|This article is about an older version of DF.|
Glass furnaces are used to make raw glass (a gem), blocks, and furniture items. All furniture made at a glass furnace can alternatively be made out of either metal, stone or wood, with the exception of windows, which can be made from gems. Glass furnaces can also make various trade goods, and vials used to make certain extracts at a Farmer's workshop.
Glass furnaces can make goods from green glass, clear glass, and crystal glass. Green glass requires sand, clear glass requires sand and pearlash, and crystal glass requires raw rock crystals and pearlash. Raw rock crystals are a type of gem and are not available in most regions.
Some of the names of glass furniture are different. A glass door is called a portal, a glass coffer is called a box, a glass pipe section is called a tube, and a glass cage is called a terrarium. Also, vials can be produced at a glass furnace, each bag of sand resulting in 3 vials. Vials have the same function as flasks and waterskins, and can also hold extracts.
Glass furnaces are also needed to issue the "collect sand" order. This requires an empty bag, an Item Hauler, and a zone designated for sand collection. As the "Collect Sand" order will prevent other tasks from being started until the sand is collected, it is often wise to build several additional glass furnaces, magma or otherwise, to use for the collection of sand.
Not all maps have a source of sand, but sand may be imported in small quantities. Caravans will also bring raw glass (of all 3 types) for trade, which can be particularly useful for dealing with strange moods.