Date Uploaded: March 14, 2003, 6:23 pm
Last Edited: August 7, 2012, 5:52 pm
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Permanganate Coloring of Aluminum
Article © MAIL User: Drax
Target metal: Aluminum
Target colors: Various dark shades, gold
One way to darken your aluminum is by using the recipe listed in this section. All of the ingredients needed for this mixture are strong oxidants. Be especially careful of the nitric acid, and watch out for the potassium permanganate -- it's a purple solid that will stain *everything*. I ran across this recipe on the web, but I don't have the link at the moment; I'll try to find it.
To make the needed solution, mix the following together:
750 mLs Water
5 mLs Nitric acid
25g Copper Nitrate (CuNO3)
10g Potassium Permanganate (KMnO4)
Once all mixed together, add enough water to make 1L total. The solution should be dark purple.
You *can* heat this mixture slightly (75F), but do NOT bring to a boil.
Method of use: simply place your aluminum item into the solution. You can check on the progress, but typically the longer you leave it, the darker it gets.
Colors range in various shades of brown, including a very dark shade for long times. With a weaker solution (one that I had used a bunch) I managed to achieve a golden-yellow, but that is less reproducible.
Workability: the coloring is very secure. It can still be scraped off, but takes a lot of work to do so. This may still work best on a finished piece, but should stand up to a reasonable amount of jostling.
The solution would be fine for coloring separate rings or a final piece.
The picture shows an aluminum ring on the left. The middle three show the various shades of brown possible, while the final ring on the right gives an example of the yellow.
Original URL: http://www.mailleartisans.org/articles/articledisplay.php?key=131