﻿CLAYS 
  OF 
  NEW 
  YORK 
  767 
  

  

  SEWER 
  PIPE 
  

   Clays 
  used 
  

  

  The 
  qualities 
  of 
  clay 
  required 
  for 
  this 
  purpose 
  are 
  in 
  general 
  

   the 
  same 
  as 
  those 
  demanded 
  for 
  any 
  ware 
  with 
  a 
  vitrified 
  body. 
  

   They 
  should 
  therefore 
  be 
  sufficiently 
  plastic 
  to 
  permit 
  molding 
  

   without 
  cracking; 
  a 
  high 
  tensile 
  strength, 
  while 
  desirable, 
  is 
  not 
  

   absolutely 
  necessary. 
  Many 
  clays 
  used 
  in 
  the 
  manufacture 
  of 
  

   sewer 
  pipe 
  have 
  a 
  tensile 
  strength 
  as 
  high 
  as 
  125 
  or 
  even 
  150 
  

   pounds 
  a 
  square 
  inch, 
  while 
  on 
  the 
  other 
  hand 
  shales 
  are 
  used 
  

   whose 
  tensile 
  strength 
  when 
  ground 
  to 
  30 
  mesh 
  is 
  not 
  over 
  

   90 
  pounds 
  a 
  square 
  inch. 
  The 
  clay 
  should 
  bum 
  to 
  a 
  hard, 
  

   dense, 
  impervious 
  body; 
  the 
  amount 
  of 
  iron 
  in 
  such 
  clays 
  or 
  shales 
  

   is 
  usually 
  sufficient 
  to 
  color 
  it 
  a 
  red, 
  or 
  deep 
  red. 
  The 
  drying 
  

   should 
  be 
  rapid, 
  and 
  the 
  ware 
  should 
  not 
  warp 
  or 
  crack 
  in 
  drying. 
  

   Owing 
  to 
  the 
  thinness 
  of 
  the 
  body, 
  sewer 
  pipe 
  may 
  be 
  burned 
  more 
  

   rapidly 
  than 
  paving 
  brick. 
  

  

  An 
  excess 
  of 
  fluxing 
  impurities 
  may 
  render 
  a 
  clay 
  so 
  fusible 
  that 
  

   in 
  burning 
  it 
  softens 
  and 
  loses 
  shape. 
  It 
  is 
  a 
  very 
  common 
  prac- 
  

   tice 
  to 
  use 
  a 
  mixture 
  of 
  clays, 
  the 
  one 
  being 
  fusible 
  to 
  form 
  a 
  bond 
  

   in 
  burning, 
  the 
  other 
  more 
  refractory 
  to 
  preserve 
  the 
  shape 
  of 
  the 
  

   ware. 
  

  

  Sewer 
  pipe 
  are 
  usually 
  glazed 
  by 
  means 
  of 
  salt, 
  thrown 
  into 
  the 
  

   fireplaces 
  when 
  the 
  temperature 
  of 
  the 
  kiln 
  is 
  at 
  its 
  highest, 
  the 
  

   vapors, 
  passing 
  through 
  the 
  kiln 
  and 
  uniting 
  with 
  the 
  silica 
  and 
  

   the 
  alumina 
  of 
  the 
  clay, 
  forming 
  a 
  glaze 
  over 
  the 
  surface 
  of 
  the 
  

   ware. 
  The 
  following 
  is 
  the 
  reaction 
  which 
  occurs: 
  

  

  :NaCl+H20=H(JJ 
  + 
  Na 
  OH. 
  

  

  Na 
  OH+nSiO^NaO+nSiOsK^O. 
  

  

  Glazing 
  requires 
  one 
  to 
  two 
  hours; 
  some 
  manufacturers 
  add 
  

   manganese 
  to 
  the 
  salt 
  in 
  order 
  to 
  produce 
  a 
  glaze 
  of 
  the 
  proper 
  

   color. 
  An 
  excess 
  of 
  silica 
  in 
  the 
  clay 
  seems 
  to 
  be 
  detrimental 
  to 
  

   the 
  formation 
  of 
  a 
  good 
  glaze. 
  

  

  