You can’t wash cardboard.
I work in a cardboard box factory. Largely, as one might expect, we make cardboard boxes. But we also make cardboard inserts that go in boxes to hold products into place, and we make the little cardboard circles that go under frozen pizzas.
The sheet of cardboard that will become a cardboard pizza circle must travel in a truck for quite some distance from the corrugator from which we purchase our cardboard. Then, it is taken off the truck and loaded onto a conveyer belt by a fork lift. The fork lift guy (or gal) cuts the plastic bands that hold the stack of cardboard together, then removes the top sheets that are full of dirt and dust from the journey in the truck.
Once thus prepared, the stack of board is fed onto the “prefeeder”. This is just another conveyor belt which takes the stack bit by bit and spreads it out so it’s easier to see any damaged or warped board so it can be removed. By hand. That’s my job.
Then, the board gets stacked bit by bit into the “hopper”. Metal tampers push against it at regular intervals, squaring it up and making the stack nice and even. The bottom sheet of the stack gets pulled into the machine that has a big wooden “die cut” screwed onto a big metal cylinder which spins around rapidly. The cut has little knives on it which are deceptively sharp. Sometimes, if you bump against one while screwing it on, you’ll bleed a little and not even notice.
These knives cut the board into whatever shaped is desired. In the case of pizza circles, it cuts out circles. The extra bits of board fall onto a scrap belt that clears the waste away.
The board is big enough that four 12-inch circles are cut side by side from one sheet. However, they never get cut out entirely; they’re still connected just slightly at the edges. So, they have to be separated by hand. Then, they have to be packed in stacks of 50 into boxes, by hand.
The same hands of my coworkers who, I’ve noticed, never wash those hands after using the restroom.