Common Defects: Etch Non-Uniformity
Both chemistry and metal quality can affect gloss uniformity. It is common to see banding on flat and curved surfaces along extrusion weld lines and opposite flanges. Visible ridges or die lines are also common. Occasionally the etched surface takes on a grainy, or galvanized appearance. All these defects are due to metal quality and/or extrusion practices. Some proprietary etch chemistries are more forgiving to these metal issues than others and are therefore worth trying, but as a general rule, a slower etch with highest possible content of aluminum will give better result than a more aggressive etch.
Etch transfer staining is covered under Stains.