Aluminum profiles can be polished by physical or chemical method or by both methods. Chemically treated profiles appear much more bright and smooth than physically treated profiles, but cost much more too.
Physical polishing involves the polishing with cotton, flax or wool cloth, or sometimes with compound process. The polished profiles will then be anodized with normal process. These processes cause little pollution while maintaining a much bright surface than normal silver anodization does. Also they can eliminate the 'extrusion lines' than normal anodization cannot get rid of.
Chemical polishing involves the acid 'bath' process, mainly with vitriol, nitric acid and other chemical. The pollution therefrom is obvious and normally specialized equipment and licence will be required. The ratio of chemical and temperature decide the final outcome of the polishing process. The quality of base metal is also very important for chemical polishing. To increase the brightness, sometimes special aluminum alloy, such as 6463, will be used to obtain 400-700 brightness unit.
To make the aluminum extrusion wtih 'mirror' appearance, both physical and chemical processes will be involved.
In all, as there are some many factors/processes involved in the production of polished aluminum profiles, the cost is much more than normally anodized aluminum profiles. The brighter the profiles appear, the more expensive they will be.