Sanding is one of those tasks that nobody enjoys. So in order to get the best results with the least amount of effort, we need to consider the things that have the most dramatic effect on our sanding efficiency.
If you understand sandpaper lingo, you’ll find it much easier to choose the right material for your work. That means you’ll get the job done faster, you won’t waste as much paper, and the results will be better. First let’s talk about the grit types:
Aluminum Oxide: This is the most common material used for woodworking. Its very durable and lasts a long time because it is friable. That means as you use it, the grit breaks apart and leaves more sharp edges. So the paper sands consistently and lasts longer. You can use this stuff on more than just wood and you’ll see it used for sanding finishes, plastics, metal and paint.
Garnet: Garnet is a natural abrasive and it is generally only used to sand wood. The reason is because it is NOT friable. Instead, the grit wears down as you use it and ultimately leaves the wood with a smoother surface than aluminum oxide sandpaper. But I get such good results with my standard aluminum oxide papers, I don’t really bother much with garnet.
Ceramic: I don’t even have any of this stuff in the shop. Its very hard and durable and generally used for aggressive stock or paint removal. Common to see these in more aggressive tools like belt sanders.
Silicon Carbide: Easy to spot because of the color (Gray or black). As woodworkers, these are great for sanding and polishing finishes. They have super high grits and can be used wet or dry, so when we talk about we-sanding, this is the stuff we’re using.
Stearated: You’ll very frequently hear the term “stearated” being used in reference to sand paper. Basically, this is a chemical treatment that prevents the paper from clogging. Think of it like a coating of soap that stops wood and finish from adhering to the grit. So stearated papers are great for sanding finishes, because the finish dust tends to ball up and stick to the paper.
Closed vs Open Coat: This property refers to the amount of space between the grit particles on the paper. Open coat means the grit is further apart and is less prone to clogging. It also means the paper tends to last a little longer. Closed coat means the grit particles are closer together and the paper can become clogged more easily.
Armed with this terminology, you should be able look at any package of sandpaper and determine how you might be able to use it and whether it is appropriate for your project.
Sanding is nothing more than scratching a surface with grit, right? And its pretty obvious that 80 grit scratches are much deeper than 220 grit scratches. So if you jump from 80 to 220, you’re asking a lot of that 220 grit. In fact, you’ll work harder and go through a lot more paper if you try to remove 80 grit scratches with 220 grit. So it is much more efficient to jump from 80 to 120, and then to 220. Not only will you save time, but you won’t go through quite as much paper in the process. Additionally, you’ll have a much smoother/consistent surface in the end.
This is something we don’t talk about much because most sanders only have one pad available. But did you know that the pad itself can have an impact on your sanding results? For most large or perfectly flat surfaces, you can reach your desired surface finish pretty effectively using a soft pad.
For more delicate pieces, curves or contours, you?re going to want to use a super-soft pad.
For the most delicate of surfaces, or sensitive of curves, you can even employ a cushioned interface pad that eliminates any pressure so you lightly abrade the surface while maintaining a precise shape or profile.
For jobs where a crisp edges are essential, a hard pad would be idea. For instance, when you’re sanding a fairly narrow edge, a soft pad will round over the edges very quickly. But a hard pad keeps the the edge square and doesn’t conform to the edge.
Festool has pads for all of these situations, including a special long life pad that is resistant to high temperatures. Excessive heat can actually destroy the plastic hook and loop material so in a heavy-use or industrial setting, a long life pad can really save you some headache.
Most of you should know that the dust created by sanding is incredibly bad for you. I try to hammer this home every year during safety week. The best way to avoid breathing the stuff is to prevent it from getting into the air in the first place. So the way we do that is by effectively collecting the dust at the source. When you buy a sander, you should absolutely keep an eye out for a dust collection port and instead of just using the collection bag, connect it to a dust extractor.
Aside from heath, there are other potential problems from dust getting in the air. Airborne dust tends to say airborne for a long time. It gets into your tools and eventually, settles into your finish. So if you sand in the morning, you can bet there is still airborne dust floating around when you apply your coats of finish. The end result is more work sanding dust nibs out of your finish.
Now here’s another factor that isn’t discussed very much. You know how when you sharpen your planes and chisels, you have to clean off your chisel after each grit, to prevent contaminating your higher grit stones? The same thing can happen when you’re sanding. Imagine sanding with 80 grit and no dust extraction. The 80 grit dust particles just sit on the surface and can set you back when you begin sanding with the next grit, say 120 grit. The sander is now pushing that 80 grit dust around on the surface and it becomes more difficult to sand efficiently. So if you remove all that 80 grit dust ahead of time, the 120 grit paper is free to do its job.
Check out my book! Finishing: it ain’t over till it’s over. We even have an ebook version available! Written in an entertaining style with a touch of humor, “Finishing – it ain’t over till it’s over” is designed to provide newcomers as well as seasoned woodworkers with the practical information necessary for a relatively trouble-free finishing experience.