s sealed.
A plane? This is a cross section of a tree. The entire exposed surface is end grain. Can I plane that? Is planing a good method for end grain? Do I have to do something special to plane that? My limited experience with planing more involves the edges of old doors…
Also, about the stain and the grain, I used to build big bookshelves out of white pine, like 1X10 planks. I would stain only. We are talking very utilitarian bookshelves, and I don’t count this as “furniture building”. Nevertheless, I did notice that dark stain would penetrate the softer whitish areas more and the darker brown areas less, and create a “negative”. Not so? Especially, with end grain, I would expect penetration to be pretty extreme.
More careful examination makes me think maybe this is pine. I think by smelling the bark on the cut face I get a hint of pine smell. And the rings are actually fairly coarse. I can count them more or less well along a radius starting at the center, which gives me 26 rings in 6 inches. And along a radius starting at the periphery, giving about 33 in 6 inches. So at a rate of about 30 rings per 6 inches, or 5 rings per inch, that indicates a tree around merely 100 years old. Also, having only 5 rings per inch seems pretty fast growing, like a pine and not an oak – but I don’t know much about wood so I’m guessing here.
I checked the dishing more carefully and on the neater face, which is convex, the center is outboard of the periphery by very close to one inch. The opposite face is concave but it is also not so regular. The chainsaw appears to have cut less neatly and there’s a sort of a radial mountain range that deviates from gentle concavity by about half an inch. I think it is hard to get concave or convex sawn faces more than 40 inches in diameter, I’m going to guess this concave/convex shape arose during drying rather than the original cutting. Perhaps it is a sign the wood spent the last few years laying on a surface rather than exposed to air on both sides.
I don’t know anything directly about the drying or storage conditions until yesterday.
The big radial crack is 5/8" at the periphery and it comes to within about 3" of the center ring. There are many dozens of other radial cracks that are only an inch or two or three long, none of them bigger than a sixteenth at their widest. Again, I’m happy embracing them. I’m actually more worried about filling them with sawdust and not being able to clean them than I am about anything else with them.
Yes you can plane end grain. To be honest I haven’t done it much, but from what I’ve read, the most important thing is to have a very sharp iron in your plane. You may need to resharpen it a few times while you’re working.
Yes, stain penetrates end grain more. When building furniture this is a frequent problem. I have a coffee table I built long ago where the edges are darker than the top because the stain penetrated more there. But in your case it’s all end grain, so that’s not an issue. And yes, the light grain will darken more than the dark grain, but normally the stain as a whole is darker than any part of the wood (especially true if it’s pine), so the overall effect is to enhance the grain. But again, I would definitely experiment on the back side. Be sure to smooth the area you’re experimenting on to match how the front will look; stain acts very different on smoothed wood vs. rough.
If sawdust gets in the cracks, you should be able to just vacuum or blow it out, as long as it’s dry (that is, do this before you apply any finish).