﻿812 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  source. 
  When 
  complicated 
  forms 
  are 
  placed 
  in 
  the 
  sagger 
  the 
  over- 
  

   hanging 
  or 
  greatly 
  projecting 
  portions 
  are 
  supported 
  by 
  pieces 
  

   which 
  have 
  the 
  same 
  composition 
  as 
  the 
  ware 
  itself^ 
  so 
  that 
  in 
  

   burning 
  the 
  shrinkage 
  of 
  both 
  will 
  be 
  the 
  same. 
  

  

  The 
  proper 
  placing 
  of 
  the 
  ware 
  in 
  the 
  kiln 
  as 
  well 
  as 
  in 
  the 
  

   saggers 
  is 
  a 
  matter 
  of 
  great 
  importance. 
  

  

  The 
  condition 
  of 
  the 
  fires 
  in 
  the 
  burning 
  of 
  porcelain 
  or 
  earthen- 
  

   ware 
  has 
  to 
  be 
  taken 
  into 
  consideration. 
  In 
  the 
  burning 
  of 
  spar 
  

   china 
  from 
  redness 
  up 
  to 
  the 
  point 
  of 
  vitrification, 
  it 
  is 
  desirable 
  to 
  

   have 
  the 
  fire 
  reducing 
  in 
  its 
  action, 
  while 
  above 
  that 
  point 
  it 
  should 
  

   be 
  neutral 
  or 
  weakly 
  oxidizing. 
  In 
  using 
  coal 
  which 
  contains 
  

   pyrite, 
  if 
  the 
  fire 
  is 
  oxidizing, 
  sulfuric 
  acid 
  is 
  set 
  free; 
  and 
  this 
  

   tends 
  to 
  unite 
  with 
  any 
  lime 
  carbonate 
  or 
  -alkalis 
  which 
  the 
  glaze 
  

   may 
  contain, 
  the 
  lower 
  the 
  temperature 
  of 
  the 
  kiln 
  the 
  more 
  rapid 
  

   this 
  union, 
  for 
  the 
  lime 
  and 
  alkalis 
  will 
  unite 
  with 
  the 
  sulfuric 
  

   acid, 
  as 
  long 
  as 
  they 
  have 
  not 
  entered 
  in 
  combination 
  with 
  the 
  silica 
  

   of 
  the 
  glaze. 
  When 
  the 
  glaze 
  has 
  once 
  melted, 
  the 
  danger 
  that 
  this 
  

   will 
  take 
  place 
  is 
  far 
  less. 
  If 
  the 
  gases 
  are 
  reducing, 
  any 
  sulfate 
  

   salts 
  formed 
  are 
  broken 
  up 
  and 
  sulfurous 
  acid 
  gas 
  escapes. 
  If 
  the 
  

   glaze 
  particles 
  have 
  not 
  yet 
  been 
  thoroughly 
  fused 
  the 
  gas 
  just 
  

   mentioned 
  escapes 
  without 
  causing 
  any 
  trouble; 
  but, 
  if 
  the 
  fusion 
  

   has 
  already 
  occurred, 
  blistering 
  or 
  scaling 
  of 
  the 
  glazed 
  surface 
  re- 
  

   sults. 
  

  

  Both 
  the 
  body 
  and 
  the 
  glaze 
  may 
  sometimes 
  have 
  a 
  small 
  amount 
  

   of 
  gypsum, 
  which 
  may 
  come 
  from 
  an 
  Alsing 
  cylinder, 
  if 
  such 
  a 
  

   machine 
  is 
  used 
  for 
  grinding 
  the 
  clay. 
  The 
  reducing 
  action 
  of 
  the 
  

   fire 
  must, 
  however, 
  not 
  be 
  too 
  strong, 
  otherwise 
  any 
  organic 
  matter 
  

   which 
  the 
  clay 
  contains 
  will 
  not 
  burn 
  off 
  at 
  the 
  proper 
  time, 
  and 
  

   will 
  subsequently 
  be 
  liable 
  to 
  cause 
  bursting 
  in 
  the 
  ware 
  during 
  

   burning. 
  A 
  reducing 
  fire 
  tends 
  to 
  insure 
  a 
  whiter 
  color 
  in 
  the 
  ware 
  

   by 
  reducing 
  any 
  ferric 
  combination 
  of 
  iron, 
  thus 
  carrying 
  the 
  color 
  

   from 
  reddish 
  over 
  into 
  whitish 
  gray, 
  or 
  the 
  pale 
  green 
  of 
  complex 
  

   ferrous 
  silicates. 
  The 
  latter 
  are 
  hardly 
  noticeable 
  so 
  that 
  the 
  whole 
  

   body 
  appears 
  white. 
  It 
  sometimes 
  happens 
  that 
  during 
  the 
  slow 
  

  

  