WATER  SOLUBLE  SOILS Water  soluble  soils  are  such  substances  as sugar,  starch,  gums,  salt,  flavoring  agents,  and syrups,  as  well  as  a  wide  variety  of  substances generally  found  in  such  foods  and  beverages  as mustard,  catsup,  soups,  and  soft  drinks.  Per- spiration  stains  are  also  included  in  this  category. These   types   of   soils   are   removed   during   the normal  laundering  process. INSOLUBLE SOILS Insoluble  soils,  substances  that  are  not  soluble or dissolvable in either water or chemical solvents, are the materials most commonly found in fabrics and  constitute  the  bulk  of  the  soils  removed  in the  laundry.  Included  are  earth,  concrete  dust, sand,  carbon,  ashes,  lint,  hair,  cosmetics,  and dandruff.  These  types  of  soils  are  usually  less visible than oils, greases, or food stains, but they contribute  greatly  to  fabric  damage  due  to  fiber abrasion. Most   insoluble   soils   are   readily   dispersed during  the  wash  cycle,  but  their  complete  removal may  prove  more  difficult.  Such  soils  are  some- times  redeposited  on  the  garments  during  the laundry   process,   a  condition  that  can  cause “graying”   of   the   fabric. SPECIAL SOILS Special soils are insoluble in either water or laundry chemicals. They may be removed partially or entirely using spotting operations. These soils include  nail  polish,  paint,  ink,  various  kinds  of adhesives, and so forth. Spotting operations are discussed  in  the  dry-cleaning  chapter. THE  WASH  WATER Water  is  the  most  important  item  used  in  a laundry. Not only is it needed in quantity, but the quality of water used has an important effect on the washing process. At sea, where quantities of suitable wash water are  always  subject  to  greater  limitations  than ashore,  you  may  not  always  have  enough  soft water  available.  To  conserve  fresh  water,  you  may be required to use seawater. When  water  comes  from  clouds  as  rain  or snow, it picks up carbon dioxide gas. As the water seeps through the ground, the carbon dioxide gas dissolves  limestone  and  some  other  substances, and  the  water  collects  calcium  and  magnesium salts. The salts are in the form of bicarbonates, chlorides,  nitrates,  and  sulfates.  The  kind  and quantity of these substances are determined by the soil the water passes through. Water that contains an appreciable quantity of salts is HARD water. SOFT water is water that has not picked up salts from  the  earth,  or  water  that  has  had  these substances  removed  or  neutralized.  Since  seawater contains the concentration of salts, it is the hardest of  all  wash  waters. TYPES  OF  HARD  WATER In laundry terminology, hardness in water is the  power  to  kill  soap.  When  soap  is  added  to hard water, the calcium and magnesium salts in the  water  combine  with  the  soap  to  form  insoluble lime soaps. These soaps then unite (precipitate) in  the  form  of  a  sticky,  insoluble  deposit.  This reaction  kills  the  soap  and  makes  it  useless  for washing, and the sticky deposit traps dirt and puts it  back  on  the  fabric  in  the  form  of  scum.  If  no dirt is present, the scum is white and is seen as a  film  on  the  clothes. There  are  two  types  of  water  hardness: 1. Temporary hardness—Water that contains calcium  and  magnesium  bicarbonates  is  called temporary  hard  because  these  elements  can  be removed by boiling. Scale on the inside of steam kettles and steam boilers is due to the precipitation of insoluble carbonates as the hard water is boiled. 2. Permanent hardness—Water that contains calcium and magnesium chlorides that are NOT affected by boiling is said to be permanently hard. Permanent  hardness  requires  special  treatment with  chemicals  or  by  distillation. WATER  SOFTENING  METHODS The  methods  generally  used  to  soften  water are known as the base exchange and distillation. The base exchange method softens water when the compounds  of  calcium  and  magnesium  in  the water  are  exchanged  for  compounds  of  sodium which  do  not  cause  hardness. The distillation method softens the water when it is boiled and the vapor is cooled by running it through  pipes  immersed  in  a  cold  solution  to reconvert it to water. The distillation method is used to make seawater usable for a ship’s boilers and other shipboard uses. Seawater distillate is not  pure  water,    but  it  contains  only  about 1/20,000  of  its  original  concentration  of  salts. 5-14