﻿CLAYS 
  OF 
  ^'EW 
  YOEK 
  549 
  

  

  to 
  quartz 
  sand, 
  both 
  artificial 
  and 
  natural 
  flint, 
  which 
  is 
  the 
  

   amorphous 
  form 
  of 
  quartz, 
  often 
  furnishes 
  a 
  grog 
  of 
  splendid 
  

   purity. 
  Quartz 
  when 
  exposed 
  to 
  high 
  temperature 
  gradually 
  passes 
  

   from 
  a 
  crystalline 
  to 
  an 
  amorphous 
  condition 
  and 
  in 
  so 
  doing 
  ex- 
  

   pands. 
  

  

  The 
  more 
  nearly 
  round 
  the 
  gTains 
  of 
  sand, 
  the 
  greater 
  will 
  be 
  

   the 
  interstitial 
  space. 
  In 
  the 
  case 
  of 
  quartz 
  sand 
  this 
  amounts 
  to 
  

   35^ 
  or 
  40^. 
  In 
  fine 
  mica 
  sand 
  (glazing 
  sand, 
  for 
  instance) 
  it 
  may 
  

   reach 
  50;^; 
  and 
  the 
  more 
  mica 
  that 
  is 
  mixed 
  with 
  quartz 
  sand 
  the 
  

   greater 
  is 
  the 
  amount 
  of 
  interstitial 
  space, 
  and 
  the 
  lighter 
  the 
  

   weight. 
  

  

  Dummler 
  gives 
  the 
  following 
  figures 
  for 
  one 
  liter 
  of 
  sand, 
  the 
  

   material 
  in 
  each 
  case 
  being 
  compacted 
  by 
  shaking 
  and 
  jarring. 
  

  

  One 
  liter 
  common 
  moist 
  sand, 
  1.61 
  kilogTams. 
  

  

  One 
  liter 
  fine 
  quartz 
  sand, 
  1.57 
  kg.; 
  porosity, 
  35^ 
  to 
  40^. 
  

  

  One 
  liter 
  fine 
  chamotte 
  flour 
  from 
  hard 
  burned 
  material, 
  1.43 
  kg. 
  ; 
  

   porosity, 
  45^. 
  

  

  One 
  liter 
  mica 
  sand 
  (glazing 
  sand), 
  1.30 
  kg.; 
  porosity, 
  about 
  

   50^. 
  

  

  One 
  liter 
  of 
  the 
  finest 
  ground 
  quartz 
  or 
  feldspar 
  flour, 
  1.16 
  kg.; 
  

   porosity, 
  about 
  56;^. 
  

  

  Chamotte. 
  This 
  is 
  the 
  term 
  applied 
  to 
  burned 
  clay. 
  It 
  pos- 
  

   sesses 
  all 
  the 
  advantages 
  of 
  quartz 
  as 
  a 
  diluent 
  of 
  the 
  shrinkage, 
  

   but 
  has 
  the 
  advantage 
  over 
  it 
  that 
  it 
  does 
  not 
  afiect 
  the 
  fusibility 
  of 
  

   the 
  clay, 
  or 
  swell 
  with 
  an 
  increase 
  of 
  temperature. 
  Hence, 
  it 
  does 
  

   not 
  tend 
  to 
  loosen 
  the 
  structure 
  of 
  the 
  finished 
  product. 
  The 
  clay 
  

   used 
  for 
  this 
  purpose 
  must 
  be 
  burned 
  to 
  such 
  an 
  extent 
  that 
  it 
  will 
  

   not 
  shrink 
  on 
  being 
  farther 
  subjected 
  to 
  heat. 
  The 
  degree 
  to 
  which 
  

   this 
  burned 
  clay 
  is 
  ground 
  depends 
  on 
  the 
  use 
  to 
  which 
  it 
  is 
  put 
  ; 
  for, 
  

   to 
  produce 
  a 
  porous 
  body, 
  it 
  is 
  not 
  ground 
  as 
  fine 
  as 
  it 
  would 
  be 
  if 
  a 
  

   dense 
  one 
  were 
  to 
  be 
  made. 
  The 
  burned 
  clay 
  used 
  for 
  this 
  purpose 
  

   can 
  either 
  be 
  ground 
  up 
  bits 
  of 
  broken 
  ware, 
  or 
  can 
  be 
  clay 
  

   specially 
  burned 
  for 
  this 
  use. 
  Through 
  the 
  hard 
  burning 
  of 
  clay, 
  

   or 
  the 
  repeated 
  burning 
  of 
  some 
  wares, 
  as 
  in 
  the 
  case 
  of 
  retorts, 
  the 
  

   1 
  Deutscher 
  ziegler-kalender, 
  1898, 
  p. 
  81. 
  

  

  