I’m sure some of you have been curious about how sandpaper is made, especially those who use sandpaper a lot for their jobs and projects. Sandpaper is used in so many different jobs to provide smooth surfaces and for polishing and finishing. Dating back to the 13th century, “sandpaper” was first used by carpenters in China. I use quotes around sandpaper because they really used a variety of things: sand, seeds, seashells, and other items as abrasive grain in that time period. They used these abrasive makeshift items just how we would use sandpaper – to get rid of unwanted material on a surface with friction and a precise or sharp tool. What is different about the 13th century and now is that we actually assemble sandpaper in order to get the best cut and finishes on projects.
To make sandpaper, the first thing is applying a backing. There are several different backings that are applied to sandpaper that we will touch base on. First, let’s talk about paper backing. Paper backing comes in different weights. There is A weight, C weight, E weight, and F weight – E weight and F weight are usually seen as one category in itself. The A and C weights are used on discs and sheets of sandpaper. So, if you are someone that uses wet/dry sandpaper, the backing on the piece of sandpaper you use is going to be paper. E and F weights are used for belt making. Along with paper backing, there is also a cloth backing. Cloth backing has different weights as well: J weight, X weight, and Y weight. J weight backing is a flexible cotton or polycotton. You may be wondering what the difference is between cotton and polycotton. The difference is that polycotton is waterproof, whereas cotton is not waterproof. X weight and Y weight are a stiff cotton or polycotton; however, polycotton is mainly used. J, X, and Y weights are used for sandpaper belts and sandpaper disc making. While we are on the topic of cloth backing, Aluminum Oxide cloth (X weight or Y weight) can be either open coat or closed coat. The difference between open coat and closed coat is that the grains on the open coat are more spread out and the grains on the closed coat are very tight and close together. With that being said, open coats are good for softwoods so that wood particles have somewhere to go instead of piling up or loading. Closed coats are good for hardwoods or metals because they provide more cut. Now, Y weight, that is polycotton, is always going to be zirconia, silicon carbide, or ceramic. The backings come uncut, so warehouses and factories cut them to the desired size and the grit number will then be printed onto the back. To actually apply the backing, an adhesive like an even coat of epoxy is used along with heat to ensure it will stick.
To apply the abrasives onto the epoxy, a machine is used in order to get an even layer. It is important for sandpaper manufacturers to get an even coat of abrasives because if it is uneven, it can really damage the surface of your job or project. Once the abrasives are added, it is then time for them to bake at a high level of heat. The reason they are baked is to ensure the abrasives are sealed onto the epoxy rather than just sticking to it. After the first coat, another coat is added and baked. The sandpaper is then cut into discs, belts, sheets, and more – so there is a variety of different sandpaper that will work for small or big jobs.
There are different grit sizes, from coarse to fine, to choose from to get the best finish on your project. The lower the number, the coarser the grit and the higher the number the more fine it will be. Make sure to pick a grit size that will be best for your job in order to not get unwanted damage.
Sandpaper is used for so many things in this day and age that you may not even realize such as floors, cars, furniture, doors, painting, nail files, and so much more. Now that we have tools to go along with sandpaper, it makes projects a lot easier. Sandpaper is super helpful and will continue to be forever.