|This article is about an older version of DF.
The Ashery is used for creating potash and lye from ash. This building is necessary if the player wishes to create clear or crystal glass, fertilizer, or soap. This building uses the "potash making" or "lye making" labor.
The "make potash from lye" task will process a single stack of lye from a given barrel and produce one bar of potash. As lye purchased from caravans always comes in stacks of 10, this means the other 9 units of lye are wasted.
"lye" in real life
Lye is made by soaking the ashes in water to extract the water soluble part; the remaining solid ash is discarded by filtering or settling in a barrel and then drawing off the lye from the top. Drying lye leaves potash, unrefined potassium oxide (a caustic alkali), while the active ingredient of lye is potassium hydroxide.
The caustic lye will break down tallow into soap and glycerin. The soap is retained while the glycerin is washed away when rinsing the soap to remove remaining lye.