In this article, we’re going to talk a little about how water affects your wood furniture and we’ll talk a little tiny bit about what you can do about it.
Think of the cells of wood in your desk, table or chest of drawers as a bundle of drinking straws. They started off round but when the wood gets kiln dried the straws flattened out. It’s this shrinkage that explains why none of your 2x4s actually measure 2 inches by 4 inches.
Even with the best of wood finishes and even if Johnny never spilled water on your furniture, it would continually absorb and give off water from the moisture in the air. This absorption makes the cells in the wood swell and shrink, causing wood movement. Unfortunately, the surfaces of the furniture get more exposure, and hence more moisture, than the rest of the furniture so part of it moves more than others.
In fact, the kind of damage that wood gets will tell you a little about how it absorbed the water. If one side of a board gets more moisture than another, you’ll get cupping, the kind you see on your outside deck. The ends of a board are more likely to absorb water and, in this case, the middle of the board serves as a clamp, preventing movement. In time, this causes cracks along the end of the board. If water gets on the surface of a board, for instance from setting a plant on top of it, the dry cells act as a clamp. This causes the cracks that you see along the surface of a flat board.
Even if it isn’t enough to cause wood to crack, this yearly cycle of absorbing water and drying out will make screws and nails loosen, loosen up the handles on drawers, make the joints on a drawer looser, and most disastrously, loosen the rails at the bottom of a dining chair. At least that’s how I’m explaining what happened to Grandma’s chair after I sat in it.
Sadly, there’s not much you can do to change the way Mother Nature works. Wood that is finished on all sides will absorb less water than if some surfaces were left unfinished. But even finished wood absorbs moisture.
If remove you a screw and the hole is too big, you can sometimes fix it with a wooden kitchen match. Put the wood part in the hole and break it off. Then put the screw in again. You’ve effectively made the hole a little smaller.
Cracks and checks in wood can sometimes be fixed with wood putty. There are three types: Nitrocellulose-based, Acrylic-based and Gypsum-based. Nitrocellulose putties dry very quickly but require an acetone based solvent (think finger nail polish remover) to clean up. Acrylic fillers have the advantage that they can be cleaned up with water until they dry but they take longer to do so. Gypsum fillers are usually sold dry and mixed with water before applying. Remember that putty shrinks as it dries too, so when you apply it with a putty knife or the flat of a screw driver blade, leave a slight mound. Don’t manipulate the putty any more than necessary. The binder is made to adhere to wood and a little will stick to anything it touches. Unfortunately, it’s going to be almost impossible to exactly match the finish that you have on the furniture so you’ll have to restain and refinish anything you’ve puttied, at least anything you can see. I’ve used a combination of Elmer’s Glue and sawdust to make my own putty but I have to be careful not to use too much glue or the patch will look too dark.
I apologize that this article is more information than it is help, so next time we’ll talk about how to repair wood finishes. As for what happened to Grandma’s chair…that’s my story and I’m sticking to it.
If you have questions about any of these articles, or suggestions for future columns, you can always drop me a line at firstname.lastname@example.org.