“The subject of blistering of paint has from time to time engrossed the attention of practical men; but so far as we can follow it in the literature 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 been deluded by the known way of distilling water with the aid of sunshine without concentrating the rays of the sun, based upon the solubility of water in air, viz.:  Air holds more water in solution (or suspension) in a warmer than in a cooler degree of temperature; by means of a simple apparatus sun-heated air is guided over sun-heated