What was that all about ? Somebody had to think about it for two and a half years? First time I've ever heard the word, chutzpah. Some kind of insult, I guess. In any event, museum display personnel and big pro picture framing houses came to me for informed advice for several decades, which was surely not pickled chutney. I'm not trying to win anything. I was paid for that kind of thing. The kind of aluminum plate sold for picture mounting is anodized to begin with, or otherwise permanently coated; it's not raw aluminum, which I assume anyone seriously trained in conservation would already know. My main objection to aluminum is that it is very thermally conductive, which means it should be additionally backed with something like foamboard just for insulation sake with respect to diurnal or seasonal temperature shifts.