Figure 35.
The soldering is protected by placing a paste made of yellow ochre and water about the soldered joint both inside and outside of the strip. The more of this clay we bank about the joint the more protection there is. When the above has been done, the object must be left in some warm place until the moisture from both the enamel and the clay is thoroughly evaporated. It is then ready for firing. If the blow-pipe or the Bunsen burner is used, take a tripod and place a piece of heavy iron netting over the top and place the object on top of the netting. The flame should always be applied to the under side. Watch the enamel as the firing goes on and when it settles and glazes the heat should be withdrawn. The object should be allowed to cool very slowly. Hurrying at this point only increases chances for accidents. If, when cool, it is found that the channels in places are not full of enamel, the object is again cleaned in the nitric acid, more enamel applied, and fired as at first. The cover is now ready to finish. The enamel may be stoned down level with the top with an emery stone, or it may be left just as it comes from the fire in the first place. If stoned down, it is necessary to fire it again just enough to give it a glazed surface.
The directions as given apply to either transparent or opaque enamel; but, in addition to the above, when transparent enamel is used, the surface to be enameled must first receive a coating of flux to retain the transparency. The flux is treated and applied just the same as the enamel already described.
The upper half of [Plate 26] shows boxes treated with enamel.