448 
A  NEW  PHOTOGRAPHIC  VARNISH,  ETC. 
pan.  If  a  little  be  now  dropped  on  to  a  cold  plate  or  piece  of 
toetal,  it  will  solidify  to  a  brittle  lump,  of  a  clear  rich  brown 
color,  showing  that  the  operation  has  succeeded.  All  that  now 
remains  is  to  add  sufficient  water  to  bring  the  mass  to  the  de- 
sired consistence.  The  water  must  be  boiling  when  added,  and 
in  very  small  quantities  at  a  time.  There  is  a  considerable  rush 
of  steam  as  the  first  portions  of  water  are  stirred  in,  and  care 
must  be  taken  in  using  the  paddle  to  stand  clear  of  the  hot  parti- 
cles projected  from  the  pan  j  but  after  a  few  additions  of  water 
all  this  subsides,  and  the  water  may  be  added  more  freely. 
The  finished  color  is  usually  sent  out,  either  as  a  stiff  paste- 
like extract^  in  which  condition  it  is  used  by  saddlers,  curriers, 
&c,  for  browning  certain  kinds  of  leather,  or  as  a  syrup  more  or 
less  thick.  In  this  last  form  it  is  used  for  coloring  vinegar,  spirits, 
gravies,  and  many  other  liquids,  and  is  well  known  in  the  drug 
trade  as  "  color  fuscus."  If  the  stiff  form  be  required,  about  a 
gallon  of  water  will  be  sufficient,  and  in  this  case  the  product 
should  be  got  out  while  hot,  and  put  into  stone-ware  jars,  pre- 
viously heated,  and  standing  on  a  piece  of  wood. 
Fifty  pounds  of  raw  sugar  should  yield  at  least  sixty  pounds 
of  the  stiff  color,  and  proportionately  more  of  the  thinner  kind, 
and  when  cold  should  dissolve  readily  in  water,  giving  a  clear 
brown  solution,  without  deposit  or  turpidity. 
The  causes  of  failure  in  the  manufacture  may  be  either  a  de- 
ficiency or  an  excess  of  heat. 
If  the  heat  used  be  insufficient,  some  of  the  sugar  remains  im- 
perfectly converted,  and  a  muddy  dirty-looking  product  is  the 
result.  On  the  other  hand,  if  the  heat  used  be  excessive  (strong 
heat  is  not  required  in  any  part  of  the  process),  the  mass  be- 
comes black,  granular,  and  insoluble  in  water,-— »in  fact,  burnt 
and  useless."^ Chem.  JSTews,  June  7,  1867. 
A  NEW  PHOTOGRAPHIC  TARNISH  FOR  PICTURES  AND 
NEGATIVES. 
By  Jk  GrasshoFf. 
In  order  to  give  albumenifced  prints  a  more  finished  appear- 
ance they  are  sometimes  coated  with  ordinary  negative  varnish, 
This  treatment  is  open  to  several  objections.    The  glossy  surface 
