Jasper County Democrat, Volume 13, Number 20, Rensselaer, Jasper County, 15 June 1910 — MODERN BALLOONS. [ARTICLE]

MODERN BALLOONS.

Gas Bags Made of Cotton Coated With Rubber. The gas bags of modern balloons are made of a cotton fabric coated with India rubber in the most careful manner, in order to assure perfect imper meability without sacrificing lightness For all large balloons, and especially for dirigibles, two layers of clpth are superposed and cemented together. The outer skin is covered with India rubber on one side only, but the inner skin is coated on both sides. In German balloons the inner canvas is cut straight and the outer canvas is cut bias. In this constructed gores with angles of 45 degrees are used and the seams 1 are covered, which causes a slight increase in weight. French balloon makers prefer to cut both canvases straight. Experiments show that the tensile strength of the envelopes thus made is approximately equal in all directions. Each method of construction has its advantages and its defects, says the Scientific American. As India rubber, even when vulcanized, is altered by exposure to light, the canvas is colored yellow in order to arrest the violet and ultraviolet rays, which are the most active. The pigment used in France is chromate of lead, which unfortunately must be applied to the canvas before it is coated with rubber, and which consequently prevents the vulcanization of..the rubber, because the chromate of lead is blackened by heat. Picric acid is free from this objection, but its employment is too dangerous.