55 G ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



DE LA BASTIE's EXPERIMENTS IN TEMPERING GLASS. 



De la Bastie,tbe inventor of the process for the tempering 

 of glass, whereby its strength is increased and its brittleness 

 removed, states that all liquids are not suitable for the pur- 

 pose ; that it is necessary by experiment upon each of them 

 to determine those which insure the success of the operation, 

 and anions: these even a choice will still have to be made. 

 Some in fact double, others quadruple, and others even ten- 

 fold increase the solidity of the glass. The maximum strength 

 possible has been determined by Siemens, of Dresden, to be 

 about fifty times that of ordinary glass. Bastie has himself 

 determined for every liquid the co-efficient of its strengthen- 

 ing power. Three elements concur in the determination of 

 this co-efficient : First, the composition of the bath, which is 

 never formed of a single liquid. Secondly, the proportion in 

 which each material enters into its composition ; and, finally, 

 its temperature. This last element is not that which has de- 

 manded the least amount of study. At one degree of tem- 

 perature the glass becomes brittle, instead of being temper- 

 ed. At another temperature it acquires solidity, and at still 

 another it may attain its maximum of solidity. There are 

 also other considerations. The proper temperature of the 

 bath will vary according to the chemical constitution of the 

 glass, and according to the oxides which enter into its fabri- 

 cation : the different temperatures needed for either of two 

 different glasses may vary to the extent of 200 Centigrade. 

 If one calculates all the combinations which have to be made, 

 in order to determine by purely empirical means the most 

 favorable conditions to success, taking account of the various 

 elements, the composition of the bath, the preparation of the 

 various liquids which compose it, the thermometric state, the 

 chemical constitution of the various glasses, etc., we shall not 

 be astonished that this study has demanded many years of 

 work, which was not always without danger. As to the value 

 of his discovery, from an economical and industrial point of 

 view, De la Bastie states that his researches have not been 

 conducted as an object of mere curiosity. His invention 

 leaves his hand complete in every respect, so that he is ready 

 to manufacture strong and malleable glasses of every kind, 

 for every purpose to which such material can be applied. 



