Furniture's Killing Season
It’s winter in Northern Ohio, and with the cold weather comes the real test of my woodworking skills. I’m not worried that my finishes will chip or that my joints will fail; I’m worried about how the dry air might twist and wrench my work all out of shape.
In one way, building furniture used to be easier: houses were heated little or not at all. Even homes with multiple fireplaces were still chilly and the air relatively moist. With the advent of central heating (especially forced-air heat), the winter environment in homes changed dramatically. Modern furnaces can wring every drop of water out of the air, heat it up, and send it blasting fourth, parched and thirsty. As this air flows over solid wood furniture, water comes pouring out. As water leaves, wood shrinks, and the flat-sawn boards that most of us use are especially vulnerable to wood movement from falling humidity.
Many antiques have fallen victim to the sudden invention of forced-air heating. Chairs are probably the most vulnerable and as old joints shrink, rungs come popping out of posts while astonished sitters find themselves suddenly on the floor. I bet many of these chairs have been thrown out in disgust.
As builders, we have to think about the brutal dryness of winter, but we have many tools to keep our work together. Kiln-dried woods start out much drier than air-dried stock, and they might be more resistant to winter’s arid touch. Unfortunately, many of us build in the summer, when garages and sheds are tolerably warm. Our un-airconditioned workspaces are often humid in July, and that hyper-dry wood will pick up a lot of moisture during the build. As we put pieces together, we must always think about what will happen when the wood shrinks.
Nothing can stop wood from trading water with the air around it, but film finishes greatly slow the transfer of water in and out of a piece. Shellac, lacquer, polyurethane, and Danish oil will all ease the transition from wet summer to dry winter and give your furniture more time to settle into the winter climate. Oils are a bit less protective and the modern “hard waxes” haven’t been around long enough to see decades of changing seasons. Only time will tell how much they shield our furniture from the dryness.
Finally, think about where your pieces will sit, whether in a client’s home or your own. Years ago, I built a small bench in the Mission style. My family and I use it for changing shoes and boots, so it has to be right next to the door. Unfortunately, there’s also a heating register in that same patch of floor, so my little bench is reliably blasted with desert air straight from the furnace. I can see the wood move each season and watch as tiny gaps open up in the notched joinery, but I built the piece using cut nails driven into pilot holes. As the boards shrink and swell, the nails bend and flex, and after three winters in this harsh location, the bench is holding strong.
As you look around your house, maybe you want to juggle a few pieces around. Move this one away from the heating duct and shift that one to a different room. And this summer, when you set your hand to the year’s new furniture, think ahead to the dry days and wild swings that lie waiting for each piece you build.
Winter is always coming.