Materials People?

Hi Folks

Bit of an odd story. My Wife has been experimenting with a pressure cooker. I notice these days a lot of food processing equipment is going this way.. Pressure friers and ovens and such to reduce cooking times and energy consumption anyway she had something she cooked that used a cover of aluminum foil and I noticed the edges of the foil were discolored on examining it I found it to be a lot weaker and noticed it was perforated with tiny But randomly shaped holes.

So before I try experimenting I figured I'd ask here about this phenomenon and if anyone know what the cause was and if there Is there a way to do this on purpose in a way that controls the number or size of the holes?

If there was salt on the top of what she covered that could be the culprit. Salt combined with moisture can attack the aluminum oxide and subsequently the base material and heating will accelerate the process.

I used to cover the food with banana leaf so that it absorbs all the heat and it wound make any heat on metal sheet