What type of material are you sanding?

One of the most important factors to consider when choosing the proper coated abrasive product for your needs is the material that you will be sanding. This is because every material – whether a species of wood, type of metal, or even solid surface, stone or fiberglass – has different physical properties that will influence factors such as tendency to load faster, the need for more or less pressure when sanding, the hardness of the material and how that will influence friability of the grain, the appropriateness for wet sanding and so forth.

In general, the goal with sanding is to produce the least amount of heat possible. Doing so will result in not only a better finish, but also a longer lifespan for your abrasives – and therefore a lower cost for supplies. Knowing the properties of the material will help you optimize this.

Sanding Softer Materials

When we discuss the softness/hardness of a material we are sanding, what we are really discussing is the susceptibility to heat/melting, as the friction from sanding will generate heat. This heat will then cause the resins in woods, or metal, paint/finishing products, and glue to melt and become gummy/sticky and stay on the sandpaper – along with the sanding dust and any other stray particles.

For this reason, when sanding these materials, it can be helpful to choose products that would have a semi-open or open coat, stearation, and the proper grain type for the application/material. However, if you are in the finishing stages, a closed coat will produce the most even scratch, so you may want to consider that, depending on your goals – for instance, if you are painting the surface, the scratch will be less evident than if you are polishing metal or using stain on wood.

When sanding softer materials, as well as lacquers, paint/primer, and fiberglass, aluminum oxide is often a good choice because it requires less pressure and does not need as hard of a surface to crack and become sharp again, whereas both ceramic and zirconia both require a very hard surface to activate the friability – which may cause them to “plow” through the material, rather than produce a nice cut – making them more suitable for rougher sanding applications.

Sanding Harder Materials

On the other hand, when it comes to sanding harder materials, these will require a sharper grain and likely more pressure. Since they have a higher melting point, quick loading will be less of an issue, but there is always some amount of loading when sanding, since you are producing waste material.

When sanding glass, stone or marble, silicon carbide is the only grain that will work on these materials. Silicon carbide will also work well for drywall, MDF and cork.

When doing a lot of rough sanding of metal, stainless steel in particular, choosing zirconia or ceramic may be your best bets for longevity, in spite of a potentially higher initial cost – as the grains are very long lasting. However, these grains may only available in coarser grits, so if finishing is required, you will have to change to another abrasive – such as silicon carbide for polishing harder metals.