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Bitumens
Bitumen is a term loosely applied to a number of plastic substances, varying in colour from dark brown to black, and with a characteristic odour, which occur naturally in many parts of the world, notably in Trinidad, Switzerland, and certain districts in the USA, and are also produced artificially.They include:
Asphalt.-Asphalt, or asphaltum, is a natural mixture of carbons, found in many different forms, some rock-like and some semi-plastic, of a dark-brown colour, melting at about 1000 C., giving off an acrid odour; it is combustible, insoluble in water and alcohol, slightly soluble in turpentine and easily so in coal-tar naphtha.
In its purified condition asphalt is largely used in the preparation of some paints and such varnishes as black japan, Brunswick black, Berlin black, etc.
For paint manufacture native asphalt is ground fine, with or without the addition of bitumen or other pitchy residues, and mixed with a suitable thinner and driers or, to the above, resin and colouring matter may be added.
The solvents used in asphalt paints are naphtha, benzol, petroleum, turpentine, carbon disulphide, and tetrachloride.
Asphalt in solution is used for impregnating felt and paper to be employed as damp-proofing materials, either as damp courses, flat against walls or under roofs, on floors, etc.
Such materials are commonly fixed in place by nails, but hot melted bitumen mastic may be used as a cement.
Pitch is a solid or thick viscid substance left after the dry distillation of carbons (coal, wood, petroleum) carried to a point before the residue becomes a hard solid, i.e. coke.
The longer the heat is applied, the darker, harder, and more brittle becomes the residual pitch.
It varies in colour from a light brown to a black.
Pitch is used in a crude form as a paint when melted;
it is also employed as an ingredient in the manufacture of black paints, varnishes, and japans.