etch aluminum

My father was approached about doing some kind of etching on aluminum for the outside of a building. This is for the outside of a fire station (6' X
80' in 3' wide panels 1/8" thick).
Me - being the computer person, I did some research about blackening aluminum and ran across an article written several years ago from this newsgroup. The aluminum was dipped in a solution of Nitric Acid, Copper Nitrate, and Potassium Permanganate and water. The reason I looked for blackening aluminum is because I believe there needs to be some contrast for the etching to show up.
With doing large panels, I'd want them to be a consistent color. My dad owns a monument business and so owns sandblast equipment. There is a process of etching which sandblasts a half-tone mask applied to stone. We are also aware of a laser etching process which burns an etch with a laser. The first thing I'm not sure about is how thick this blackening is on the aluminum. So if a laser etch etched the aluminum, would it burn through the blackening? As we are experienced with stone but not with aluminum, we need any kind of basic advice which you can offer.
Is this feasible?
Is there a better way that you are aware of, or a place you can lead me?
thanks, James Deckert
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James Deckert wrote:

The thing I know about laser etching is: You apply some etch (from a spray can) and go over it with the laser. It gets black where the laser "etched". It doesn't make a recess, it only blackens the alumin(i)um. It's used for small-run front-panels in electronics. You might get more info contacting a front panel mfg.
Nick
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Jim, seriously this raises the question of "how black" do you want. Do you want to achieve a true "optical black finish", or simply a black disfusely reflective surface? Both anodizing and chemical methods exist to accomplish the optical black finish on aluminum, but I doubt that this is what you want to do. Still, one place to start looking is likely here:
http://www.finishing.com/385/33.shtml
Not that this particularly post is particularly informative for your purposes, but the website is quite highly respected for the quality of its information and discussions, and may be a good starting point.
Just as an aside, if you are already familiar with "optical black", unless you want the firehouse to become nearly covert and almost invisible, that's likely not the finish you are looking for. Still, you may find something useful for your application on the website. Fortunately, there are variations of the optical black theme and technology, which range from close to near totally reflectionless surfaces, to the lusterous back finish on some high end cameras.
Harry

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James Deckert wrote:

Why not black anodize the panels, sand blast clear areas, and then clear anodize or protective clear coat.
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