The free Nitrate of Silver increases the instability of the Gold salts; but if present in too great an excess, it is apt to cause a decomposition of Hyposulphite of Silver, and consequent yellowness in the white parts of the proof. It is therefore particularly recommended to wash the print in water before immersing it in the fixing and toning Bath. c. _Temperature of the solution._--In cold weather, the thermometer standing at 32° to 40°, the Bath works more slowly than usual; whereas in the height of summer, and especially in hot climates, it occasionally becomes quite unmanageable. The best temperature for operating successfully appears to be about 60° to 65° Fahrenheit; if higher than this the solutions must be employed more dilute. d. _Addition of Iodide of Silver._--Some operators associate Iodide with Chloride in the preparation of sensitive paper for printing. Another source of the same salts is the admixture of a portion of the fixing Bath used for Negatives with the Positive toning solution. The presence of Iodides in the fixing and toning Bath is injurious: when in large excess, they dissolve the image, or produce yellow patches of Iodide of Silver on the lights; in smaller quantity, the deposition of the Gold is hindered, and the action proceeds more slowly. Bromides and Chlorides have not the same effect. e. _Mode of preparing the paper._--The rapidity of toning varies with causes independent of the Bath: thus, plain paper prints are toned more quickly than prints upon albuminized paper, and the use of English paper sized with Gelatine retards the action. Foreign papers rendered sensitive with Ammonio-Nitrate tone the most quickly.