An early experiment with etching into aluminum with copper sulphate.
To make etchings from aluminum plates is to abandon many of the advantages of the medium; etching in copper or zinc permits incredible precision and lines of such fineness they could never be produced with a pen. Moreover, both metals are of sufficient hardness that large numbers of proofs can be pulled without significant distortion of the design.
But the reaction of copper sulphate with aluminum is far more violent than those that occur with zinc or copper. Lines become blotted and uneven, while open surfaces are pitted and moon-like. These take ink well, but delicacy is impossible. Worse, the softness of aluminum means the proofs will loose quality quickly.
On the other hand, aluminum is light, easy to manipulate and relatively cheap. And the roughness of the etching process produces a crude and spontaneous effect that I like a lot.