Having worked in manufacturing processes over the years (albeit accounting) I always found going through the processes interesting. Sugar process in the 80's where I worked, when they first started testing flavoured syrup, stripping cane down and extracting the sugar, a big plant close to home.

During the 90's and early this century (sounds strange) worked in paper making, the liquid to bind different papers together print, notes for banks etc. Also managed a trip through a couple of paper mills, so yes I found this super interesting.