﻿854 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  TESTIE'G 
  OF 
  CLAY 
  WAKES 
  

  

  Tlie 
  tests 
  applied 
  to 
  determine 
  the 
  qualities 
  of 
  a 
  clay 
  product 
  

   depend 
  on 
  the 
  use 
  to 
  which 
  it 
  is 
  to 
  be 
  put. 
  Some 
  wares 
  such 
  as 
  

   paving 
  bricks 
  are 
  subjected 
  to 
  sudden 
  shocks 
  and 
  abrasion, 
  others, 
  

   which 
  are 
  placed 
  in 
  exposed 
  positions, 
  must 
  withstand 
  the 
  influ- 
  

   ence 
  of 
  weather, 
  still 
  others 
  must 
  resist 
  sudden 
  changes 
  of 
  tem- 
  

   perature, 
  etc. 
  

  

  Porosity 
  or 
  permeability 
  

  

  The 
  denser 
  a 
  building 
  brick 
  the 
  better 
  it 
  will 
  be 
  able 
  to 
  with- 
  

   stand 
  weathering 
  influences. 
  Soft 
  mud 
  bricks 
  are 
  perhaps 
  an 
  ex- 
  

   ception 
  to 
  this 
  rule, 
  for 
  they 
  may 
  often 
  exhibit 
  16^ 
  or 
  20^ 
  porosity 
  

   and 
  still 
  resist 
  frost 
  action. 
  The 
  porosity 
  of 
  course 
  depends 
  on 
  

   the 
  density, 
  and 
  is 
  determined 
  by 
  the 
  increase 
  of 
  weight 
  which 
  a 
  

   brick 
  shows 
  when 
  immersed 
  in 
  water. 
  It 
  may 
  also 
  be 
  of 
  interest 
  

   or 
  importance 
  at 
  times 
  to 
  determine 
  the 
  porosity 
  of 
  the 
  different 
  

   parts 
  of 
  a 
  brick, 
  in 
  which 
  case 
  the 
  brick 
  is 
  broken 
  up 
  and 
  frag- 
  

   ments 
  taken 
  from 
  the 
  center. 
  

  

  The 
  absorption 
  of 
  common 
  building 
  brick 
  may 
  be 
  as 
  much 
  as 
  

   20^ 
  of 
  their 
  weight, 
  while 
  in 
  the 
  case 
  of 
  hard 
  brick 
  it 
  should 
  not 
  

   exceed 
  6^ 
  ; 
  in 
  paving 
  bricks 
  and 
  bricks 
  for 
  sewers 
  not 
  over 
  2^, 
  and 
  

   in 
  sewer 
  pipe 
  and 
  canal 
  brick 
  it 
  should 
  never 
  get 
  above 
  1^. 
  

  

  According 
  to 
  Dtimmler 
  (Ziegel 
  Fahrikation, 
  p. 
  71) 
  it 
  is 
  import- 
  

   ant 
  in 
  the 
  case 
  of 
  vitrified 
  roofing 
  tile 
  and 
  sewer 
  pipe 
  to 
  determine 
  

   not 
  only 
  the 
  porosity 
  but 
  also 
  the 
  permeability. 
  With 
  roofing 
  tile, 
  

   which 
  simply 
  serve 
  to 
  drain 
  off 
  water, 
  this 
  is 
  done 
  by 
  heating 
  the 
  

   tile 
  first 
  to 
  100° 
  C, 
  then 
  placing 
  on 
  it 
  a 
  tube 
  whose 
  cross-section 
  is 
  

   10 
  square 
  centimeters, 
  and 
  whose 
  hight 
  is 
  20 
  cm. 
  This 
  is 
  

   fastened 
  to 
  the 
  tile 
  by 
  means 
  of 
  wax, 
  and 
  then 
  filled 
  with 
  lOcc 
  

   of 
  water. 
  The 
  time 
  is 
  then 
  noted 
  which 
  this 
  water 
  takes 
  to 
  soak 
  

   in, 
  and 
  additional 
  quantities 
  of 
  10 
  to 
  15 
  cc 
  are 
  added 
  at 
  a 
  time 
  

   till 
  drops 
  begin 
  to 
  appear 
  on 
  the 
  under 
  side 
  of 
  the 
  tile. 
  Koofing 
  

  

  