Blast furnace

Blast furnaces are buildings obtained in the early game used to create iron and coal by consuming wood and iron ore. Later on in the game they can be used to turn sand into glass.

Creation
Blast furnaces are unlocked after buying your first mine. Your first blast furnace costs 200 money and 50 stone. The cost for subsequent purchases is increased by 1.2x for both money and stone. i.e. 1 furnace 200 money 50 stone 2 furnace 220 money 60 stone 3 furnace 242 money and 72 stone. Also at certain higher levels of prestige you can begin to receive blast furnaces for free. This does not affect the base cost.

Production
The base blast furnace produces -5 wood/s, -3 iron ore/s, +1 coal/s, +1 iron/s.

With the Hotter Furnaces upgrade this is changed to -30 iron ore/s, -35 wood/s, +10 coal/s, +10 iron/s.

The Glass furnace upgrade adds -1 sand/s and +1 glass/s

Base
-2.5(.5/wood)/s - 3(1/iron ore)/s + 4(4/iron)/s + 1(1/coal)/s = -.5 prestige/s

Hotter Furnaces
-30(1 iron ore/s) - 17.5(.5/wood)/s + 40(4/iron)/s + 30(1/coal)/s = 22.5 prestige/s

Glass furnace
-30(1 iron ore/s) - 17.5(.5/wood)/s -2(2/sand)/s + 20(20/glass)/s + 40(4/iron)/s + 30(1/coal)/s = 40.5 prestige/s