﻿680 
  NEW 
  YOKK 
  STATE 
  MUSEUM 
  

  

  escence 
  is 
  " 
  saltpeter 
  ^\ 
  and 
  when 
  it 
  occurs 
  in 
  burning 
  the 
  manu- 
  

   facturer 
  at 
  times 
  erroneously 
  ascribes 
  it 
  to 
  water-smoking. 
  

  

  The 
  efflorescence 
  is 
  usually 
  due 
  to 
  the 
  presence 
  of 
  soluble 
  salts, 
  

   specially 
  sulfates, 
  which 
  are 
  formed 
  either 
  in 
  the 
  clay 
  or 
  during 
  

   some 
  stage 
  of 
  the 
  manufacture. 
  Any 
  moisture 
  present 
  in 
  the 
  clay 
  

   or 
  product 
  dissolves 
  these 
  compounds 
  and 
  on 
  evaporation 
  carries 
  

   them 
  to 
  the 
  surface 
  of 
  the 
  ware. 
  

  

  The 
  subject 
  has 
  been 
  discussed 
  in 
  some 
  detail 
  in 
  the 
  Brich- 
  

   huilder, 
  from 
  wdiich 
  the 
  following 
  points 
  are 
  taken. 
  -^ 
  

  

  1 
  Formation 
  of 
  efflorescence 
  in 
  the 
  clay 
  beds, 
  etc. 
  Most 
  clays 
  con- 
  

   tain 
  mineral 
  salts 
  in 
  greater 
  or 
  less 
  quantities, 
  w^hich 
  chemical 
  

   analysis 
  has 
  shown 
  to 
  be 
  sulfates 
  of 
  lime 
  and 
  magnesia, 
  less 
  fre- 
  

   quently 
  of 
  iron 
  and 
  alkalis. 
  The 
  formation 
  of 
  these 
  sulfates 
  is 
  

   generally 
  due 
  to 
  the 
  decomposition 
  of 
  iron 
  pyrite 
  contained 
  in 
  the 
  

   clay, 
  and 
  it 
  will 
  be 
  seen 
  that 
  the 
  more 
  thoroughly 
  this 
  material 
  is 
  

   distributed 
  throughout 
  the 
  clay 
  the 
  more 
  easily 
  it 
  will 
  be 
  subjected 
  

   to 
  complete 
  deco'mposition, 
  and 
  the 
  greater 
  amount 
  of 
  soluble 
  sul- 
  

   fates 
  will 
  be 
  foraied. 
  All 
  clays 
  do 
  not 
  contain 
  iron 
  pyrites. 
  In 
  any 
  

   one 
  clay 
  bank 
  the 
  pyrites 
  may 
  be 
  more 
  abundant 
  in 
  some 
  layers 
  than 
  

   in 
  others. 
  It 
  may 
  be 
  present 
  in 
  equal 
  quantities 
  in 
  all 
  layers, 
  but 
  

   its 
  decomposition 
  may 
  have 
  proceeded 
  to 
  a 
  greater 
  extent 
  in 
  those 
  

   beds 
  which 
  are 
  the 
  most 
  weathered. 
  This 
  fact 
  has 
  been 
  brought 
  out 
  

   by 
  Dr 
  Gerlach's 
  observations. 
  One^ 
  of 
  these 
  was 
  that 
  clay 
  which 
  

   had 
  been 
  allowed 
  to 
  lie 
  for 
  months 
  in 
  the 
  open 
  air 
  left 
  behind 
  on 
  

   the 
  ground 
  where 
  it 
  had 
  been 
  large 
  quantities 
  of 
  beauitiful 
  gypsum 
  

   crystals; 
  but 
  the 
  omission 
  of 
  the 
  intermediate 
  operation 
  of 
  allowing 
  

   the 
  clay 
  to 
  weather 
  after 
  it 
  has 
  been 
  dug 
  will 
  not 
  necessarily 
  pre- 
  

   vent 
  the 
  fomiation 
  of 
  these 
  soluble 
  sulfates, 
  for 
  the 
  same 
  decompo- 
  

   sition 
  of 
  the 
  pyrites 
  may 
  occur 
  if 
  the 
  green 
  bricks 
  are 
  allowed 
  to 
  

   stand 
  a 
  long 
  time 
  in 
  the 
  drying-room, 
  in 
  the 
  presence 
  of 
  moisture. 
  

   The 
  prevention 
  therefore 
  would 
  seem 
  to 
  be 
  in 
  the 
  ordinary 
  molding 
  

   of 
  the 
  clay 
  and 
  the 
  drying 
  and 
  burning 
  of 
  the 
  bricks 
  as 
  quickly 
  as 
  

   possible. 
  Tliis 
  oxidation 
  and 
  decomposition 
  of 
  iron 
  pyrites 
  is 
  there- 
  

  

  1 
  0. 
  Gerlach, 
  Brickbuilder. 
  1898. 
  p. 
  59. 
  et 
  seq. 
  

  

  