|This article is about the current version of DF.|
Soap is a particularly useful type of bar used for personal cleaning, which increases happiness ("recently took a soapy bath") and lowers the chances of an infection in case they are wounded, and for cleaning wounds in hospitals, preventing infections from developing. It is thus a vital commodity in dwarven health care, and one not traded in caravans: you're going to have to make some soap yourself.
Soap is made of two components, lye and fat (either tallow or oil), and occupies a dedicated workshop, the soap maker's workshop. It thus has a somewhat complicated production process; lye must be processed at an ashery from ash, which in turn must be burned at a wood furnace from wood logs that must first be cut down. Tallow is rendered from fat from butchered animals at a kitchen, requiring either livestock or hunting activities, while oil must be pressed from seeds or rock nuts at a screw press, which first requires gathering up or growing crop and then processing them at the farmer's workshop. One unit of tallow or oil plus one of lye creates a single bar of finished soap.
Dwarves do not require soap to clean contaminants such as mud and blood from themselves - if necessary, they will use murky pools, artificial pools of water, brooks, or a well. However, using soap will often generate the happy thought "recently took a soapy bath". It is possible to construct bath-houses (rooms containing pools of water, a soap stockpile, and perhaps a few nice statues) so dwarves living deep underground need not venture to dangerous cave pools or surface brooks to clean off a little mud or bloodstain. For cleaning wounds and preventing infection after surgery, however, hospitals should be kept stocked with a small amount of soap. Soap will get used up as dwarves wash themselves; the current rate seems to be 1/10 a bar per washing, so each bar lasts quite a while.
Dwarves have an internal "dirtiness" level, which gets lowered when they have a bath, lowered further when they have a soapy bath and slowly builds up over time. This "dirtiness" value is connected to the chance of getting an infection if the dwarf is injured, making soap useful as a preventative as well as treatment.
Soap is stored in bar/block stockpiles with the "soap" option enabled.
A convenient way to keep an emergency stockpile of soap is to use it as a building material for workshops or constructions such as walls. When/if you need more soap, you can deconstruct and get the soap bars back. Since soap in a hospital is reserved for hospital use, this is especially useful in case you start to produce soap before setting up a hospital.
 Low Trade Value
With the introduction of multiple types of oil-based soaps in DF2014, it might seem worthwhile to consider soap as an export commodity. However, soap has no quality modifiers when it is created and is, thus, only as valuable as its base oil or tallow (1☼ for tallow soap, 5☼ for oil soap). Since oils already require three separate jobs to create (plant processing, milling and pressing) and soap require another three jobs (wood burning, lye making and finally soap making), it would be more efficient just to export the oil in a jug instead.
|Primary Industries||Wood - Stone - Farming - Alcohol - Fuel - Fishing - Meat - Metal - Beekeeping - Poultry - Extract|
|Secondary Industries||Armor - Arms - Finished goods - Soap - Glass - Gem - Textile - Ceramic|
|Tertiary Industries||Military - Health care - Trade|