[Jewelry making - Article 00054] - Re: [Orchid] Using aluminum in jewelry

[Peter W . Rowe]

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>     I don't think skin reactions to aluminum are common, but I have
>     had it happen. The first time I noticed it there was a patch of
>     dermatitis on the back of my hand that wouldn't go away. Took me
>     awhile to make the mental connection, but one day while I was
>     putting my daughter in her car seat I noticed the aluminum catch
>     was rubbing on the exact spot where I had the rash. I've gotten
>     similar reactions since, so I'm a bit more careful of aluminum than
>     I used to be. 

    The thing about aluminum is that it's highly reactive with oxygen
    (and a number of other things too.). But the resulting compounds are
    then very stable. In the case of aluminum, that reactivity forms,
    virtually instantly on contact with air, a rather durable and inert
    film of aluminum oxide (essentially, sapphire, though not quite the
    same structure). The result of that is that your skin is not
    generally in contact with aluminum, but rather the usually inert
    oxide layer. But here's the catch. Much of the aluminum we use is
    anodized. That process makes the oxide layer much thicker, but the
    layer it produces is initially rather porous. That is what allows it
    to be dyed. It is then sealed, often with a salt solution, that
    changes the structure to a mostly non-porous one, sealing in the dye.
    So contact with anodized aluminum is not just contact with aluminum
    oxide. It's also contact with traces of whatever salts may have been
    used to seal it, as well as perhaps contact to some degree with
    whatever dye was used. Even with aluminum that is not specifically
    anodized and dyed, some surface trapping of contaminants may be
    possible, again meaning that contact with the stuff is not just
    contact with aluminum oxide. All of that makes possible the
    instances of dermatitis in some people, and some examples of
    aluminum. Not easy to predict which ones. If you do your own
    anodizing, and seal with just boiling water, and use dyes you know
    are not allergenic, then just maybe you can mostly predict it's
    safety. But it's still not a total guarantee. It's not commonly a
    problem for most people, but perhaps that just makes it harder to
    track down when it IS a problem... 

Peter Rowe

 
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