Silvering Glass.—In all cases where it is intended to deposit a silver mirror on a glass surface, thorough cleaning is essential. Prolonged soaking in a hot solution of potassium bichromate which has been acidified with sulphuric acid will often prove useful. The glass should then be washed thoroughly, rinsed in distilled water, and the solution should then be used.
There are many formulæ for the silvering solution, but that used in Martin's method may be given:—
| A—Nitrate of Silver | 40 | grammes |
| Distilled Water | 1000 | c. cm. |
| B—Nitrate of Ammonium | 60 | grammes |
| Distilled Water | 1000 | c. cm. |
| C—Pure Caustic Potash | 100 | grammes |
| Distilled Water | 1000 | c. cm. |
| D—Pure Sugar Candy | 100 | grammes |
| Distilled Water | 1000 | c. cm. |
| Dissolve and add:— | ||
| Tartaric Acid | 23 | grammes |
| Boil for ten minutes, and when cool add:— | ||
| Alcohol | 200 | c. cm. |
| Distilled Water to | 2000 | c. cm. |
For use take equal parts of A and B. Mix together also equal parts of C and D in another vessel. Then mix both liquids together in the silvering vessel and suspend the glass to be silvered face downwards in the solution. Or if a vessel has to be silvered on the inside, the solution is poured in. In this case, the deposition of silver may be hastened by immersing the vessel to be silvered in warm water.
In working with a silver solution containing ammonia or ammonium salts there is sometimes the possibility of forming an explosive silver compound. It is well, therefore, to avoid keeping such solutions longer than is necessary, and to bear in mind that any deposit formed by solutions containing both silver and ammonia may have explosive properties, especially when dry.
CHAPTER V
Extemporised Glass-Blowing Apparatus—The Use of Oil or other Fuels—Making Small Rods and Tubes from Glass Scrap—The Examination of Manufactured Apparatus with the View to Discovering the Methods Used in Manufacture—Summary of Conditions Necessary for Successful Glass-Blowing.
If, in the early stages of his study of glass-blowing, the student should attempt to work with the very simplest appliances, it is probable that his progress will be hindered; the use of the apparatus will require an undue amount of care and his attention will be distracted from the actual manipulation of the glass. The case is widely different after he has acquired a certain facility in glass-blowing.