Here's a production methods mystery, albeit one we think will soon be solved by one of you.
On the Discussion Boards, a Core77 reader asked how a hot water bottle is made. A couple of votes came in for slush molding, which is like rotational molding without the spinning; the mold heats up, vulcanizing whatever part of the liquid rubber inside comes into contact with it, and leaving the stuff in the middle, well, slushy. You then pour the slush out and you've got your hollow bottle.
However: How the heck is this threaded insert added?
Then, like the rubber, the plot thickens: Our trusty Board Moderator LMO submitted this photo of that very bottle being produced by B.F. Goodrich in 1939:
Looks like it isn't slush molding at all. And if we zoom in on the photo, we can see the frying-pan-shaped mandrel that forms the negative space of the bottle inside the mold:
Which beg the questions: How the heck does the worker get the mandrel out of there?
Is it actually possible the bottle has that much flex? What about the threaded insert? And most importantly, how did Sean Penn travel back in time to work in a B.F. Goodrich factory?
Due to our deep readership, we know it's just a matter of time before someone with direct experience sounds off on how this is all accomplished (except for the Sean Penn time machine part). In the meantime, you may be wondering—where did this awesome and high-quality image of a 1939 manufacturing facility come from, and are there more like it? Stay tuned.