How coffee mugs are made
Each plaster mold can press about 1,000 mug bodies before it wears out, and a press makes handles six at a time.
- stations
- 8
- things upstream
- 2
- raw sources
- 2
- step from the ground
- 1
The short version
At the East Fork pottery, clay is pushed through a pug mill, pressed into a spinning plaster mold and shaped inside by a steel die. A hydraulic ram press makes the handles six at a time, and slip glues them on. After drying, each mug gets a first firing, a glaze dip and a second firing. Many factories slip cast instead.
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Pug the clay
Clay goes through a pug mill that squeezes out air bubbles and extrudes long, smooth cylinders called pugs, sized for one product.
Goes in -
Press the body
A machine measures a slug of clay and presses it into a plaster mold. As the round table turns, each mold meets a steel die that forms the inside and removes excess clay. Other plants pour liquid slip into plaster molds instead, and the plaster draws out the water.
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Dry and trim
Dryers under the molds firm the clay enough to handle in around 15 minutes. Each body comes out, and hands clean up edges and crevices.
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Ram-press the handles
Hydraulic pressure pushes clay into a plaster die that forms six handles at once. Once dry enough, they are cleaned by hand and sized on a taut wire cutter.
Goes in -
Stick on the handle
Watered-down leftover clay, called slip, is dabbed on the body. The spot is scored rough, and the handle is pushed on firmly enough to leave no gaps.
Goes in -
Fire the first time
After a few days on carts the bone-dry pieces are wheeled into the kiln for their first firing, then unloaded once cool.
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Dip in glaze
A worker fills the mug with glaze and pours it out with a circular turn of the wrist, then dips the outside. A spongy conveyor belt wipes the rim clean.
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Fire and finish
A second kiln firing melts the glaze and changes its color. A machine then brushes off any stray debris before final inspection.
Worth repeating
- A typical mug holds approximately 250–350 ml, and anything much larger is usually called a tankard.
- The bottoms of mugs are often concave so that less of the base touches the table, which also leaves a ring stain.
- During World War II the US Navy chose a thick white porcelain mug from Victor Insulators, a maker of high-voltage insulators.
Back to the ground
Follow every input upstream and coffee mug starts as these 2 raw sources.
Keep walking
Sources
Cite this page: "How coffee mugs are made." Assembly Line, 2026-11-03. https://assemblyline.org/make/coffee-mug