Asphalts.

Progress, Volume IV, Issue 5, 1 March 1909, Page 173

Asphalts.

Asphalts vary from semi-liquid to very hard and brittle, and from 100 per cent, pure to half or more earth, sand, or refuse. Bitumen or pure bitumen also varies, from the hard and brittle to softer and pliable. Different parts of the world turn out very different products in these hydrocarbons according to the environment.

Trinidad has hard asphalt, Switzerland also has very hard asphalt, and three or four States of U.S. of America produce a pure and pliable bitumen peculiar to that country. If hard asphalt is used for portable roofings and damp-courses, the asphalt itself may be fairly good, but it must be softened out to make it pliable, and one of the easiest and commonest ways to do this is to mix an animal fat residue with

it. In other cases a soft and semi-liquid material such as coal or Stockholm tar is used, but this of course must be thickened, and a good vegetable matter is the thing to thicken it up with.

In the process of refining asphalts and bitumens, many different consistencies of residue are the result, and the pure hard asphalt is one of these residues. If the

inferior "Oid" or "Ite" is made by using this hard residue mixed with the animal fat its "class name," asphalt, gives it a certain appearance and sound of durability which is very misleading. The pure bitumen which is in a pliable state when cold should make a first-class and very durable portable roofing or damp-course, and command entire confidence by the profession. It is therefore very necessary indeed for architects to see that a reliable material is specified, and actually used when their

specification is being followed, and builders should be warned against the possibility of some materials proving unsatisfactory in a year or two, or even less, when doing good work. An instance occurred only recently when one of our leading builders found the "portable material" was actually useless before he handed over the finished job. These remarks apply with equal force to various flat roof materials now being offered. — Building, Sydney.