174 GOODYEAR ON GUM-ELASTIC. 



the practical difficulties that were met with in it, particularly 

 those of blistering and fermentation, after the art of vulcaniza- 

 tion was discovered. The fermentation of the compound and 

 the impossibility at first of heating the fabrics evenly without 

 their being blistered, presented the chief obstacles in the way 

 of success. Owing to these, and the want of means to obtain 

 suitable heating apparatus, it was more than a year before 

 specimens could be produced sufficient to satisfy any one that 

 there was any value in the invention. And after the man- 

 ufacture was established by those who had ample means for 

 experimenting with every facility, the discouragements in this 

 art of heating were so many, and ihe actual losses by goods 

 that were damaged were such, that for a period of three or 

 four years more, or until 1845-6, it was considered by most 

 persons to be exceedingly doubtful whether the invention could 

 be made so practicable as to become generally useful ; and 

 these doubts of the success of the manufacture were not 

 wholly removed until the gum came to be ground and 

 worked with steam heat, instead of being dissolved with tur- 

 pentine. 



During the first year or two, the writer worked the gum 

 always by dissolving it, and used chiefly the machinery with 

 which the compounds are spread by the straight edge or 

 knife, by which method the compounds are much more liable 

 to fermentation on account of the greater quantity of turpen- 

 tine that has to be used to make the gum liquid enough to be 

 spread by this machinery. 



This tendency of the compounds to ferment, particularly in 

 those in which lead, litharge, vermilion, and chrome are used, 

 occurs in hot weather, and also in cold weather when the 

 compound is kept in a warm place ; and if not spread within 

 a day or two after it is mixed, it ferments or sours, and can 

 not be vulcanized. As no one at first had any knowledge or 

 suspicion of any such change in the composition, and as it 

 did not always occur when the circumstances were apparently 

 (though not really) the same, it was the occasion of much per. 



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