If you are carving basswood or tupelo, the largest pieces you can get are ususally 4×4 or 4×6 in various lengths (although some companies will custom cut it for you). So you will have to glue pieces together for anything larger. Large panels for relief carvings also are usually glued up, but they present some different issues, that we can discuss.
If a piece will be carved on all four sides, or all around (an “in-the-round” carving), then it is usually not as affected by direction of growth rings. Let’s just use the term “bark side” for the area of the wood that would have been closest to the bark. If you look at the end of a piece of wood, you will see a shallow arc or C shape. The convex side is the bark side and the concave side is closer to the heartwood. So, for an “in-the-round” carving, you want the grain of the wood all going the same way, to make carving easier. And it is not really critical whether the pieces are glued up bark to bark, or bark to heart, or heart to heart. Because it will be carved on all sides, the wood cells will be affected equally, and cupping is usually not an issue (like it is with panels). There are more cells on the bark side. Cells can expand because of moisture, or because of cells being removed on the opposite side, no cells to push back against the other side. So that is why bark side usually will bow up….. everything else being equal, there are more cells on that side. But carving away the wood seems to even out the stresses and presasures, and keeps in-the-round carvings from bowing and cupping. Luckily for me, as I have did large pieces with no knowledge of cells and warping! I carved a carousel style rocking horse from 1” boards laminated together, with no concern for growth rings or much else. The laminations allowed me to make mortise and tenon joints that were beyond my skills and tools and the whole thing has not been affected by the past 20 years in the extremes of an attic in the humidity of Arkansas. The inside was hollowed to reduce weight and it was finished with polyurethane. Here are some other examples of “in-the-round” pieces that are glued up.
This guy (William) uses 3/4” pine and scrollsaws general shapes out before gluing them together and carving them.
The artist Gerhard Demetz deliberately leaves gaps and spaces in his glue-ups for carvings that create a dramatic effect. You can see his sculpture glued up, with edges to the front and back, it appears.
I saw a woodcarving at the Crystal Bridges Museum a couple of weeks ago that was carved in 1876 from five boards laminated together. It was often mistaken for bronze, due to the finish applied, but the laminations are apparent, if you know what you are looking for!
Glue-ups for panels for relief carving do pose certain issues and are affected by cupping, unless measures are taken. A jointer is recommended to get the tightest joints possible. While you can use any size board you desire, results will generally be better with 4” or narrower strips.
Gluing with the bark side up as shown in the first example, will cup as shown in the second picture. But there are several ways to minimize the cupping or use it to your advantage. You could turn the pieces on edge and glue them up that way, but it might require a lot of strips to constuct your panel. If you glue them as shown, some pressures will be equalized, simply by carving on the bark side. You would be rqualizing the number of cells. If your carving is quite deep, it may even be necessary to cut some off the back side or cut slots in the back, in order to equalize the stresses there. That has been a common practice for centuries, to balance the stresses created by removing wood from the front.
You can also attach cleats across the back or the sides, dpending on how the boards are oriented, but keeping the grain direction the same on all the pieces will make carving easier. I’m thinking that alternating the growth rings as shown in the second set of drawings, might cause more issues than it cures. Any real life experiences with that? Some carvers suggest that tipping the blade or the fence on the jointer slightly off 90 degrees allows you to introduce a slight camber to the panel, that will offset the pressures released by a high relief carving. But carvers with more experience than I, suggest that simply making several relief cuts on the back of a board will take the “fight” out of it!. No need to fuss with building in camber or worrying about angles.
Just get a decent edge and apply wood glue. Clamp it about every foot, alternating sides, and don’t tighten it so much that it bows! Or get some of those fancy clamps made for gluing panels! Use wax paper or wood strips so the clamps don ‘t leave marks on the wood (react with the glue). Scrape or wipe off excess glue as you prefer.
I use Titebond glue generally, but other glues are useful for certain aspects of carving. I use two part epoxy glue for attaching handles to canes, which is generally endgrain-endgrain with a metal rod. I use CA glue (super glue) in several forms. I use a thicker version for gluing in pins or small pieces of work, like frets on a tiny guitar, or a piece of wood that chipped off (because I didn’t pay attention to grain direction) while carving. The thinner CA glue absorbs really well and is useful for making a delicate piece stronger. I have used on the ears of a horse and on leaves and flower petals. It soaks in and dries quickly, making a delicate piece of wood almost like plastic. Be aware that paints may not adhere very well, especially waterbased. I hope this is helpful and answers some questions. More to come in my next one!
-- Mike P., Arkansas, http://mikepounders.weebly.com