Softwoods and close-grained hardwoods, such as maple and poplar, are ready to finish after staining. Open-grained hardwoods may require further treatment. Even after the surface is stained or sealed, open-grained wood still has open pores, and a finish applied over open pores may look uneven. To give it a smooth and evenly finished surface open-grained wood is usually treated with a filler after staining. In this article, we'll discuss the best ways to apply filler to your wooden furniture.
Whether you should fill the wood depends on both the wood itself and the finish you want. What is the piece of furniture made of? Bass, hemlock, maple, pine, poplar, redwood, willow, cedar, cypress, and ebony should never be filled; they can be finished immediately after staining and sealing. Ash, beech, mahogany, oak, rosewood, walnut, teak, satinwood, butternut, chestnut, elm, hickory, and lauan are open-grained; they are usually filled. Most of the other hardwoods -- such as cherry, birch, and sycamore -- are close-grained and should not be filled.
Filling is also a matter of personal taste. Do you want a mirror-smooth finish on a formal table, or are you aiming for a more natural-looking finish on an informal piece? Filler produces a very smooth, glassy surface; if you want a more natural look, you may want to leave the pores open. This also affects the finish you plan to use. Under most finishes, open-grained woods should be filled, but if you don't want the piece of furniture to have a very smooth surface, you can finish it with a penetrating sealer, which makes filling unnecessary.
One drawback of filling is that most finishes don't bond as well to filled surfaces. In general, it's best to use a filler only when necessary, such as when a varnish, shellac, or lacquer finish will be applied over one of the open-grained woods listed above. If you're not sure the wood should be filled, don't fill it.
Choosing a Filler
Fillers are available in two forms, liquid and paste. The liquid type is not very useful; it's too thin to be effective on open-grained woods. Tinted liquid filler is sometimes used like lightening stain, to change the color of the wood. In most cases, filling should be done with paste filler, thinned as necessary to penetrate the pores of the wood. If you plan to finish the piece of furniture with lacquer, use a lacquer-base filler or let the filler dry for at least 48 hours before sealing and finishing. If you plan to use a polyurethane finish, make sure that filling is recommended and that the filler is compatible.
There are two types of paste filler. The most commonly available filler is based on cornstarch; it's available in a neutral tone and in several colors. This type of filler should be matched to the color of the wood; it dries only slightly lighter than its apparent color.
If you can't find a color to match the wood, use oil stain to mix a filler slightly darker than the wood; check the labels to make sure you can mix it. More than one application may be required with this type of filler.
The second type of paste filler is called sanding filler; it dries transparent and does not have to be matched to the wood. Sanding filler is silicate-base and requires only one application. Because it doesn't have to be color-matched, it is easier to use than cornstarch-base filler.
Once you have decided on the type of filler, you are now ready to begin your furniture restoration project. Learn the best ways to apply the filler in the next section.