How paper cups are made

A paper cup is a plastic-lined paperboard wall wrapped around a bottom disc that was pressed into a shallow dish.

stations: 7
things upstream: 47
raw sources: 18
steps from the ground: 8

The short version

Cup board is paperboard with a waterproof coating, usually polyethylene. A machine cuts a curved wall blank and a round bottom blank. The bottom is pressed into a shallow tray with an upturned lip, the wall is wrapped around a rod, its seam is heated shut, and the wall edge is folded over the lip and sealed.

Coat the cup board

Paper is made on a multi-ply machine into stiff board and given a waterproof layer so hot or cold drinks cannot soak through. Polyethylene replaced the old clay and wax coatings.

Goes in
Paper Polyethylene
Print the pattern

Designs are printed on the board in long runs using flexographic plates, one for each color.

Goes in
Ink
Die-cut the blanks

One cutter punches out the curved wall blank, shaped like a fan segment. A second cutter punches a plain circle for the bottom.
Press the bottom lip

The circle is pushed through an opening smaller than itself, so its outer edge bends down into a lip. Cup makers work hard to avoid pleats in this lip, because pleats can leak.
Wrap the wall seam

The wall blank wraps around a rod that carries the bottom. The overlapping edges are heated and squeezed together so the plastic coating fuses them.
Fold and seal the base

The bottom of the wall is folded over the lip and pressed against it, sandwiching the lip and sealing the base.
Roll the rim

The top edge is curled outward into a rolled rim, which makes the cup stiffer and easier to drink from.

End of the linePaper cup

Worth repeating

The Dixie Cup was first called the Health Kup, and was renamed in 1919 after a line of dolls.
Early cups for hot drinks were made watertight by dropping clay into the bottom and spinning the cup at high speed, but the drinks tasted of cardboard.
Because cups are lined with plastic, they are hard to recycle with ordinary paper.