After  passing  through  the  pressure  gauge,  the ammonia   travels   through   a   flowmeter.   The flowmeter is located on the front of the machine, which  is  within  easy  reach  of  the  operator. With this meter, the operator is able to turn on or   off   the   ammonia   flow.   Additionally,   the operator is able to adjust the flow obtaining max- imum  development  with  a  minimum  amount  of ammonia.  Using  this  type  of  development  system, the operator is able to turn the ammonia supply on   only   when   developing,   thus   saving ammonia  during  warm-up  and  periods  of  idling or  nonuse. A  water  supply  is  used  to  aid  in  the  distri- bution  of  the  ammonia  vapor  within  the developing  tank.  Water  is  fed  into  the  evaporating drip  trays,  creating  additional  vapor,  which increases  the  ammonia’s  effectiveness.  This  water supply is controlled by a feed regulator (located on  the  front  of  the  machine).  Also  the  amount of water being supplied is visible through a tube above  the  feed  regulator.  Adjust  the  water  flow to  60  drops  per  minute,  and  ensure  that  a constant   dripping   of   water   is   reaching   the machine,  or  the  drip  trays  may  be  damaged. COOLING   AND   EXHAUST   SYSTEM.— Excessive  amounts  of  heat  or  ammonia  vapors should  NOT  reach  the  room  in  which  the  machine is  located  because  of  the  installed  exhaust  and cooling  system.  The  system  consists  of  twin blowers, driven by a motor that exhausts fumes and hot air from the machine enclosure through a  vent  to  the  outside  atmosphere.  Therefore,  a partial  vacuum  is  created  within  the  machine covers,  thereby  causing  air  to  flow  into  the machine rather than the counterflow that would otherwise  exist.  A  blower  time  switch  operates the  blower  motor  independently  of  the  rest of  the  machine  thereby  ensuring  the  removal of  vapors  and  hot  air  after  the  mercury-vapor lamp is turned off. The switch may be adjusted to  operate  for  any  given  length  of  time  up  to 30 minutes. MACHINE  OPERATION.—  A short warm- up  period  is  required  before  material  can  be fed  into  the  machine.  Always  follow  the manufacturer’s   instructions   during   machine operation.  When  starting  the  machine,  make  sure that the developer drain tube is inserted in the residue  bottle  (fig.  3-64).  Then,  fill  the  storage tank with ammonia. If bubbles are encountered in  the  feed  system  because  of  increased temperature  or  high  altitude,  dilute  the  ammonia with  cold  water.  Usually,  a  one-eighth  to  one- fourth  dilution  is  sufficient. After  the  ammonia  storage  tank  has  been filled,  turn  on  the  main  switch,  and  adjust  the ammonia feed to 50 to 60 drops per minute. At high speeds (30 ft per minute and above), the rate of drops per minute can be increased. On virtually all modern, large-size diazo machines, ammonia feed is automatically increased and decreased to correspond  with  variation  of  machine  speed. CAUTION During  machine  operation,  the  ammonia feed  regulator  should  NEVER  be  turned completely  off.  If  the  machine  is  left running  and  no  moisture  is  entering  the developer  section,  the  evaporation  tray  and heater rods are likely to be warped because of  excessive  heat. After a short warm-up period, the machine is ready for operation. The machine should be run for approximately 20 min or until the operating temperature  is  between  180°F  and  210°F.  Time and  temperature  may  vary;  therefore,  always follow the manufacturer’s instructions. Feed the material into the machine with the original on top, adjusting  the  speed  of  the  machine  so  that  a  clear print  is  obtained. Printing  speed  is  dependent  on  the  trans- lucency   of   the   original,   the   density   of   the opaque  image,  and  type  of  sensitized  material used. Running the machine at speeds that are too fast  will  result  in  a  background  on  the  print. Running  the  machine  too  slowly  will  cause  the image  to  be  weak  or  missing  from  the  print altogether.  The  only  positive  method  for obtaining  the  correct  speed  for  your  machine  is by  running  a  test  because  each  machine’s  light intensity changes with age. When   stopping   the   machine,   turn   the ammonia  flow  off,  then  feed  a  sheet  of  porous wrapping  paper,  16  in.  wide,  into  the  machine. Stop  the  machine  with  the  paper  in  position around  the  printing  cylinder  and  between  the sealing sleeve and the perforated tank. This will prevent  the  sleeve  from  sticking  to  the  perforated tank top and will also protect the belts from the heat  of  the  cylinder  while  it  is  cooling. 3-49