Everyone seems to understand the basic steps . i.e
1) - 200 - 250 grit paper to remove scratches and oxidation, or alternately glass peening.
2) - 300 - 400 grit to remove the paper scratches of the first sanding
3) - 800 - 1000 grit to remove scratches of previous step and to prepare surface for polishing
4) - optional step: 1500-2000 grit to further prep for polishing
5) - red rouge to remove paper scratches
6) - white rouge to polish
7) - wax to fill and preserve, or in lieu of wax, application of clear polyurethane able to stick to smooth aluminum.
Technique is also important. From my own experience and research, the way to a mirror finish ...
1) Every step must fully remove the imperfections at that level. The next step will not do it, if the current step hasn't done it.
2) Its almost impossible to overheat aluminimum if hand polishing, but it is possible to overheat using a high speed polisher, or to score the metal much too deeply. Slow down that electric buffer for a better result.
3) Wash the piece and your hands between steps. Do not keep the papers, cloths, pads, or rouges in contact with each other. Otherwise, the grit from the previous layer will contaminate the current step causing scratches that are too deep.
4) When removing imperfections, don't use circular strokes. Scratches should all be in the same bi-direction. Keep strokes short. Long (over 3") strokes will deepen scratches. Circular strokes also cause the depth of cut to vary.
5) Using a lubricant, such as water, turpentine, or mineral spirits will speed up the removal process in one or both of two ways; by suspending residue and hence removing the buildup of residue in the paper and on the surface, and/or by chemically binding with the metal oxides to make them harder (alum oxide is much much harder than alum powder). Denatured water is safest lubricant and will reduce the risk of scouring the metal.
6) The scratches of one step should be perpendicular, or close to perpendicular, from the direction of the previous step. This way, you can see when all previous scratches have been removed.
7) In the first polishing step, rouge should be applied with pressure at the beginning of the circular stroke. This cuts deeper, and essentially removes any remaining paper scratches. Care must be taken to remove all red rouge before the oxide is suspension begins to scratch the metal again.
8 ) In the final polishing step, white rouge should be applied with pressure at the end of the circular stroke. This essentially removes polish with each stroke. Once a pad or cloth is greyed with aluminum, it will begin to scratch the surface. Aluminum is very soft. Even cotton will scratch aluminum if too much pressure is used.
9) The final preserving layer is optional. A natural wax, such as carnuba can fill in microscopic scratches left by the polishing pad to make the surface even smoother, as well as helping to prevent oxidation. Did you know, that the smoother the surface, the slower it will oxidize?
