Sandpaper is probably one of the most important tools you can have in your workshop. It can be used to refinish furniture, brighten old brass, smooth your project made of wood, remove rust, and more. We typed sandpaper into the search engine of our website and got 85 matches. That’s a lot of projects.
In 1965 “Days of our Lives” premiered on TV “Like sand through an hourglass so are the days of our lives”. Today you will learn all about sand only in this case it is the kind that is stuck to paper. Right again, we’re talking about sandpaper, technically known as a “coated abrasive”. Today, we are going to learn about those confusing but important numbers printed on the back, which provide a wealth of information if you can break the code. This will involve learning about the term “grit”. So, tighten your seat belt, hold on to your seats and here goes.
Believe it or not, sandpaper dates back to early Chinese craftsmen who, nearly 800 years ago, used natural gum to bond crushed seashells to parchment paper. Amazing isn’t it? However, as you may have guessed there’s a little more to sandpaper these days.
When it comes to sandpaper, seashells aren’t so popular any more. Today, four types of abrasives are used and each is available in various particle sizes or “grits”. Remember the term grit. 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 really cool. It’s kind of self-sharpening. As you use it small particles of the grit break off revealing new sharp edges – self-sharpening. 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 actually 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, it can be used for finer work. Keep in mind that 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. Not to change the subject, but 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.” Last but not least, there’s ceramic abrasive. It isn’t as sharp as the others, but it doesn’t have to be. That’s because it is generally used for machine papers such as those used in disk, belt and drum sanders.
As promised we told you that we would explain what the secret numbering code on the back of the sheet meant. Actually it is quite simple. If it says 80 it means that the abrasive particles passed through a screen with 80 openings per inch. If it says 200 then it means that the abrasive particles passed through a screen with 200 openings per inch. Get it? The lower the number the more course the grit and the more surface will be removed with each pass. By the way, sanding is a multi-step process. There isn’t any one grit size for all jobs. In fact, 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 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 actually polishes the wood. For oiled or varnished finishes 220 grit is a must. One company we know of that makes a wood finishing oil called Penofin 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. It is magnificent.
Did you know that sandpaper can be used for metal polishing as well? You can revive badly pitted brass in no time. Even though the brass may be tarnished and pitted a thin protective coating (usually clear lacquer) must first 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 may exist. Yes, as with wood, the sandpaper will scratch the surface, but additional finer sanding steps will gradually 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 400- to 600-grit. Then the brass polish.