﻿762 
  NEW 
  YORK 
  STATE 
  MTSEUM 
  

  

  object 
  are 
  trimmed 
  off 
  bj 
  means 
  of 
  a 
  knife. 
  Large 
  objects 
  such 
  

   as 
  a 
  statue 
  or 
  column 
  have 
  to 
  be 
  molded 
  in 
  several 
  pieces, 
  a 
  sepa- 
  

   rate 
  mold 
  being 
  required 
  for 
  each. 
  Indeed 
  extreme 
  care 
  has 
  to 
  

   be 
  exercised 
  not 
  to 
  make 
  single 
  pieces 
  which 
  are 
  too 
  large 
  or 
  too 
  

   complicated, 
  otherwise 
  they 
  would 
  warp 
  and 
  crack 
  in 
  drying 
  and 
  

   burning. 
  

  

  Drying 
  of 
  the 
  wares 
  needs 
  to 
  proceed 
  with 
  great 
  slowness, 
  and 
  

   in 
  the 
  case 
  of 
  larger 
  pieces 
  has 
  even 
  to 
  be 
  retarded 
  by 
  keeping 
  

   them 
  covered 
  with 
  a 
  damp 
  cloth. 
  The 
  drying 
  process 
  is 
  carried 
  

   on 
  in 
  warm 
  rooms; 
  where, 
  in 
  some 
  terra 
  cotta 
  factories, 
  coils 
  of 
  

   steam 
  pipe 
  are 
  laid 
  under 
  the 
  floor. 
  The 
  shrinkage 
  of 
  terra 
  cotta 
  

   in 
  burning 
  and 
  drying 
  is 
  commonly 
  about 
  iV- 
  

  

  Much 
  terra 
  cotta 
  is 
  covered 
  either 
  with 
  a 
  soft 
  dull 
  enamel, 
  or 
  

   glaze. 
  This 
  is 
  commonly 
  applied 
  by 
  dipping 
  the 
  green 
  ware 
  into 
  

   the 
  glazing 
  liquid, 
  or 
  it 
  is 
  put 
  on 
  by 
  spraying, 
  (pi. 
  77.) 
  

  

  In 
  the 
  burning 
  of 
  the 
  ware, 
  simple 
  forms. 
  can 
  be 
  piled 
  on 
  one 
  

   another 
  in 
  the 
  kiln, 
  but 
  larger 
  and 
  more 
  complicated 
  pieces 
  have 
  

   to 
  be 
  set 
  in 
  between 
  slabs 
  of 
  firebrick, 
  to 
  shield 
  them 
  from 
  any 
  

   pressure 
  during 
  the 
  burning. 
  Both 
  coal 
  and 
  oil 
  are 
  used 
  as 
  fuel, 
  

   the 
  latter 
  having 
  met 
  with 
  success 
  at 
  the 
  works 
  of 
  the 
  ISTew 
  York 
  

   architectural 
  terra 
  cotta 
  co. 
  

  

  The 
  color 
  of 
  terra 
  cotta 
  is 
  either 
  that 
  of 
  the 
  body 
  or 
  is 
  imparted 
  

   by 
  a 
  thin 
  coating 
  of 
  slip. 
  The 
  slipping 
  of 
  terra 
  cotta 
  is 
  extensively 
  

   practised, 
  the 
  advantages 
  being 
  that 
  it 
  makes 
  the 
  color 
  of 
  the 
  clay 
  

   when 
  burned 
  immaterial, 
  since 
  the 
  color 
  of 
  the 
  object 
  is 
  given 
  by 
  

   the 
  slip 
  coating. 
  

  

  According 
  to 
  the 
  composition 
  of 
  the 
  slip, 
  the 
  surface 
  is 
  dull^ 
  

   enameled 
  or 
  glazed. 
  The 
  composition 
  of 
  the 
  coating 
  must 
  be 
  such 
  

   of 
  course 
  that 
  the 
  coefficient 
  of 
  expansion 
  of 
  the 
  body 
  and 
  of 
  the 
  

   coating 
  is 
  the 
  same, 
  otherwise 
  a 
  crazing 
  of 
  the 
  surface 
  is 
  sure 
  to 
  

   ensue. 
  

  

  The 
  temperature 
  reached 
  in 
  the 
  burning 
  of 
  terra 
  cotta 
  depends 
  

   on 
  the 
  refractoriness 
  of 
  the 
  clay. 
  For 
  calcareous 
  clays 
  the 
  tem- 
  

   perature 
  seldom 
  exceeds 
  2000° 
  F., 
  but 
  when 
  semi-fire 
  clays 
  are 
  

  

  