December 17, 2014

All About Sanding. The challenge of sanding is sanding. No one likes it, and yet if you’re a woodworker or a DIY-er, there is no getting around it. And there lies the rub. Interestingly, the true testament of a sanding job done well is that no one notices it. That’s right! A great sanding job is met by silence. No one will ever say, “Wow, I love what you did with the sanding.” However, you will know how you did, and you can take pride in a project piece done well. And even though sanding isn’t the most gratifying experience, the good news is, it goes a lot easier and more quickly when you use the proper sandpaper with the right abrasive while working on your wood or diy project. And so, here we will demystify this process for you! Never again feel intimidated by instructions which read simply  “and then you sand it.”

So what is sanding? Sanding is the process of removing the top surface of a material by using the cutting action of an abrasive. The objective of sanding, mostly, is to remove flaws and imperfections from a work piece, however, there are times when polishing or dulling a surface is the objective.

Types of  Popular Sandpaper (Sheet Abrasives)

Aluminum Oxide: Though aluminum oxide is the most common abrasive used in woodworking, it has an uncommon characteristic, which is the ability to continually renew its cutting edges simply by sanding. The term is called “friability”, and what that means is that the heat and pressure created by sanding causes the grit to fragment and break away, creating more sharp edges. Aluminum oxide can be used on surfaces other than wood, such as plastics, metal and paint. It’s a good choice because it stays sharp, is long lasting and by far it’s the most economical of the four sheet abrasives mentioned in this article.

Advantages: Durable, friable, ideal for high-speed sanding, and economical

Disadvantages: Can gum up when sanding soft, resinous materials

Garnet: Garnet lacks toughness and dulls fairly quickly. What it has going for it is its softness, and this quality produces a very fine, really smooth finish. In addition, if you are using a random orbit sander, it is less likely to score the wood with pig tail scratches. It’s a nice choice for final sanding of your wood project.

Advantages: Good for woodworking and moderately priced

Disadvantages: Not recommended for sanding metal

Ceramic: Ceramic is an extremely robust, durable material which does not dull quickly; it’s best used for aggressive stock removal like shaping wood and leveling uneven planks, and it is also ideal for removing paint. Ceramic tends to be available mostly in coarse grit belts, which can be very pricey.

Advantages: Extremely durable, best for heavy stock removal

Disadvantages: Grit size is limited to mostly coarse, and it is expensive

Silicon Carbide: Easy to spot because of its distinctive bluish gray or black iridescent color. Silicon carbide is perhaps the hardest sandpaper available. It is this characteristic which makes it a superior choice for cutting hard surfaces such as paint, plastic, glass, metal and even stone. It’s also a good choice for rubbing out finishes like lacquer and shellac. In addition, silicon carbide is suitable for wet sanding.

Advantages: Cuts extremely well, is suitable for sanding a variety of materials, is the hardest, sharpest sandpaper available

Disadvantages: Breaks down quickly when sanding harder material

Less Popular Abrasives

Flint: Largely, flint has a poor bite and is not a very durable abrasive. It can be used in leather work, paint removal and some woodwork.

Emery: Good for metal polishing, however the quality is not suitable for material removal or wood use.

Pumice: Powdered volcanic element, frequently used to tone down a glossy surface or finishes.

Rottenstone: It is much finer and softer than pumice, and is used in combination with water, oil or solvents to yield a satin finish on wood.

Steel Wool: Steel wool is not technically an abrasive, however, it does carry similar qualities in its ability to remove old finishes and smooth rough surfaces.

Sandpaper Coatings Explained:

Grit: The grit is the size of the particles that are glued to sheets of backing. Backing materials are paper, cloth, boPET, fiber or a combination of both paper and cloth, or cloth and fiber

Stearated: This is sandpaper which is chemically treated with stearic acid to prevent the paper from clogging with sawdust particles during the sanding process.

Open Coat: Open coat means the grit is further apart, covering 50 to 70 percent of the surface backing which makes it less prone to clogging. Because open coat sandpaper is less likely to clog, it remains effective longer in it’s ability to bite the surface area and remain sharp.

Closed coat: Closed coat means the grit particles cover the entire face of the backing material. This enables it to remove material faster than open coat, because there are more abrasive particles per square inch of surface area. Closed coat sandpapers do have a tendency to become clogged more easily, which can reduce their life. Overall, closed coat sandpapers are the preferred type because they tend to yield a better finish than open coat sandpapers.

The most efficient means of sanding is a progression through varying grits. You start with a coarse enough grit of sandpaper to cut through and remove the flaws and imperfections speedily, then sand out the coarse-grit scratches with finer and finer grits until you obtain the evenness and smoothness your project requires. Reference the guide below.

by See Jane Drill, Copyright 2014, All Rights Reserved