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572 in oil it thickens and _ eventually hardens. A theoretically correct for- mula for making up red lead paint is as follows: : Red lead, lbs...... Polliees Soh aie Wiciuinie se wanes ek ee 20 ONY TAUBO PU Gils DIIES sie oda. <'o'p 0's 0 oo Sos gi aie sie 5 Petroleum spirits, gills..... Beg Pek ce oie ince aera aie 2 rier pills see. SEs Tee Cees es See ey 2 This material makes pounds 4 ounces. If allowed to stand this material will harden as the red lead is precipitated but any first class paint manufacturer can supply red-lead paint having no injurious ingredients that will remain in a liquid state for many months. iron oxide, Fe,Q,,. is sometimes used as a base for marine paint. This material is obtained as a steel-gray crystallized powder by igniting the oxide of any ferric salt containing a Volatiie <acid.. Small crystals. are formed by passing ferric chloride over heated lime. When finely ground, these crystals yield a brownish red: powder. There is some authority for the use of this material based on the Strength of the claim that since it is used in connection with iron or steel, it is impossible for a galvanic couple to' be formed between the paint and the ves- sel's underbody. White lead is an- other by-product of metallic lead and is prepared. for the painter in sev- eral ways. The one att ae eee Ea oi HOW THE PAINT SPRAYING MACHINE IS -the desired shades. 'are umbers, USED TO THE MARINE REVIEW most commonly used, the English method, is in brief as follows: Sheet lead in coils is placed in jars with dilute acetic acid, the jars being placed in stacks and surrounded with fermenting tanbark. . 'After about three months, the lead is removed and put through a purifying process. The whole process is. slow but productive of white lead of excellent quality. The white lead of commerce common- ly contains 75 per cent carbonate of lead and 25 per cent lead hydrate. It is generally supplied to the painter in paste form mixed with 6 to 7 per cent by weight of linseed oil. White lead is an easy material to adulterate as it cannot be tested without elabo- rate laboratory apparatus. The chief adulterant used is sulphate of baryta. White zinc, which is made in much the same manner as white lead, is used for interior ship painting as it possesses the quality of permanency, is not expensive and is easily applied. White zinc, however, is not as desir- able for exterior painting as white lead. Orange mineral is a by-product of white lead made by roasting dry powdered white lead. The carbonic acid is decomposed by heat and driven off and the resulting material is roasted into a high grade red lead of an orange-red color. This product is considered by many to be equal in quality to the best red lead. When mixed as paint, the above materials beside acting as a_ base perform tthe additional function of supplying the pigment. Where other colors are desired, pigments of. vari- ous kinds are mixed with the paint until the desired shade is attained. As. a_ practical illustration, camouflage painting calls for a number of pigments to give The pig- ments commonly used in paint siennas, ochres, chromes, Venetian red, Indian red, lamp black, bone black, ADVANTAGE IN THE previously been heated. It December, 1919 ultramarine, Prussian vegetable black, and vandyke. blue, vermillion, lakes brown. The most commonly used vehicle for ship paint is Inseed oil. This material is extracted by hydraulic pressure from flax seed which has has: a transparent amber color and in this state is known as raw. oil. It is much improved by keeping. "Boiled" oil is raw linseed' oil heated to a tempera- ture of from 350 to 500 degrees Fahr. in which state it is kept for about four hours. During the process driers are added. This material is thicker and: of a darker c-lor than raw. oil. It drys quickly with a hard glossy coat which is less elastic than when raw oil is used. Solvent is added to paint for the purpose of keeping it moist long enough to set flat and evenly. Dur- ing the settling process, brush marks gradually disappear. The principal solvent used in ship paint is turpen- tine. This material, which is distilled from the sap of the pine tree, is de- rived from tthree sources, the United States, France and Russia. The high- est grade of turpentine comes from this country, French turpentine is next in quality while the Russian product is the poorest. Owing to the scarcity of this material, it is com- paratively expensive. As its name implies, drier is added to paint to' cause it to 'dry quickly. Thus the surface hardens before the paint has had time to take up too much dust from the _ surrounding atmosphere. Paint driers are made of lead and manganese compounds dissolved in oil. Resin is sometimes SHIPYARD ASIDE FROM ACTUAL WORK ON VESSELS--PAINTING A COLUMN