Proceedings of the Polytechnic Association. 905' 



EXAMELED IkOX. 



Specimens of enameled' sheet iron witli colored lettering and 

 pictures by means of a cheap process recently bronght out in England. 

 They were exhibited by Mr. B. Austin, one of the agents in this 

 city. He said the enamel isput on with a brush, and is permanent, 

 not glazed over. Signs, such as exhibited, have been exposed to the 

 atmosphere in England for six and seven years without showing any 

 deterioration. Any class of pictures can be produced by this process. 

 The pictures are made by transfers, the colors are metallic oxyds, 

 and are burnt in at about 2800 degrees. lie exhibited a sheet of 

 enameled iron which had been kept in nitric acid for four months 

 which did not appear to be affected by acid pei'ceptibly. 



Dr. J. J, Edwards said that this was simply a good, practical, 

 cheap process of the old system of enameling, using iron instead of 

 copper. For interior work these enamels are very valuable. 



Mr. C. E. Emery stated he had recently experimented 'with speci- 

 mens of enamel, and found tliat some varieties of it wouhl crack 

 very readily, while others could be bent backward and forwai-d 

 without showing any fractures. The proportions and character of 

 the ingredients used in compounding the enamel make a great difiei-- 

 ehce with its elasticity. His experiments were more particularly 

 directed to the enameling of the cylinders of steam engines. The 

 cylinders were of cast iron, and were treated in the usual manner to 

 two coats of enamel ; the first of a softer, less refractory nature, sim- 

 ply filling the pores of the iron and forming a base for the glossy 

 exterior coat. He at first put on several coats to get a thick vitreous 

 surface. This was found to crack much faster than thinner coatings. 

 The thick coating was desirable for the reason that the cylinders 

 would spring out of shape when subjected to the high heat necessary 

 to melt the enamel, and the wearing surfaces inside could only be 

 made approximately true by careful grinding in a lathe. In some 

 cases the outer coating was completely gruund away and tiie under 

 coat exposed. The steam did not dissolve the enamel proi)er, but 

 attacked the inner coating. The thick enamel always cracUed on the 

 concave surfaces, but the arch form kept it in place a long time. On 

 the flat surfaces the enamel adhered well, except when the steam struck 

 its edge, and all difficulty of this kind was prevented by rounding the 

 corners where the steam entered. The object in using the enamel in 

 steam cylinders was to produce economy of steam and fuel by pre- 

 venting the condensation which takes place on account of the differ- 



