Glass

Glass is chemistry and furnaces rather than power, so the Known World's is centuries ahead of what the rest of its technology would suggest.

Optical glass

The foundation of the world's medicine. Crown and flint, achromatic pairs, careful annealing, and lens grinding as a respected trade in its own right. Without it there are no microscopes, and without microscopes there is none of what medicine can do.

Vessels and chimneys

Borosilicate for anything that will be heated: apothecary and laboratory ware, lamp chimneys, and the sight glass on every boiler in the world.

Mirrors

Silvered with silver nitrate rather than tin and mercury, so they come out clear and flat and nobody is poisoned making them.

Strengthened glass

Soaked in a hot salt bath so the surface goes into compression. A Clearhold specialty, documented and priced accordingly, and how you get a lamp globe that survives a drop or a sight glass that does not let go when a boiler surges. Thermally tempered glass exists too, quenched with a blast of air from a steam blower.

Plate

Cast, ground and polished, limited in size by the table it is polished on, and expensive. There is no float glass, which would want an industrial tin bath — see The Ceiling — so windows are divided by glazing bars and a single large pane is a display of wealth rather than a building material. A Shining Reach shopfront with four big panes is saying something about its owner.

Who is best at what

Eldershore blows the best colour. Clearhold does the precise and documented work. Forgegate makes everything in volume. Shining Reach buys the large flat pieces and puts them where visitors will see them.