WORKING  IN  ALUMINUN. 
555 
ceed  perfectly,  an  especial  acquaintance  with  the  subject  is 
needed. 
In  the  production  of  work  where  the  use  of  the  lathe  becomes 
necessary,  any  scratching  or  tearing  of  the  metal  by  the  tool  is 
avoided  by  covering  the  surface  to  which  the  tool  is  applied  with 
a  varnish  composed  of  stearic  acid  and  essence  of  turpentine. 
When  aluminum  is  soiled  by  greasy  matters,  it  can  be  cleaned 
by  benzole;  if  it  be  soiled  by  dust  only,  india-rubber,  or  very 
weak  soap  and  water  may  be  used. 
The  pieces  of  aluminum  intended  to  be  soldered  must  be  pre- 
pared in  the  same  manner  as  objects  are  treated  for  soldering 
with  tin,  viz.,  by  a  tinning  ;  "  but  it  must  be  remembered  that 
it  is  indispensable  that  this  tinning  must  take  place  with  the 
solder  itself.  The  pieces  to  be  soldered,  thus  tinned  beforehand, 
are  afterwards  joined  together,  and  exposed  to  the  flame,  either 
of  a  gas  blowpipe,  or  any  of  the  ordinary  sources  of  heat  used 
in  such  cases.  In  order  to  unite  the  solderings,  small  tools  of 
aluminum  are  used.  These  tools  are  used  as  little  soldering 
instruments,  and  they  facilitate  at  the  same  time  the  fusion  of 
the  solder,  and  its  adhesion  to  the  previously  prepared  aluminum. 
The  use  of  tools  of  copper  or  brass  used  when  soldering  gold 
and  silver,  must  be  strictly  avoided,  as  they  would  form  colored 
alloys  with  the  aluminum  and  the  solder.  It  is  of  the  greatest 
importance  never  to  use  any  flux  to  cause  the  solder  to  melt,  as 
all  those  at  present  known  attack  aluminum,  and  prevent  the 
adhesion  of  the  pieces  to  be  soldered.  The  use  of  the  little 
tools  of  aluminum  is  an  art  which  the  workmen  must  acquire  by 
practice  ;  in  fact,  at  the  moment  of  fusion  the  solderings  must 
have  the  friction  applied,  as  they  melt  suddenly  in  a  complete 
manner.  In  soldering  aluminum,  it  is  well  to  have  both  hands 
free,  and  to  use  only  the  foot  for  the  blowing  apparatus. 
Solders  of  different  compositions  and  degrees  of  fusibility 
have  been  employed  in  soldering  aluminum.  The  following  are 
those  which  have  been  generally  used,  ranged  according  to  their 
order  of  fusibility : 
I. 
II. 
III. 
IV. 
V, 
Zinc 
.  80 
85 
88 
90 
94 
Copper  . 
.  8 
6 
5 
4 
2 
Aluminum  . 
.  12 
9 
7 
6 
4 
