MISCELLANEOUS PAPERS. 363 



clear up, it is ready for the filter. If the solution clears, however, 

 more of the reserve silver must be added, as it is useless to attempt to 

 silver with an excess of ammonia. 



In filtering, a little cotton may be placed in the funnel instead of 

 filter-paper, which is slower and no more efficient than the cotton. 

 Having filtered into the vessel for final mixing, pour in about three 

 and one-half ounces of the reducing solution and wait a few moments 

 until it begins to turn a dark or black color. Meanwhile, pour into 

 the paraffined mirror-vessel as much distilled water as is thought nec- 

 essary to cover the surface the required depth. About a pint and a 

 half to a quart is sufficient. Pour in the silvering solution, and move 

 the glass near the edge of the table, where it may be tipped this way 

 and that, to keep the sediment of the silvering solution from settling 

 upon the surface, and thus interfering with the silvering. Within 

 five or six minutes the silver will begin to deposit, and in from ten to 

 fifteen minutes the process will be complete. If the ammonia has 

 not been in excess, the coat should be so thick as not to admit the 

 light when held before a window. If left in too long, the coat may 

 receive a tarnish that will be difficult to polish away. If the process 

 has been completely successful, this coating will be thick and bril- 

 liant. 



Pour the solution into a vessel and throw away, or precipitate as a 

 harmless chloride by adding common salt. A dangerous explosive may 

 form from this mixture, especially if the solutions be too warm. A 

 temperature of about 60 or 65 deg. F. is best for solutions and vessels, 

 as the silver will not deposit well if too cold. 



Cut the cords binding the paraffined paper and wash the sediment 

 carefully from the silvered surface with clean water. The surplus 

 water may be allowed to drain away. The drying process may be 

 hastened by absorbing the moisture from the silver by carefully ap- 

 plying clean blotting paj^er, being careful not to slide the paper. 

 After ten or fifteen minutes the surface should be ready to polish, but 

 the operator must be certain no moisture remains. Three or four pads 

 of the softest and smoothest chamois skin should be at hand, stuffed 

 lightly with cotton. Taking one of these in the hand, rub lightly at 

 first, in spira-l strokes over the surface, gradually increasing the firm- 

 ness of the pressure. This polishing is simply to clear away the 

 loose foreign substances remaining from the washing, and to give a 

 firmness to the silver surface. It should, however, give a fairly good 

 mirror surface from this rubbing. For the final polishing rub into 

 another pad a little polishing rouge, brushing off the surplus rouge. 

 Now go over the surface with the rouged pad until a brilliant surface 

 is obtained. As long as the silver coating remains it will not injure 



