Boiled, my exploration of bending wood with water.

Part 1.

Several years back I came across an article about bending wood to create a traditional Scandinavian box called a tiner, pronounced like the name tina. I was fascinated and began looking into the idea and trying it for myself. Over the next few years I found more information and experimented with different materials and techniques. In 2018, then again in 2019, I entered my research and attempts at recreating these historical boxs in local competitions. The attached file is the documentation I used for those entries, the following is an overview of that information.

Bending wood is fascinating, frustrating, and at times infuriating. In many other aspects of woodworking grain is important but can be worked around, used to enhance, and in essence is part of the beauty of the finished piece. Not so in bending. In bending the twisted grain, the knots, the unusual patterns found within a piece of lumber are often the enemy. The straight, even, uniform, lets face it, boring, grain is pretty essential to getting the bend right.

This entry is aimed at bending for thin walled construction, specifically tine, or svepask, or shaker boxes. For my purposes a thickness of about 2 to 3mm, 5/64″ to 1/8″ is ideal. I usually work with a height of between 4″ to 7 1/2″ and 28″ to 38″ for the boxes I make. My method is to select a piece of lumber that is as straight and flat as I can get it, with a tight, even grain and no knots or holes. As you gain experience you can work some figure into your work but in the beginning, keep it simple.

For lumber I started with walnut, and had a tough go of it. I later moved to white oak and had better luck, how much of that is material selection and how much is further skill development is hard to say. Stiffer and harder woods will be harder to bend and not have much flex in them when you get them to form. Purpleheart, redheart, and paduak are all beautiful but more expensive and harder to get to bend. Pine bends surprisingly well, as does poplar but by far my favorite to bend is ash, preferably air dried ash if you can find it. If you have access to air dried lumber try it, kiln dried lumber does not reabsorb moisture well and the kiln heating makes the wood more brittle, making it harder to bend.

Once I have my board I take it to my table saw. I have a tall sacrificial fence on my saw that I use to keep the board perpendicular to the table and a zero clearance insert. I set my saw for 1/8″ thick cuts and begin by taking shallow cuts from each side until I have a piece free. Repeat until I have gotten as many blanks as the board allows. For some of my bigger projects I can only cut part way and then have to put the board in a vice and finish by hand. Once I have my lathes free I take them to the drum sander and get them smooth and uniform thickness.

If you have a band saw and are more comfortable with using that for resawing thin lathes it will work as well, I found I was more comfortable with the table saw and once I flattened the board I took out as much waste with the sander and the thinner kerf on a band saw, as I did on the thicker kerf on the table saw. Your mileage may vary. A third option is to saw by hand and plane smooth. It does produce a truly distinctive finish that sanding will not match but it is very slow. Again, go with what is most comfortable, and safe, for you in your own shop. Should you be in areas where woodworking is perhaps more prevalent than where I am, you can also look into purchasing presawn pieces intended for inlay or marquetry.

When you have your lathes ready you need to determine how you are going to bend them. Ultimately you are looking at combining heat and moisture to coax the wood to assume the shape you desire. I have experimented with three methods. Direct heat, steam, and immersion. Of the three I prefer immersion.

In all cases you need to submerge the wood to allow it to soak up as much water as possible. Water will both soften the wood as well as helping to transmit heat more efficiently without burning.

Direct heat involves soaking the wood and then exposing it to directed heat, such as heating a metal pipe, and pressing the wet lathe to it to transfer heat and using the pipe to impose a uniform curve. You need t ensure you keep the wood wet and continue to reapply water without dissipating the heat to much as you do so. I find this method very fiddly and imprecise for what I am trying to do.

Steam bending is a pretty well known process due to the rise in you tube videos on steam bending boat planks and the like. You build a cabinet and place your wood inside, connect a source of steam and then let the steam go to work on the wood. Again, pre soaked wood preforms better for me even steaming. One thing of note, do not make your steam box to tight, you need to allow for pressure to escape but try to keep as much of the heat and moisture in. To much pressure could cause your steam box to fail explosively. I successfully bent with a steam box but found if clunky and I got scalded a few times, additionally the wod can get cooked and become brittle.

My favorite method currently is hot water immersion. it also has the benefit that it is possible to do it at home without needing large space for hot metal or a bulky steam box. I use a hot water tank that I have cut in half lengthwise over a 3 burner propane camp stove. I soak my lathes over night and then heat the water to a temperature that is uncomfortable warm to put your hands in but not so hot you burn yourself on contact. If the wood seems to be softening but not enough I can give it more time or tun up the heat without having to rebuild the pressure and heat from a steam set up and the wood doesn’t face becoming brittle.

To form my boxes I have created forms out of plywood in a number of sizes. I have put holes into the top and bottom of the forms about 1/2″ from the edge that are big enough for my spring clamps. When the wood is sufficiently supple to bend I place it on the form, place a cull over it for uniform pressure, and then clamp both sides with spring clamps. I work my way around as quickly as I can to retain hear and try for an even smooth bend using the culls and spring clamps.

Once the lathe is bent completely around the form and clamped in place set it aside to dry overnight or until the outside is dry to the touch, whichever is longer. From that point carefully mark where the ends over lap and remove the lathe from the form. At this point the lathe will still have considerable spring back due to the moisture trapped between the lathe and the form. Carefully re-bend the lathe back to the marked overlap spots and re-clamp with calls on either side but off the form.

Let the lathe dry at least 24 hours. Once the lathe stays in shape after removing the clamps it will be ready to glue. Carefully apply glue to the overlap and reclamp to let dry. Be sure that the pieces are clamped and glued straight and square so the walls are vertical and it will sit flat on the bench. Once dried remove the clamps and check to make sure the top and bottom are flat and parallel, and that there is no glue squeeze out to remove. Sand the body inside and out.

At this point you will want to make some decisions on proportions and aesthetics. For my boxes I use 5/8″ thickness for the top, the base, the handle, and the snaps or locks depending on what type of box I am making. You may prefer a thicker or thinner handle or a thinner top, it’s all on your personal preference.

Once the body is glued and the top and bottom are flat I lay the body on top of the material I want for the base and trace both the inside and outside contour of the box. You can try cutting the base off of the pattern block but I find that each box reacts a bit different so I trace directly for each box to get the best fit. Useing the band saw I then cut the base out close to the outside line of the box, followed by going to the bench grinder to bring it right to the line. I will then cut a rabbet into the base about 1/4″ down so that the box body fits snugly.

Once the base is fit snugly I will use a small amount of glue and dowel the base to the sides by going through at an angle. These are pretty small dowels, about 5/64″ dia to 1/8″ depending on the side of the box. For dowels that small round toothpicks work well, as do skewers for cooking. I use a bit of glue with the dowels just to be safe but with a proper fit you don’t really need it. Trim off the excess and sand flush.

Part two will discuss different lids and how to fit them.


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