How Does
Choosing the Backing
-
The backing of sandpaper can be one of four materials: paper, cotton, polyester or rayon. Paper is the most common of these. However, if the sandpaper will be used in wet sanding applications, it must be coated with a special sealant that will make it water resistant. If sandpaper with a paper backing isn't treated with the sealant, it will crumble. The backing is usually rolled along a conveyor belt in a long strip.
Applying the Abrasive Coat
-
Once the backing is decided upon, it will be coated with an adhesive, called a "make coat" that will make it possible for the "sand" to adhere to it. Once the make coat has been applied, the backing will be turned upside down and passed over abrasive material that is electrostatically charged to the opposite of the backing. In most cases, the backing is positive and the abrasive is negative. The density of the abrasive varies. If the abrasive covers no more than 70 percent of the surface area of the backing, this is called an open coat abrasive. If it covers more than that, it is called closed coat abrasive. Open coat abrasives are more flexible, which makes them suitable for sanding belts and manual sanding. Closed coat abrasives are more suitable for orbital sanders.
Applying the Size Coat
-
After the abrasive coat is applied, the sandpaper goes through a drying tunnel or is air dried. Once it is dried, the size coat will be applied. To do this, a very thin layer of adhesive is applied over the abrasive coat. This is the coat that determines the grit size. Larger particles are embedded for lower grit numbers. For example, sugar-sized particles are around 300 grit, while flour-sized particles are around 2,000 grit.
Preparing the Sandpaper
-
Once the size coat is applied, a sealant coat will be applied. This coat stops the abrasives from falling off during the rolling, shipping and processing of the sand paper. Once this is applied, the sandpaper is flexed by a machine to help with the processing because when the sandpaper comes off the production line, it is too stiff to go through the processing and cutting.
Processing and Cutting
-
After the sandpaper is flexed, it will be placed onto machines that will prepare it for the cutting process. During this time, adhesive will be applied to the back of the backing and a protective sheet applied if the sand paper if needed. The method of cutting depends upon the type of product the sandpaper will become. For sanding belts, the paper is cut into strips. If the sandpaper is used for an orbital sander, a punch cutter will cut the circles out. Sandpaper for manual sanding is cut into squares or rectangles.
eHow Article: How Is Sand Paper Made?
