Behind The Scenes: Sanding in Stages October 24 2014
Sanding is critical to the ultimate success of a furniture piece. A good sanding job can be as important to the finished result as the design or the joinery. In the past a variety of implements have been used to smooth wood from sharp stones to sharkskin. These days there is a seemingly endless array of sanding tools, aids and abrasives designed to make our work faster and easier. Even so most woodworkers still dread sanding!
This is a real shame as sanding is most certainly one of the most important aspects of producing a truly fine piece. No matter the time and care that go into the making of the rest of the piece, it's overall beauty is predetermined be how well it has been sanded. No finish is able to cover up a mediocre sanding job. Sanding doesn't have to be so much of a chore however, if you break the job down into it's various stages and integrate the smoothing process with the repair and restoration of a piece of furniture.
Sandpaper - originally screened particles of glass or sand glued to paper backing, today true sandpaper is near impossible to find. It has been replaced by synthetic and natural minerals that are much finer and harder. Abrasives are now available in a huge range of grits well exceeding the 12 to 600 that existed 20 years ago.
Non-paper abrasives - In addition to sandpaper nylon pads and steel wool are available. The pads are very flexible and last much longer than steel wool. They come in different grades from coarse to fine and are good for wet sanding because they're unaffected by water, oil or solvents. Steel wool is good for finish work and the coarser grades work well for stripping wood and for routine chores like metal cleaning. Steel wool is best for finish work as it cuts better than abrasive pads. It also burnishes the wood slightly giving it a better sheen.
Sanding as you go produces much better results and takes monotony out of the work. After sanding all major flaws out of a piece joint all the edges and finish with a handplane. Next glue up any wide panels such as tabletops. While they're drying, sand the rest of the flat parts with a belt sander using 120 grit. All parts that can't be sanded by machine hand sand at the same grit. Brush each piece thoroughly before and after sanding to remove residual grit - it is often the cause of mysterious scratches that appear later on. Check over your work and apply drops of water to any dings to raise up the fibers. By this time wide panel glue-ups are dry enough to remove clamps. Now is a good time to use an old blade to remove excess glue before it dries up completely - if you don't do this now it can lock moisture into joints causing problems later on.
Next use a half sheet orbital sander with 150 grit aluminum oxide paper to go over all the surfaces again. A good orbital sander does an excellent job removing wood quickly while maintaining flatness. Always use the largest sander that will do the job for ease of sanding and speed. Move the machine back and forth slowly with the grain applying only enough pressure to maintain control. By applying slightly more pressure on the back of the sander on the front stroke and slightly more on the front of the sander on the back stroke you have more control and the machine should perform better. Moving slowly minimizes swirl marks by allowing the sander to erase them.
When finishing often oil is an excellent choice as it allows the texture of the wood to come through, sanding only to a 150 grit finish is preferable with oil as it is a penetrating finish and the finer you sand the less penetration occurs. To allow for this apply your first coat of oil before you go to a finer grit.
For items requiring more protection use a surface such as varnish or lacquer. Continue sanding to a 220 grit for a varnish finish and 320 for a lacquer finish.
by Gary Straub
From Fine Woodworking issue #99