ULTRAMARINE BLUE AND WASH BLUE. [Par. 52, act of 1913, 15% ad valorem.] SUMMARY. Ultramarine is the most important blue pigment. The commercial product is manufactured in a variety of grades, all having similar chemical composition and difficult to distinguish by laboratory investigation. A practical application to the purpose for which it is sold seems to be the only criterion of value since the properties depend upon the mechanical preparation of the product. Ultramarine is used not only for painting and in printer's inks, but also for coloring soaps and laundry blue. It is also used in small quantities to neutralize the yellow color in paper pulp. Green, yellow, violet, and red varieties of ultramarine are manufactured, but none of the colors, except blue, are consumed in any but small quantities. The chief raw materials required in the manufacture of ultramarine are soda ash (sodium carbonate), China clay, carbon, and sulphur. There is also a method of manufacture in which Glauber's salt is substituted for the soda ash and sulphur. The fuel requirements are fairly large. Domestic manufacturers are not handicapped as regards their supply of raw materials or fuel. Extremely pure materials are necessary, but these can be obtained as cheaply in this country as in most foreign countries. Labor, however, is a much more important item of cost in the manufacture of ultramarine than it is in the case of most pigments. The domestic output is furnished largely by one producer, although there are several smaller establishments, and in 1914 about one-fourth of the total domestic consumption was imported. Prior to the war imports were derived chiefly from England and Germany. Other European countries have furnished only a small fraction of the foreign ultramarine sold in the domestic market. 1 Six months ending June 30, 1920. GENERAL INFORMATION. Paragraph 52, of the act of 1913.-"* * * ultramarine blue, whether dry, in pulp, or ground in or mixed with oil or water, and wash blue containing ultramarine, 15 per cent ad valorem.” DESCRIPTION. Ultramarine is the most important blue pigment.' It occurs in nature as the mineral lapis lazuli. But the natural mineral is very rare, being classed with the semiprecious stones, and is of no importance as a pigment. The ultramarine of commerce is an artificial product of the same composition as the natural mineral and is sold. in the form of a bright azure-blue impalpable powder that is not soluble in water. Chemically, ultramarine is a double silicate of sodium and aluminum and containing a little sulphide. Different samples of the same physical qualities, however, often differ slightly in composition. A pure white ultramarine is supposed to be the base of the whole series of colored compounds. Its formula is given as Na,Al,SiO,.Na,S. The common blue variety is believed to vary from a soda ultramarine, poor in silicia-4(Na¿Al¿Si2O).Na,S,-to a modification containing high silica-2(Na2Al„Ši ̧Ó1).Na,S. Green ultramarine is probably not a distinct chemical compound but a mixture of other ultra marines. Yellow, violet, and red varieties of ultramarine have been produced, and green ultramarine is an intermediate product in the manufacture of blue ultramarine according to one method. None of these, except the green, have any commercial importance, as they have little tinctorial power and are generally more expensive than better pigments of like shade but having a different composition. USES. Ultramarine blue is much used in wall paper for neutralizing the yellow in paper pulp and cotton and linen goods, for laundry blue (bluing), for coloring mottled soaps, and as a general pigment in lithographic ink and in paint. Only the better grades are used in I Thorp. Outlines of industrial chemistry. Macmillan. 1916. artists' colors, coach and car colors, and in printing. Sand colored by ultramarine is sometimes used as an imitation for smalt—a potashcobalt glass. SUBSTITUTES. Ultramarine has largely replaced most of the cobalt colors in painting and can be used with zinc white as a tint. Prussian blue, however, is generally preferable and is always employed as the blue constituent of greens obtained by mixing blue and yellow pigments. These two colors, ultramarine and Prussian (and other ferrocyanide) blue, are now practically the only commonly used inorganic blue pigments. There is a growing use of lakes, but these organic (largely coal-tar) colors are generally less permanent. The choice between ultramarine and ferrocyanide colors depends upon whether or not resistance to alkalies is required. Both are permanent to light when used alone and are obtainable at about the same range of prices and grades. Utramarine is not affected by alkalies, but is affected by (or, perhaps more properly, does affect) lead compounds. The ferrocyanide colors are destroyed by alkalies (cf. soaps), do not react with lead compounds, and are a trifle less resistant even than ultramarine to acids. Neither pigment, however, is satisfactory when exposed to acid fumes. PRODUCTION. General. The annual world production of ultramarine (in 1913) was from 10,000 to 15,000 tons, valued (on an average) at something less than $150 per ton. There are at least 100 factories, mainly in Germany and France, although a few are in England, Austria, and the United States. The development of this pigment has been remarkable. The process for making the artificial variety was discovered in 1828. When first placed on the market, the price was 16s. (about $3.90) per pound. But later, competition resulted in a quite rapid reduction, both in price and in cost of manufacture. Factories were established in Cologne and Nuremburg between 1830 and 1840, and from 9 to 12 new factories appeared in various parts of Europe in every succeeding decade.1 Raw materials. The materials used in making ultramarines are China clay or other high-grade pottery clay, soda ash (carbonate), or Glauber's salt (sodium sulphate), carbon (charcoal, lampblack, etc.), sulphur, and sometimes kieselguhr, diatomaceous earth, or other silicious matter. All materials entering into the manufacture of ultramarine must be selected with care. High purity is essential for making a product of suitable color. Iron, especially, is likely to make the product dull; hence the clay must be carefully washed and only grades of soda that contain no iron salts can be used. When sodium sulphate is employed, it must not contain free acid. Process of manufacture. Ultamarine may be manufactured by either of two processes, (1) the direct method which uses soda ash, or (2) the indirect method in which the requisite soda is supplied by Glauber's salt. Both processes involve furnace treatment. 1 Data in this paragraph from Thorpe's Dictionary of Applied Chemistry. (1) The direct process yields blue ultramarine as the first product, but is extremely slow. The fusion is conducted in muffles or crucibles. The former are generally more economical, although their slow cooling-taking 10 to 12 days somewhat adds to the time of the process. Three or four weeks are required for the treatment of a single charge in one of these muffles, which generally takes about 21 tons per charge. Smaller quantities are handled in crucibles, and the extra labor involved, together with the breakage, more than offsets the less time required in heating and cooling off. The raw materials, consisting of soda ash, clay, charcoal, and sulphur, are mixed in proper proportions and finely ground. They are charged into a cold furnace and packed firmly into crucibles or tamped down on the floor of a muffle in a layer about 14 inches thick. Before heating, the charge must be covered up and luted air-tight. Access of air at any time until after the reactions are completed and the furnace is cool will ruin the product. During the heating process, the chief operation aside from firing the furnace is the covering up of cracks, etc., in order to prevent the entrance of air. At the conclusion of the fusion and after the furnace is cool, the charge is found to be in two layers, the top bright blue and the bottom greenish blue. These are separated, washed, ground, and levigated. The washing removes soluble salts. Because of the considerable amount of water glass (sodium silicate) which must be removed, soft water must be used in washing and grinding operations. The pulp, after grinding, is run into settling vats, where it settles according to the varying degree of fineness. The very highest qualities require several days to settle out from the water. The levigation is a most important stage of the process and requires great care and attention. The bulk of the blue settles out in from 36 to 48 hours, but it must then be shoveled out and resettled. As each batch is slightly different from the preceding, blending is a necessary adjunct to the production of standard shades. (2) The indirect process yields green ultramarine as the first product and is a much quicker process than the direct method. The first fusion differs from the direct operation chiefly in that soda ash and sulphur are replaced by sodium sulphate. The sulphate requires a little more coal or charcoal in the charge (as it must be reduced to sulphide in the fusion). Rosin is sometimes used as a reducing agent. The heating, which is generally conducted in crucibles, takes about eight hours, but the slow cooling of the furnace adds several hours more to the treatment period. After cooling, the mass is green and porous. It needs only to be washed free from impurities and ground for sale as ultramarine green. To make blue ultramarine, the green powder is roasted with sulphur. The heating is done in open pans or muffles and the charge is stirred mechanically. It is probable that a part of the sodium sulphide is oxidized to soluble sulphate during the heating and thereby removed from the combination with the silicates. The extent of this change is regulated by adding sulphur from time to time. The cooled blue product is ground and levigated. In making the cheaper brands of ultramarine blue, the pure color is mixed with gypsum. This adulterant is sometimes added in amounts up to 50 per cent. It has an extremely bad effect on the brightness of the color of certain varieties of ultramarine, but the effect is minimized by the addition of a little glycerol or vaseline to the mixture. Equipment. In addition to the usual equipment for grinding and mixing raw materials and for the preparation of the finished pigment considerable furnace area would seem to be required for the making of ultramarine. The furnaces, however, are of simple construction and can be made of local brick. DOMESTIC PRODUCTION. The census figures show an output of 2,698,639 pounds of ultramarine, valued at $222,769, in 1914. IMPORTS. Quantity. The imports of ultramarine in the fiscal year 1914 were the largest on record, amounting to 901,203 pounds, valued at $78,392. It is worthy of note that the imports of ultramarine from July to September, 1913, under the act of 1909 were about equivalent in volume to the imports in the nine months of the fiscal year 1913 under the act of 1913. About 40 per cent of the revenue collected during the year, however, was obtained from the imports during the first three months under the act of 1909. The average annual importation of ultramarine for the eight preceding years (1906-1913, inclusive) was approximately 700,000 pounds, valued at $63,438. Throughout this period the variation in the amount and value of the imports from year to year is noticeably small; but in 1906, the first year of the period, there was a sharp increase, amounting to over 50 per cent, as compared to the preceding year and similarly, as compared with the average yearly imports for the 10-year period, 1896 to 1905. That decade is also remarkable for the slight yearly variations from the general average importations 416,651 pounds, valued at $45,950, annually-for these years. It is a coincidence that this period, like the one that succeeded it, was ushered in by a radical fluctuation in the amount and value imported. The change in this instance, however, was a reduction. The imports in 1896 were almost 50 per cent less than the imports in 1905.1 Since the outbreak of the European war the imports of ultramarine have decreased gradually. In 1918 (fiscal year) less than 360,000 pounds were imported. Wash blue, containing ultramarine, is listed separately in Commerce and navigation. The imports are small in amount and register a gradual decrease both in quantity and value until 1914. Less than 100,000 pounds were imported in 1913. Since October 3, 1914, when an ad valorem duty was adopted, the quantities of wash blue imported have not been published by the Department of Commerce. The values, however, show a rapid decrease from 1914 to 1916 in The fiscal year 1895, however, was a year of abnormal imports, following immediately after the reduction in the duty on Aug. 28, 1894. |