Dissolve  1  part  of  alum  and  3
parts  «)^f  sulphate  of  zinc  in  boiling
water,  pour  into  the  clear  mixture,
stir  the  whole  while  hot,  and  strain
into  a  mold  until  it  cools  and  jells.
The  mass  v/ill  now  be  thick  enough
to  remove  from  the  mold  and  dry
in  the  open  air  or  with  gentle  heat.
PAINTS   AND   PAINTING

Paint,  including  painting  and  the
care  of  paints,  is  an  important  sub-
ject. Both  the  inner  and  outer  walls
and  the  floors  of  houses  and  most
articles  of  furniture  are  painted.
Hence  a  knowledge  of  the  nature
and  properties  of  paint,  both  before
and  after  its  application,  enables  it
to  be  put  to  a  thousand  practical
uses  in  the  household.  The  uses  of
paint  are  twofold,  i.  e.,  to  protect
the    wood    and    other    materials    to


which  it  is  applied,  and  also  to  dec-
orate them.  The  ingredients  of  paint
are  of  two  sorts:  the  pigments  or
coloring  matter,  chosen  mostly  for
decoration;  and  the  vehicle  chosen  to
hold  the  coloring  matter  in  suspen-
sion, and  also,  when  desired,  to  fur-
nish the  requisite  protection.
Linseed  Oil  for  Paints. — The  best
vehicle  for  paints  used  to  protect
woodwork  and  other  surfaces  from
moisture  and  decay  is  linseed  oil.
This  is  one  of  the  so-called  drying
oils  which,  on  exposure  to  the  air,
absorb  oxygen  and  form  a  resinous
varnish  that  closes  the  pores  and  ex-
cludes the  agents  of  destruction  from
all  surfaces  to  which  it  is  applied.
Thus  it  holds  the  pigments  in  a  firm
waterproof   varnish.
