This lesson is in addition to your sanding chapter. You have information on the various grits, the available types of sandpapers most used in Driftwood sculpture sanding, as well as the types of backing of those sanding papers.
This unit is to be added to that lesson and deals with a more detailed look at sanding surfaces and what to look for and do in circumstances you might encounter.
First let’s explore open and closed coat sandpaper surfaces. Most of our commonly used papers are open coat, best for the woods we work with and provide our best cutting materials. Sandpaper is as much a wood cutting device as a saw, scraper, or plane, just working on a much smaller scale. A closer view of sandpaper will show those cutting grains on the surface.
This is best seen in the coarser grits and can be almost invisible on those finer grit papers. This allows the sandpaper to be used over and over again. It is still wise to clean our papers with an art gum eraser or a block of sandpaper gum cleaner to keep that cutting side at its efficient best. Open coat sandpaper means that only 40 to 70 percent of the surface has grit. These grains allow maximum cutting quality while providing the fine shavings or “swarf” a place to go. Manufacturers of sandpaper use two adhesives to insure a bond for the grit.
Some sandpaper is advertised as non-clogging or stearated. These papers are covered with zinc stearate (a type of soup, actually) which helps the spaces between the grains from clogging with swarf. This type of paper is really only good for working with resinous woods. When sanding pitchy wood the action of sandpaper heats the surface and the resin becomes molten, stearates pick up the hot resinous swarf and make it slide off the slippery surface.
Closed sandpaper is used primarily for metal and glass, but we also use it for finishing, burnishing at lower grits, and enhancing already sanded surfaces. Much of our foam backed paper is closed. But not all!
For the most part, we try not to skip grits in our use of sandpapers. 100, 120 or coarser grits can have their scratches sanded away with 180 grit paper, but not as easily or as quickly as if you first used 150 grit. So go to a well-stocked hardware store and learn the grid ingredients, then fill in the blanks in your equipment. Having the selection of grits will ensure a beautifully finished piece done in the right order.
Of all the jobs involved with creating a finished sculpture, we are all aware that sanding is the least fun job, the most underdone, causing judges to mark your piece as “needs finishing”or “tool marks” and the most difficult to complete. But once you have successfully finished a piece you are aware of the great satisfaction of having created a beautiful work of very unique art!
Just remember: sand, sand, sand!
Arline De Palma