Maximum water and Weather resistance is obtained by using a paint containing gilsonite and the gas-proofed tung or oiticica (or mixtures of the two) oil without the addition of any other drying oil, but it is found that while this combination is commercially usable, it is difficult to brush, and it is preferred to add a viscosity reducing drying oil. For this purpose it is found that perilla oil is particularly satisfactory. Other drying oils such as linseed, soya bean, sunflower seed, hempseed, menhaden, or sardine oil may be used instead of the perilla oil. The perilla oil, however, has considerably better drying properties than the other oils mentioned.
Gilsonite, when fluxed with raw tung or oiticica oil, gives an unstable liquid, that is, one which will take on excessive body when aging, and one which is not gas-proof. I
On the other hand, when gilsonite is fluxed with tung or oiticicaoils which have been heat-treated with the additions of gums or resins in the ordinary fashion, the resulting paint becomes full of check marks and deteriorates rapidly, particularly upon exposure.
The use of the present type of oils, however, results in a paint which does not take on excessive body upon aging and at the same time does not check and deteriorate rapidly upon exposure.
Driers, such as lead, cobalt, or manganese oxide, or the like, may be incorporated to control the drying time of the finished paint. Thinning oils such as mineral spirits, solvent naphtha, or any good solvent for the gilsonite and the oils, may be incorporated to bring the paint to the desired consistency. This normally requires about 50% to 65% by weight of thinning oils.
As an example of the invention, 50 pounds of gilsonite and 10 pounds of perilla oil are heated to a temperature of 400 to 450 F. and are mechanically agitated until the gilsonite is completely fluxed by the perilla oil. Forty pounds of the gas-proofed tung or oiticica oil (or a mixture thereof) are then added and mechanically mixed until the oils and the gilsonite are completely incorporated into a homogeneous mass. Thinning oils may then be added to bring the paint to the desired consistency, which normally requires about 53% to 55% of the thinning oils. The driers may then be incorporated in the desired percentage.
The percentage of ingredients may, of course, vary within rather wide limits, depending upon the particular characteristics desired in the ultimate product. For example, the percentage of gilsonite in the paint base may vary from 10 to 80%, according to the intensity of the color and the hardness of the film desired. Normally this ratio will be between 25 and 60%. However, for water-proofing on certain interior surfaces it is desirable to have a much harder film, and for certain of such uses it may be desirable to increase the gilsonite to as much as 80%.

Paint pigment

While the lower limit of 10% for the gilsonite is lower than will ordinarily be used, a satisfactory and durable paint may be made With as small a proportion of gilsonite as this by incorporating a small amount of carbon black, say 3%,; to 5% by Weight. 7
The percentage of tung or oiticica oil may likewise vary, but the higher the percentage thereof, the more durable will be the film produced. The preferred range is between 25 and 50% of either tung or oiticica oils, or a mixture thereof. However, the beneficial results of the combination of these gas-proofed oils with gilsonite are obtained over the entire range of Gilsonite concentration given.
In the above percentages any difference is normally made up by a viscosity reducing oil such as perilla. In the absence of such an oil, however, the tung or oiticica oil may be used to complete the paint base.
Pigments such as iron oxide, or chrome green may be incorporated to produce paints of attractive colors and great durability.
A paint prepared in accordance with this invention not only has greater water and Weather resisting properties, but is more resistant to acids and alkalis than a paint comprising gilsonite and a drying oil other than the gas-proofed tung oil.
The term film-forming constituents as used in the claims denote those portions of the film which do not evaporate following application of the paint, but which remain to form the paint film.
The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible in view of the prior art.

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