pertaining to the building trade, its cause has never been
clearly laid down, and hence it is a detail enshrouded in mystery."

W.S. dwells mostly, in his following explanations on blistering
paints, on steam raised in damp wood. Also an English painter,
according to the _Painters' Journal_, lately reiterates the same
theory, and gives sundry reasons how water will get into wood through
paint, but is oblivious that the channels which lead water into wood
are open to let it out again. He lays great stress on boiled oil
holding water in suspense to cause blistering, which is merely a
conjecture. Water boils at 212 deg. F. and linseed oil at 600 deg. F.,
consequently no water can possibly remain after boiling, and a drop of
water put into boiling oil would cause an explosion too dangerous to
be encountered.

It will be shown herewith that boiled oil, though in general use, is
unfit for durable painting, that it is the cause of most of the
troubles painters have to contend with, and that raw linseed oil
seasoned by age is the only source to bind pigments for durable
painting; but how to procure it is another trouble to overcome, as all
our American raw linseed oil has been heated by the manufacturers, to
qualify it for quick drying and an early market, thereby impairing its
quality. After linseed oil has been boiled, it becomes a poor varnish;
it remains soft and pliable when used in paint, giving way to air
pressure from the wood in hot weather, forming blisters. Turpentine
causes no blistering; it evaporates upon being exposed, and leaves the
paint in a porous condition for the gas in the wood to escape; but all
painters agree that blistering is caused by gas, and on investigation
we find two main sources from which gas is generated to blister
paint--one from the wood, the other from the ingredients of the paint.
The first named source of gas is started in hot weather by expansion
of air confined in painted wood, which presses against the paint and
raises blisters when the paint is too soft to resist. Tough,
well-cemented paint resists the pressure and keeps the air back. These
blisters mostly subside as soon as the air cools and returns to the
pores, but subsequently peel off.

W.S. and others assert that damp in painted wood turns into steam when
exposed to sun heat, forming blisters, which cannot be possible when
we know that water does not take a gaseous form (steam) at less than
212 deg. F. They have very likely b