Assembly Line

Kiln firing

A shaped mineral body is heated until its particles fuse, turning something crumbly into something hard and permanent.

33 lines that use it

Alumina 6 stations · 4 raw sources Brick 7 stations · 2 raw sources Bronze statue 7 stations · 9 raw sources Carbon dioxide 5 stations · 6 raw sources Cement 7 stations · 3 raw sources Ceramic 6 stations · 4 raw sources Ceramic floor tile 6 stations · 19 raw sources Chromium 6 stations · 13 raw sources Coffee mug 8 stations · 2 raw sources Digital thermometer 7 stations · 26 raw sources Dinner plate 8 stations · 2 raw sources Ferrite 6 stations · 6 raw sources Germanium 5 stations · 6 raw sources Gold ring 8 stations · 12 raw sources Indium 5 stations · 4 raw sources Indium tin oxide 7 stations · 15 raw sources Iridium 6 stations · 8 raw sources Magnesium 5 stations · 4 raw sources Manganese ore 5 stations Neodymium magnet 8 stations · 6 raw sources Pencil 8 stations · 24 raw sources Petroleum coke 6 stations · 1 raw source Platinum 6 stations · 6 raw sources Porcelain 6 stations · 11 raw sources Quicklime 6 stations · 2 raw sources Roof tile 6 stations · 2 raw sources Soda ash 8 stations · 9 raw sources Spark plug 8 stations · 16 raw sources Stained glass 10 stations · 24 raw sources Stoneware pottery 7 stations · 4 raw sources Synthetic graphite 6 stations · 2 raw sources Toilet 7 stations · 5 raw sources Tungsten carbide 5 stations · 11 raw sources

What it looks like on the line

  • Ceramic floor tileFire in the kiln. Tiles roll through a long kiln that climbs gradually to full heat. The body hardens and fuses, and the glaze melts and bonds to the surface.
  • Neodymium magnetSinter into dense blocks. The pressed powder is heated until the grains fuse into a dense solid block without melting the whole mass.
  • ChromiumRoast the ore for pure metal. For metal free of iron, chromite is heated in air with calcium carbonate and sodium carbonate. The chromium turns into a soluble form, and the iron becomes stable iron oxide that stays behind.
  • PorcelainFire the biscuit. Modern porcelains are biscuit-fired at around 1,000 °C. The first firing firms the ware enough to be handled and dipped in glaze.
  • Manganese oreSinter the undersize. Pieces too small to use directly can be agglomerated by sintering, which binds them into larger lumps.
  • BrickFire in a tunnel kiln. Bricks ride slowly through the kiln on conveyors, rails or kiln cars, so every one sees the same heat. Soft-mud bricks are fired at 900–1,000 °C. The finished color depends on the clay chemistry, the temperature and the kiln atmosphere.
  • Soda ashCalcine mined trona instead. Near natural deposits, such as the Green River beds in Wyoming, miners dig the mineral trona and heat it to get sodium carbonate directly. It skips every station above.
  • Indium tin oxideSinter the plate hard. These oxides resist sintering. In ordinary air firing, the plate reaches only about 60 to 70% of theoretical density, and a low-density target sputters slowly and sheds dust. Hot pressing reaches about 94% but costs far more, and one patent uses pressurized oxygen instead.
  • Digital thermometerFire the bead. A kiln sinters the pressed shapes so the grains fuse into a hard ceramic. Fine adjustments in the firing control the resistance.
  • Synthetic graphiteBake the blocks. The blocks are baked slowly in a furnace for weeks, which turns the pitch into hard carbon. They are often soaked in more pitch and baked again to fill pores.
  • ToiletFire 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.
  • Tungsten carbideSinter until the binder melts. The part is heated until the binder turns liquid while the carbide grains stay solid. Grains pull together into a dense, tough composite.