882 



STAMPING OF METALS 



the rays of light from their numerous surfaces, exhibit through the glass, richly 

 stained with gold, silver, copper, cobalt, &c., a gorgeous play of prismatic colours, 

 varied with every change of aspect. When the enamel is to be painted on, it should 

 be made opalescent by oxide of arsenic, in order to produce the most agreeable effect. 



The blues of vitrified colours are all obtained from the oxide of cobalt. Cobalt ore 

 (sulphide) being well roasted at a dull red heat, to dissipate all the sulphur and 

 arsenic, is dissolved in somewhat dilute nitric acid, and after the addition of much 

 water to the saturated solution, the oxide is precipitated by carbonate of soda, then 

 washed upon a filter and dried. The powder is to be mixed with thrice its weight of 

 saltpetre ; the mixture is to be deflagrated in a crucible, by applying a red hot cinder 

 to it, then exposed to the heat of ignition, washed and dried. Three parts of this 

 oxide are to be mixed with a flux, consisting of white sand, borax, nitre, and a little 

 chalk, subjected to fusion for an hour, and then ground down into an enamel-powder 

 for use. Blues of any shade or intensity may be obtained from the above, by mixing 

 it with more or less flux. 



The beautiful greenish-yellow, of which colour so many ornamental glass vessels 

 have been lately imported from Germany, is made in Bohemia by the following process : 

 An ore of uranium, as Uran-ochre, or Uran-glimmer, in fine powder, being roasted and 

 dissolved in nitric acid, the filtered solution is to be freed from any lead present in it 

 by the cautious addition of dilute sulphuric acid. The clear green solution is to be 

 evaporated to dryness, and the mass ignited till it becomes yellow. One part of this 

 oxide is to be mixed with three or more parts of a flux, consisting of 4 parts of red lead 

 and 1 of ground flint ; the whole fused together and then reduced to powder. 



Chrome-green. Triturate together in a mortar equal parts of chromate of potash and 

 flowers of sulphur ; put the mixture into a crucible and fuse. Pour out the fluid mass ; 

 when cool, grind and wash well with water, to remove the sulphuret of potash and to 

 leave the beautiful green oxide of chrome. This is to be collected upon a filter, dried, 

 rubbed down along with thrice its weight of a flux, consisting of 4 parts of red lead 

 and 1 part of ground flints fused into a transparent glass ; the whole is now to be 

 melted and afterwards reduced to a fine powder. 



Violet. One part of calcined black oxide of manganese, 1 of zaflfre, 10 parts of the 

 white glass pounded, and one of red lead, mixed, fused, and ground. Or gold purple 

 (Cassius's purple precipitate), with chloride of silver, previously fused with ten times its 

 weight of a flux, consisting of ground quartz, borax, and red lead, all melted together. 

 Or solution of tin being dropped into a large quantity of water, solution of nitrate of 

 silver maybe first added, and then solution of gold in aqua regia, in proper proportions. 

 The precipitate is to be mixed with flux and fused. 



STAMPING OF IVIETAIiS. The peculiar feature of improvement in the 

 manufacture of stamped articles consists in producing the spoon, ladle, or fork perfect 

 at one blow in the stamping machine, andrequiring no further manipulation of shaping, 

 but simply trimming off the barb or fin, and polishing the surface to render the article 

 perfect and finished. 



Formerly, in employing a stamping machine, or fly-press, for manufacturing 

 spoons, ladles, and forks, it was the practice to give the impression to the handles, 

 and to the bowls or prongs, by distinct operations of different dies, and after having 

 BO partially produced the pattern upon the article, the handles had to be bent and 

 formed by the operations of filing and hammering. 



By Mr. Haynes' improved dies, which, having curved surfaces and bevelled edges, 

 allow of no parts of the faces of the die and counter-die to come in contact, he is 

 enabled to produce considerable elevations of pattern and form, and to bring up the 

 article perfect at one blow, with only a slight barb, or fin, upon its edge. 



1887 



1889 



188H 



In the accompanying drawings, fig. 1888 is the lower or bed die for producing a 

 spoon, seen edgewise ; fig, 1 887 is the face of the upper or counter die, corresponding ; 



