XLII 



THE INDIA RUBBER WORLD 



[July 



1903. 



WHAT THE BUYER SHOULD KNOW ABOUT 

 RUBBER GOODS." 



W! 1 1 LE it is impracticable for the buyer or user of rubber 

 goods to acquire a close knowledge of their manufac- 

 ture, there are some points which he should be familiar with, 

 and which are of great importance, considering the constantly 

 increasing variety of uses and kinds of rubber goods. The 

 quality of rubber articles can be chiefly determined by the 

 length of time for which they retain that elasticity, and in 

 other cases that firmness, which is necessary for the respective 

 purposes for which they are intended, without acquiring cracks 

 fractures, or other injuries, without softening, and without 

 hardening. These properties are due to the quality of the crude 

 rubber, as well as to the manufacture of the articles. The qual- 

 ity of crude rubber varies considerably, according to the differ- 

 ent varieties of trees from which it is obtained, and it is impos- 

 sible to say of a finished article from what kind of crude rubber 

 or what mixture of different kinds of crude rubber it is made. 

 For this distinction all auxiliaries are lacking and even an ex- 

 pert can only occasionally determine with absolute certainty 

 the presence of a certain variety of crude rubber. To this must 

 be added the fact that it is not possible in one and the same 

 factory to obtain at all times the identical variety of crude rub- 

 ber which they are wont to use. Since the supply is subject to 

 the arrivals and market fluctuations, it will not rarely occur 

 that rubber articles which are continually bought from the 

 same maker sometimes contain a different crude Caoutchouc 

 and exhibit varying properties in use. It is, of course, impos- 

 sible to tell this when buying the rubber, and it is usually 

 thought sufficient if the outward characteristics coincide with 

 those of the goods purchased before. 



Among the exterior properties of rubber articles that are 

 considered indicative of their quality is, above all, the color, 

 and in this respect the remark is often heard : " Red rubber is 

 the best." This opinion, which has no justification whatever, 

 is doubtless due to the handsome bright color of red rubber, 

 which possibly, in the beginning, was used by the salesmen to 

 recommend such rubber goods to the buying public and is 

 now kept up, lest the consumption might drop off owing to a 

 less favorable appearance of the article, for all other colorings 

 of rubber are more or less unsightly and impure looking. The 

 above judgment should, therefore, read : " Red rubber is the 

 handsomest." Red rubber was introduced at one time by the 

 manufacturers to a large extent because the coloring matter used 

 for its production, on the one hand was considered a good vul- 

 canizing agent, and on the other hand because this substance 

 — golden sulphur of antimony — imparts a brilliant red to the 

 rubber even upon admixture of a comparatively small quantity. 

 I( the quality could at all be judged by the color, the mouse- 

 gray rubber should be pronounced the best, because outside of 

 sulphur it does not contain any mineral admixtures. In con- 

 sequence this rubber is the most elastic, but whether it com- 

 bines the greatest elasticity with the greatest durability in 

 every case is a matter of conjecture, for additions of an organic 

 nature are also employed which frequently detract from the 

 durability in a worse way than the mineral substances. It is a 

 general rule that the elasticity of rubber increases with the de- 

 crease of its specific gravity, and particularly as regards elas- 

 ticity it should at least be lighter than water, and hence should 

 float on it. The firmness and toughness, such as are required, 

 for tires, is quite another question. In order to impart these 



qualities to rubber, large admixtures of mineral substances are 

 necessary ; hence for such uses a rubber of higher specific 

 gravity is of advantage. 



Beside by the composition, the quality of rubber articles is 

 governed by the nature and mode of their manufacture, or 

 rather the correct performance of the processes and manipula- 

 tion pertaining thereto. To judge whether the manufacture 

 has been carried out in a perfect manner, there are some im- 

 portant rules. Thus a rubber article should not receive a last- 

 ing impression by the pressure of the finger nail; the mark 

 should disappear immediately. If this is not the case, the vul- 

 canization has been imperfect and the material will quickly 

 deteriorate and become useless. When the rubber is cut the 

 cutting surfaces should not show any holes, however small, for 

 wherever they are present the rubber will wear off more rapidly 

 than in the compact, homogeneous portions, and many articles, 

 such as rubber rollers, are entirely unfit for use if they exhibit 

 any defective spots. These hollow spaces are caused by un- 

 skillful treatment of the Caoutchouc in vulcanizing and are 

 seldom confined to small parts of the respective object, but 

 usually extend over the whole, being evenly distributed and 

 sometimes occurring in the form of large blisters, in which 

 cases their action is naturally still more harmful. If this de- 

 fect is noticed in any rubber article, it must be regarded as in- 

 ferior. 



Furthermore, the so called seams in articles of rubber should 

 be only slightly visible. These are the places where the differ- 

 ent sheets or plates are joined together. If the seams are plain- 

 ly visible, and if upon stretching in the lengthwise direction 

 considerable depressions appear, the rubber is not joined per- 

 fectly and the seams will easily split, as is sometimes seen on 

 rubber hose. If the rubber peels off in layers, this is just as 

 harmful and due to the same causes. Thick articles are made 

 by cementing the layers one on the other. If this is not done 

 n a careful manner, and if substances get in between which 

 prevent mutual adhesion, the layers will become detached again, 

 especially in use, and it may occur that the rubber splits in 

 places thus becoming useless. It is also not infrequent that in 

 rubber articles with a lining of fabric (as strong hose) or rub- 

 ber lined goods the junction of the Caoutchouc and the fabric 

 is imperfect and that the two substances become detached in 

 places. This can be ascertained by sharply bending the respec- 

 tive article repeatedly, in various places and in different direc. 

 tions, when it can easily be felt whether the Caoutchouc and 

 the fabric become displaced. 



A GERMAN SUBSTITUTE FOR CELLULOID. 



* Translated for The India Rubbbr World from the Zeilschrift fur die Ges- 

 amte Kohlensiure-lndus'.rie (Vienoa.) 



THE United States consul general at Coburg, Mr. O. J. D. 

 Hughes, reports to his government under date of Octo- 

 ber 1 1, 1902 : 



" The extensive commercial use of celluloid has caused a 

 great many people to try to find substitutes for, or imitations of, 

 it. In this part of Germany, a popular imitation has been made 

 by dissolving in 16 parts— by weight — of glacial acetic acid, 1.8 

 parts of nitrocellulose, and adding 5 parts of gelatin. Gentle 

 heating and stirring are necessary. After the mass has swollen, 

 it is mixed with 7.5 parts of alcohol (96 per cent.), and stirring 

 is continued. The resulting product is poured into molds, or, 

 after further dilution may be spread in thin layers on glass. 

 As an underlay for sensitive photographic films, the material 

 has important advantages, not the least being that it remains 

 flat in developing." Information regaiding this material has 

 yet to come through trade channels, but one would expect Ger- 

 man chemists to be first to attempt a substitute for celluloid. 



