54  Japanese  Lac.  {^SS^SSt 
4  In  the  following  year  Prof.  J.  J.  Rein  made  a  thorough  study  of  the 
method  of  collecting  and  applying  the  lac. 
The  pure  lac  is  a  natural  product  of  Rhus  vcrnicifera,  a  small 
tree  about  15  feet  high,  growing  wild  in  China  and  Japan,  where  it 
is  also  cultivated  in  many  parts  of  the  country.  The  largest  yield  is 
from  trees  about  fifteen  years  old,  but  the  age  of  the  tree  when  the 
lac  is  collected  varies  in  different  localities,  in  some  places  at  from 
five  to  six  years  when  the  stem  is  the  size  of  a  man's  arm,  and  in 
other  localities  at  from  nine  to  ten  years  old.  The  time  of  collect- 
ing is  from  April  to  the  1st  of  November. 
The  lac  is  obtained  by  making  horizontal  incisions  in  the  bark 
with  a  hook- shaped  instrument  and  alternating  from  side  to  side  of 
the  tree.  The  sap  is  removed  from  the  incisions  with  a  pointed 
spatula.  These  operations  are  repeated  at  intervals  of  about  four 
days  until  the  tree  is  literally  covered  with  grooves.  The  lac  is  in 
the  form  of  a  grayish-white  emulsion,  which,  on  exposure  to  air, 
changes  to  brown  and  finally  to  black.  The  raw  lac  is  strained  to 
remove  pieces  of  bark,  and  then  mixed  until  uniform,  when  it  is 
ready  for  use,  and  is  known  as  "  Ki-Urushi."  A  second  grade 
known  as  "  Seshime-Urushi  "  is  obtained  at  the  close  of  the  season 
by  cutting  and  binding  the  branches  into  bundles  and  macerating 
these  with  the  trunk  in  warm  water,  when  more  of  the  sap  exudes 
and  is  removed  from  the  surface  of  the  water. 
The  beautiful  black  color  is  produced  by  "  Laccasse,"  a  soluble 
oxidizing  enzyme,  acting  on  the  resins  in  the  presence  of  moisture. 
The  best  results  are  obtained  by  allowing  the  lac  to  harden  in  a 
moist  atmosphere.  Therefore,  the  articles  coated  with  the  lac  are 
placed  in  a  room  and  wet  clothes  hung  on  the  walls  or  about  the 
lacquered  articles.  A  temperature  of  from  200  to  300  is  best  for  the 
action  of  the  enzyme.  If  the  lac  is  allowed  to  harden  in  a  dry 
atmosphere  it  has  a  dull  appearance,  varying  in  shade  from  brown 
to  black. 
The  most  important  chemical  investigations  of  this  lac  were  made 
by  two  Japanese  chemists.1  Yoshida  reports  that  the  lac  consisted 
of  a  non-volatile  resinous  acid,  which  he  calls  urushic  acid,  a  volatile 
poison,  gum,  identical  with  gum  arabic,  diastatic  matter  and  water. 
1  H.  Yoshida,  Jour.  Chem.  Soc,  1883,  p.  472.  O.  Korschelt  aud  H.  Yoshida, 
Transact.  As.  Soc,  Japan,  XIT,  p.  182. 
