>Alternatively, though, it might be possible to stiffen the foil by making the equivalent of corrugated cardboard out of it, maybe using aqueous boric acid (US$1.70/kg according to Potential local sources and prices of refractory materials) or borax as the glue. The surface tension of water is ample to hold aluminum foil in place until the water dries.

Hello Amazon? Billion dollar idea here. This needs more attention. You could have fully recyclable aluminum boxes instead of cardboard. Imagine your box supply chain literally being a circle.

I don't know about corrugated aluminium, but aluminium honeycomb is definitely a thing: https://www.easycomposites.co.uk/aluminium-honeycomb

That would be hell on everybody's box-cutters (and fingers). I already cut myself too often on shipping boxes.

Cardboard is very recyclable already.

aluminum foil is generally not something you can recycle. Not that it can't be recyled, but the oxide to pure aluminum ratio is high and so you don't gain much since you need all the energy of refining in the first place to get back to something usable.

Amazon needs stronger boxes than foil anyway. Cardboard is likely best for them.