ZINC ETCHING 



6412 



ZINNIA 



and a number of oth in the 



United States, and in British Columbia. The 

 Joplin district in Missouri is the chief center 

 of zinc production in America, about sixty per 

 cent of the entire output of the country coming 

 from this district. The New Jersey mines are 

 next in importance. The United States pro- 

 duces over 480,000 tons yearly. 



Metallic zinc is obtained by roasting the ore, 

 which sets the oxide free in the form of a white 

 powder. The oxide is then heated with char- 

 coal, the operation being conducted in earthen 

 tubes or clay crucibles, which are connected 

 with an iron receiver in which the powder 

 finally condenses into a liquid. 



Uses. In the form of sticks and plates, zinc 

 is extensively used for the positive plate in elec- 

 tric batteries (see ELECTRIC BATTERY). Sheet 

 zinc is used for lining tanks, and for protecting 

 woodwork from heat when placed under stoves 

 and on walls. Zinc is melted with copper to 

 form brass and other bronzes and alloys, and 

 is employed in the production of galvanized 

 iron, which is made by dipping sheet iron in 

 molten zinc. It is also used in the process of 

 zinc etching (which see) for making plates used 

 in the reproduction of drawings in printing. 



Zinc White. Zinc white, a compound of zinc 

 and oxygen, is a white powder extensively used 

 in the preparation of a white paint for inte- 

 riors. Zinc white is manufactured by roasting 

 zinc ore and burning the vapor. The paint is 

 .prepared by grinding the powder in linseed oil. 

 Zinc white makes a purer white than white lead, 

 but it is not suitable for exteriors because it 

 discolors on exposure to the weather. 



Other Compounds. Zinc sulphate, or white 

 vitriol, occurs in white crystals which change 

 to powder when exposed to the air. It is used 

 in calico printing and as a disinfectant in medi- 

 cine. Zinc chloride, a compound of zinc and 

 chlorine, is extensively used to preserve wood 

 from decay. About 1,500 tons are used yearly 

 for preserving railway ties. W.F.R. 



Consult Ingalls' Production and Properties of 

 Zinc; Holley's Lead and Zinc Pigments. 



ZINC ETCH 'ING, a process of making a 

 plate for the reproduction of drawings and let- 

 tering. The drawing is made with India ink on 

 white paper. A photograph on glass is made 

 of the drawing. This photograph is clamped to 

 a highly-polished plate of zinc which has been 

 coated with wax or some other substance upon 

 which acid will not act, and then coated with a 

 sensitized solution similar to that used in mak- 

 ing plates for use in cameras. The zinc plate is 



then subjected to electric light or to sunlight 

 for a short time, and the pictures are trans- 

 ferred to the sensitized surface, which is etched 

 as in the production of a halftone. 



A zinc etching requires but a short time for 

 production and is an excellent process for the 

 reproduction of line drawings, but fine shadings 

 cannot be reproduced. A print from a zinc 

 etching consists of black lines interspersed with 

 white spaces. For the reproduction of photo- 

 graphs and other pictures in which it is neces- 

 sary to preserve the shading, one must resort 

 to the halftone process or some modification of 

 it. All the illustrations set into the printed 

 pages of this work are from zinc etchings. The 

 drawings were made in India ink, and were 

 twice the dimensions of the completed pictures. 

 See HALFTONE; PHOTOGRAPHY. 



ZINNIA, zin'ia, a genus of plants belonging 

 to the composite family, comprising about six- 

 teen species. The zinnias are native to Mexico 

 and the Southwestern United States, where they 

 secure an abundance of warm sunshine. The 



THE ZINNIA 



best-known species Zinnia elegans is a gar- 

 den plant that blooms in a wide variety of col- 

 ors. It has a stiff, hairy stem which may reach 

 a height of two feet. The flowers, made up of 

 numerous florets, appear in various shades of 

 red and yellow, including scarlet, crimson, pink, 

 salmon and bronze, but the florist never knows 

 whether these colors will be clear and brilliant 

 or dull and blurred. This element of uncer- 

 tainty in the flowering of the zinnia, in addi- 

 tion to its lack of fragrance, has detracted from 

 its popularity. 



