How toilets are made
Toilets shrink in the kiln, so each plaster mold is deliberately oversized, and it lasts for up to 100 castings.
- stations
- 7
- things upstream
- 5
- raw sources
- 5
- step from the ground
- 1
The short version
Toilets are vitreous china: ball clay, china clay, feldspar and silica in water, poured as slip into oversized plaster molds. After a couple of hours the surplus drains away. The casting is trimmed, dried for 8 to 10 hours, sprayed with glaze and fired for about 40 hours. Leak and flush tests come before the fittings go on.
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Blend the slip
Ball clay, china clay, feldspar and silica are mixed with water into a thick slurry called slip and stirred until free of lumps and air pockets.
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Pour into plaster molds
Slip fills an oversized plaster mold and sits for a couple of hours while the plaster soaks water out of it. The excess is drained. Some plants use high-pressure casting, which is faster and less affected by the weather.
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Demold and trim
The soft casting, now called greenware, comes out of the mold. Workers remove seams and smooth the surface by hand, because at this stage a knock can ruin it.
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Dry the greenware
A dryer at around 90 to 100 °C takes out most of the moisture over 8 to 10 hours, so the piece will not crack in the kiln. Inspectors then mark any damage and sand the surface.
90-100 °C
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Spray on glaze
Spray guns lay about 1 mm of glaze over the dry body, in several passes on some lines. Once fired, that layer seals out stains and bacteria.
about 1 mm
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Fire in the kiln
The kiln climbs to around 1,200 °C, and some makers go over 1,280 °C, across about 40 hours. The clay vitrifies into a waterproof body and shrinks to its final size.
about 40 hours
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Test and fit
Each piece is checked for leaks and flushed. Rough spots are polished, and then the seat and flushing mechanism are added.
Worth repeating
- Slip casting appears to have been reinvented in England around 1745 and became the main technique for sanitaryware by the end of that century.
- Sir John Harington designed a precursor of the flush toilet in 1596, but such systems did not come into widespread use until the late nineteenth century.
- William Elvis Sloan invented the Flushometer in 1906, using pressure instead of a tank.
Back to the ground
Follow every input upstream and toilet starts as these 5 raw sources.
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Sources
Cite this page: "How toilets are made." Assembly Line, 2026-11-03. https://assemblyline.org/make/toilet