I would like to know the details of the process of manufacturing papier-mache egg cartons and trays.
I’m not unfamiliar with the general concepts of making paper products; pulping and so on.
I have noticed that the trays have a smooth side, which retains the impressions of what appears to be a fine mesh, and a rough side which looks fairly unprocessed; what I specifically would like to find out is whether the pulp is formed onto shaped mesh or whether it comes off the mesh as a flat sheet and is pressed into shape.
Also I would like to know about the method of drying; are the finished products dried naturally, or by heat/vacuum?
I saw something about this long ago. The porous forms are dipped into a vat of paper pulp, then low pressure is applied briefly to the inside of the form in order to “suck” water out of the adjacent pulp so that a layer of the desired thickness builds up. I would imagine that the forms then go to a drying oven, but that I don’t remember exactly.
It’s vaguely similar to slip-casting of clay objects, where liquid clay is poured into a dry mold and then poured out again. The dry mold “sucks” water out of the clay, and a hard layer builds up.
This company dips moulding dies into the pulp and applies vacuum to make the product.
“The wet product is placed on a conveyor and sent through a drying tunnel (often gas fired).”
They have a few pictures of pulp moulding machinery here.