Tips on sanding a bowl
In order to get a really smooth finish on wood, there are a few processes I undertake to help me get the best result. My more intricate, natural edge bowls are harder to sand, so a lot of patients is essential! Generally speaking, it’s much easier to get a quality finish on smaller items, since they can be spun very quickly on the lathe and have less of a surface area, which requires attention.
When a bowl has been turned, there will usually be areas of torn grain, ridges and other defects, which require sanding. Making sure the tools are sharp will reduce this, but not eliminate it. If kiln dried timber is being used, this will give a better finish in the end, but it’s harder to work with and often leaves splintered grain and areas of roughness.
I start the sanding process with a drill mounted sander. My rather worn example is illustrated in the photo below! It consists of a conical shaped piece of foam with Velcro backing and is mounted to a steel shaft. This accepts three inch diameter Velcro backed sanding discs and its flexible construction is designed to follow the contours of the timber. I usually start with a 120 grit sanding disc, but do use a coarser 60 grit disc on occasions. A good example of this would be the initial sanding of the base on a very deep natural edge bowl, where access with a turning tool has been restricted.
I use a combination of power sanding and hand sanding to achieve the best result. Sometimes, the drill can remove softer grain without noticing and this can leave a dip. Because of this, I always use a small block of wood and sandpaper to flatten any irregularities. Certain timbers, such as ash for example, have a very fibrous grain and this can feel rippled, even when completely smooth. A sanding block flattens the grain and improves the overall effect.
I always like the inside profile of a bowl to follow a perfect arc, which extends from the rim to the base. This can be hard to achieve, but does add that ‘wow’ factor when someone picks it up. The odd bump or ridge can be removed when the bowl is stationary, but will then need a quick sand over whilst the lathe is spinning, in order to remove irregular sanding marks. The most important thing is to make sure all sanding lines have vanished before moving to a finer grade of sandpaper - Just one coarse sanding mark will stand out like a crack when the oil has been applied!
When I’m happy with the shape, I coat the whole piece with a shellac sealer solution (half shellac and half thinners) and leave for about 20 minutes to dry. The shellac soaks in, hardens and provides a better surface for the finer grits of sandpaper. I will then run the lathe in reverse and sand with 240 and 400 grit discs. Reverse turning reduces the chance of sanding marks being visible on the final piece. On completing the sanding, I will vacuum the bowl and make sure all dust and debris are removed from the surface. This is particularly important for burr and rustic pieces, where natural cracks can capture a lot of dust.
The piece is now ready to be oiled..
