iron and other metallic salts that cause rust or a yellow  discoloration.    If  left  in  fabrics  these chemicals   cause   odors   and   discoloration   after drying. Another  reason  for  using  a  sour  in  the  last rinse  is  that  it  removes  sodium  bicarbonate,  which is   normally   in   the   rinse   water.   Even   though other  chemicals  may  have  rinsed  out,  sodium bicarbonate remains. It is not injurious to fabrics in  itself,  but  when  subjected  to  the  heat  of flatwork  ironers,  presses,  or  hand  ironers,  it  is converted  to  sodium  carbonate  which  is  quite alkaline and in sufficient concentration can cause injury  to  fabrics. Souring also decomposes any oxidizing bleach left  in  a  load,  prevents  discoloration,  and  helps to sterilize the clothes. In addition, sour sets acid dyes   often   used   in   bright-colored   fabrics   and preserves the tensile strength of fibers. Laundry sour  also  removes  rust  stains. There  are  many  different  laundry  sours  of varying  strengths,  including  acetic  acid,  fluorosilic acid,  hydrofluoric  acid,  and  several  types  of fluoride  (ammonium,  sodium  acid,  and  sodium silico).  Fluoride  is  generally  used.  The  sour required  for  use  is  combined  in  the  powdered  form with  powdered  blue  (NSN  7930-00-205-2882). STARCH Starch  is  applied  to  wearing  apparel  and  other linens  to  give  them  body,  smoothness,  and  an improved appearance. Only cotton fabrics should be starched in the ship’s laundry. DO NOT starch synthetic  and  synthetic  blend  fabrics  or  work clothes. The amount of starch used should be the amount  indicated  on  the  formula. Starching  should  only  be  done  in  the automatic  mode;  however,  when  you  have  to  do it  manually,  follow  these  steps: 1.  Do  not  drain  the  sour/blue  bath.  Reduce water to a low level with the water at temperature indicated on the formula. Add the proper amount of  starch. 2.  Run  the  machine  for  4  minutes,  long enough  to  allow  the  starch  to  penetrate  the  shirts. 3.  Drain  the  starch  from  the  machine  while it is running to prevent the starch from settling on  the  load. WASHER   EXTRACTORS Washer  extractors  installed  aboard  ship  differ mainly in load capacity. The Naval Sea Systems Command   (NAVSEA)   publishes   the   N a v y Laundry  and  Dry-Cleaning  Equipment  Catalog (Tech Manual #S6152-B1-CAT-010). This catalog is  used  by  the  Navy  to  obtain  information  for identification,   selection,   and   procurement   of standard   naval   shipboard   laundry   and   dry- cleaning equipment. The washer extractors used by the Navy are listed in figure 5-13. This catalog includes several different types and sizes of washer extractors,  however,  the  Edro  (Dyna  Wash)  and the  Pellerin  Milnor  washers  are  the  ones  most widely  used  by  the  Navy. Washer extractors are basically made up into two  parts,  the  outer  shell  and  the  cylinder.  The shell  holds  the  water  and  cleaning  ingredients, while  the  cylinder  hold  the  clothes. The cylinder is perforated to allow water and suds in the bottom of the shell to enter and clean the  clothes  during  the  wash  cycle.  The  washer extractor then extracts the water from the cylinder by  using  centrifugal  force.  A  separate  extract motor spins the cylinder at a high speed to do this. OPERATION  OF  THE  WASHER EXTRACTOR  (EDRO  MODEL) The  washer  extractor  manufactured  by  the Edro   Corporation,   better   known   as   the   Dyna Wash,  is  procured  in  three  sizes—200-,  100-, or  60-pound  sizes.  The  100-pound  Dyna  Wash (including basic parts) is illustrated in figure 5-14. This washer extractor was designed to provide an easy  and  safe  method  of  washing  clothes, therefore,  training  personnel  to  operate  the machine  is  easy.  Since  the  washer  extractor  is automatic, the only thing the operator will have to  do  is  load,  add  supplies,  and  unload. WASHER   EXTRACTOR   CONTROLS The  Dyna  Wash  control  system  consists  of  two parts, the control panel and the programmer. The control  panel  is  illustrated  in  figure  5-15.  This panel may look slightly different on some models; however, the purpose of the basic controls on this panel is the same. The control switch energizes all electricity to the  control  panel  and  programmer.  This  control switch must be energized before you can use any of  the  basic  controls.  The  basic  controls  on the  control  panel  are  used  when  loading  and unloading   the   washer.   By   depressing   the   jog switch  simultaneously  with  the  reverse  or  forward switch,  the  washer  cylinder  will  rotate  in  that 5-19