- Polishing compounds can be used to polish machined aluminum that appears to have no residual texture left over from the machining process. They are ineffectual on brushed aluminum. Polishing compounds work because the liquid or paste carries microscopic bits of abrasive material that slowly smooth out the surface of the aluminum. There are a variety of polishing compounds available that will polish aluminum, ranging from scratch remover to haze polish, and several intermediate grades of polish in between. Using polishing compounds is as easy as choosing the right compound and then rubbing it on the machined aluminum with a buffing cloth.
- Sandpaper is a form of polishing media that is useful if the machined aluminum you are working with has a pronounced texture to it. In general, sandpaper rated at a greater grit than 800 works well for polishing machined aluminum. When working with sandpaper, it is important to remember that adding water between the aluminum and the sandpaper acts as a lubricant, effectively increasing the polishing ability of the paper. If, for instance, you polish a piece of aluminum with sandpaper up to 3,000-grit paper, simply sprinkling a little water on the aluminum before continuing will increase the grit of the paper you use.
- Machined aluminum that is to be polished to a perfectly flat surface should always be lap polished. A lap polisher is a machine that uses smooth abrasives and polishing compounds to achieve a perfectly smooth finish that isn't possible when hand polishing machined aluminum. The drawback to lap polishing is that generally, only one surface of the machined aluminum part can be polished at a time, then the material has to be turned to perform the polishing on another side. Lap polishing is also less effective at polishing complex surfaces and concave surfaces.
- Media blasting to polish machined aluminum picks up where lap polishing leaves off. While this form of polishing is not very good for polishing flat surfaces intended to have a mirror finish, it is very good for polishing complex surfaces and concave surfaces. In order to media blast to polish aluminum, it is best to use the smallest plastic media you can find. Glass and sand are too harsh and will actually dull the surface that you are attempting to polish.