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Technical Education
By Curtis Hicks
Two of the most common grains used to sand and finish wood are Silicon Carbide (S/C) and Aluminum Oxide (A/O). Silicon Carbide is an extremely hard grain. The hardness of Silicon Carbide is second only to a diamond, according to Mohs hardness scale as S/C has a hardness of 9; a Diamond has a hardness of 10. Even though S/C is extremely hard, it is also very brittle which results in the grains fracturing at a quicker rate than A/O grains. The S/C grains, however are very friable, meaning they resharpen each time they fracture to expose a new sharp grain. The grains also break down very consistently. Due to these characteristics, S/C is often used for the final finish of wood and, most commonly, between coats of finish. Even though the life of the grain is compromised due to the quick breakdown of the grain, it does present a very fast cut with a less likely chance of sanding through the finish coat.
Within the Aluminum Oxide range, there are many different types of grains with the most common types being white, pink and brown A/O. Uneeda Enterprizes employs the use of all three depending on the product and grit. Brown A/O is the most durable where White A/O is the least durable but will yield the finest finish due to the rate at which the grains re-fracture. Many times White A/O can leave as good a finish as S/C yet will yield more abrasive life.
In addition to these four basic grain types there are heat treatments, ceramic coatings and other features that can be added during the grain manufacturing process that also differentiate the grains.
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Pink Aluminum
Oxide |
White Aluminum
Oxide |
Brown Aluminum
Oxide |
Silicon Carbide |
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