Sandpaper probably is one of the most important tools you can have in your workshop. It can be used to refinish furniture, brighten old brass, smooth your wood project, remove rust...and more. We typed sandpaper into the search engine of our Web site and got 85 matches. That's a lot of projects.
Sandpaper technically is known as a "coated abrasive." Those confusing, but important numbers printed on the back of sandpaper provide a wealth of information, if you can break the code. This will involve learning about the term "grit."
Sandpaper dates back to early Chinese craftsmen who, nearly 800 years ago, used natural gum to bond crushed seashells to parchment paper. There's a little more to sandpaper these days.
Today, four types of abrasives are used and each is available in various particle sizes or "grits." The abrasives are aluminum oxide, silicon carbide, red garnet (or garnet) and ceramic grit.
- Aluminum oxide papers are most common and are excellent when used on wood. Aluminum oxide is kind of self-sharpening. As you use it, small particles of the grit break off revealing new sharp edges. Talk about lasting quality.
- Silicon carbide also is sharp, but doesn't crack and break like aluminum oxide. This makes silicone carbide more appropriate for harder surfaces such as plastic and metal.
- Garnet is the old, economical standby. Unlike aluminum and silicone, garnet gets dull as it is used. This can be an advantage, as it can be used for a rough sanding first and then, as it wears down, for finer work. Sanding a surface until it shines is what ordinarily offers the finest- looking finish regardless of the wood or type of finish coating. Of course, it takes practice to get a feel for how quickly the paper changes condition, but many experts swear by it.
We know one hardwood floor refinisher who only uses USED 220-grit sanding mesh for finish coating because, as she puts it,"the more it gets used, the smoother it cuts."
- Finally, there's ceramic abrasive. It isn't as sharp as the others, but it doesn't have to be. That's because it generally is used for machine papers such as those used in disk, belt and drum sanders.
As to the secret numbering code on the back of the sheet: It is simple. If it says 80, it means that the abrasive particles passed through a screen with 80 openings per inch. If 200, the abrasive particles passed through a screen with 200 openings per inch. The lower the number the more course the grit and the more surface will be removed with each pass.
Sanding is a multi step process. There isn't any one grit size for all jobs. We recommend at least four grits for most jobs. First, we like to do a course sanding using 30- to 50-grit paper to remove deep gouges and imperfections. Next, 60- to 80-grit paper begins to remove the deep scratches caused by the first sanding. This is followed by 120- to 150-grit and finally by 220-grit. Sanding with the finest grit polishes the wood. For oiled or varnished finishes, 220-grit paper is necessary.
One company that makes a wood-finishing oil recommends the use of 220-grit sandpaper between each coat of oil to help force the oil into the wood and to increase the luster of the finished surface.
We've tried it. The results are magnificent.
Sandpaper can be used for metal polishing as well. You can revive badly pitted brass in no time. Even though the brass might be tarnished and pitted, a thin protective coating (usually clear lacquer) first must be completely removed before sanding. Use paint remover to do this. Omitting this step will make the sanding considerably more difficult. Once the clear coating is removed, sandpaper is used to remove the oxidized surface layer of the brass, including any pitting that might exist.
As with wood, the sandpaper will scratch the surface, but additional finer sanding steps gradually will begin to bring you to a point where all you will need is brass polish to render a highly polished luster. With brass the last sanding step should be with 400- to 600-grit paper. Then the brass polish.