154 ON THE VULCANITE BASE 



This, we tliink, answers the inquiry, so often 

 made, — " Will the material shrink ?" 



3rd. That the plaster models or moulds should 

 never be dried, and that the material should be 

 packed while the plaster is in its natural condition, 

 one hour or more after casting. 



4th. That no moisture should be allowed in 

 contact with the material while packing, and that 

 in removing work from the flasks, it should be first 

 allowed to become perfectly cold. 



In replacing teeth upon a set which has been 

 worn, by the addition of new material, I find that 

 the original changes to a darker brown, but gene- 

 rally loses none of its strength and solidity. 



If, however, the same piece had been continued 

 in the heat (at the first time of vulcanizing), the 

 additional time given to it in repairmg , it would 

 have been rendered brittle and wholly unfit for 

 use. 



This may be accounted for by the condition of 

 new plaster, which had been substituted for that 

 which had already been in the steam. 



Yet no one doubts, I suppose, but that the heat 

 is as intense in the centre of a flask at the moment 

 it is up to the point of vulcanizing, as when the 

 piece may have remained in double the time neces- 

 sary for making good work. 



I have made numerous experiments, in com- 

 bining with plaster for moulds proportions of 



