ON  A  NEW  PROCESS  FOR  ELECTRO-GILDING. 
357 
fire-gilding,  several  hours  are  required.  When  the  liquid  is  ex- 
hausted of  its  gold,  fresh  oxide  is  added,  by  which  a  further 
precipitation  of  oxide  of  iron  is  produced.'  The  gilding  obtained 
by  this  process  admits  of  being  burnished,  and  of  undergoing 
all  the  operations  employed  to  produce  mat  or  dead  gold. 
One  of  the  most  difficult  problems  to  solve  in  this  branch  of 
manufacture  is  the  production  of  dead  surfaces.  Although  we 
know  the  nature  and  manipulation  of  the  process,  it  is  only  the 
Parisian  workmen  who  perfectly  succeed  in  this  field ;  hence 
it  is  that  these  operations  are  always  conducted  by  French 
workmen,  as  well  in  native  as  in  foreign  establishments  of  im- 
portance. 
The  production  of  dead  gold  in  the  ordinary  way  is  always 
accompanied  by  loss  of  metal,  inasmuch  as  it  necessitates  a  sys- 
tem of  corrosion  of  the  surface  by  chlorine.  By  Briant's  process 
a  matted  surface  can  be  obtained  by  galvanic  agency  not  infe- 
rior to  the  best  of  Paris,  while  it  does  not  require  any  of  the 
subsequent  operations  required  in  fire-gilding.  The  mat  appear- 
ance is  spontaneously  produced  as  soon  as  the  coating  of  gold 
has  acquired  a  certain  thickness ;  it  is  most  beautiful  when  the 
operation  is  carried  on  in  the  cold.  By  a  very  simple  artifice 
a  more  or  less  reddish  tint  on  the  one  hand,  or  a  whitish  one  on 
the  other,  is  produced ;  it  is  merely  requisite  to  dilute  the  bath 
with  more  or  less  water. 
When  the  objects  to  be  gilded  are  polished  and  brilliant,  the 
electro-gilding  will  also  be  brilliant,  and  it  requires  a  longer 
time,  and  a  thicker  coating  of  gold  to  produce  a  deadened  sur- 
face. It  is  therefore  important  to  communicate,  in  the  first  in- 
stance, a  deadened  surface  to  the  objects  by  the  process  em- 
ployed in  fire-gilding ;  or,  more  economically,  by  covering  them 
at  once  with  a  thin  pellicle  of  copper  by  the  electric  agency, 
which,  as  is  well  known,  produces  a  beautiful  matted  surface. 
When  any  part  of  the  object  is  to  be  protected  from  the  action 
of  the  gilding  process,  the  choice  of  the  substances  to  be  used 
in  "  stopping  out"  these  parts  is  of  importance,  for  it  must  be 
remembered  that  the  bath  is  alkaline  ;  for  this  purpose  plaster 
impregnated  with  an  alcoholic  solution  of  lac  is  recommended. 
— Chem.  Cfaz,9  Aprillft,  from  Bulletin  de  la  Societe  oV  Encour- 
agement. 
