This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Washing After Toning In Gold Bath. As the prints become toned place them in a tray of fresh water, using plenty of solution. As you proceed with the toning, occasionally pick over the prints in this tray of fresh water. After the entire batch is toned it is absolutely necessary that they should receive a thorough washing to remove all the excess alkali from the prints. The gold bath being alkaline, there will be considerable of this alkali carried into the first wash water.
197. Give the prints three changes of fresh water, thus eliminating all the excess alkali, when they are ready for the platinum bath. If the prints were placed in the platinum bath in an alkaline condition they would very-soon fill the bath with alkali, consequently causing the platinum to precipitate. In a short time all the platinum precipitated in the form of a sediment would settle on the bottom of the tray, and the prints would refuse to tone even if more platinum is added. Should you be successful, however, in forcing a tone in this bath by using a strong platinum solution, the result would probably be yellow, muddy prints when mounted, as they will surely show up sooner or later. After freeing prints from excess alkali they are ready for the platinum bath, which should be prepared at least one hour previous to using.
Toning In The Platinum Bath. When the prints first go into this bath the highlights become muddy, but within a short time they commence to clear. Prints must remain in the bath until the whites are thoroughly cleared and every trace of red and brown is removed in the deepest shadows. Do not fear leaving the prints in the platinum bath until the desired color and richness you desire is obtained.
199. A slow working platinum bath gives olive tones and flattens the whites, while a quick platinum bath gives black tones. A slow bath has a tendency to cause the shadows to become muddy. In cold weather heat the platinum bath to 70 degrees; in fact for the best of results at any time, the temperature of this bath should never be much below 70 degrees Fahr. Vigorous prints will stand vigorous toning in a strong platinum bath. Weaker prints require gentle or slower toning. Slow toning is often caused by not using the proper kind of phosphoric acid. Purchase phosphoric acid in small quantities (ask for 50% phosphoric acid), and keep bottle tightly corked. Slow toning is also very often caused by the water being very alkaline, as alkaline water will precipitate the platinum.
Washing Prints After Toning In Platinum Bath. As fast as the prints become toned transfer them to a tray of fresh water, and as you proceed with your toning occasionally separate the prints in the fresh water so that they do not become matted together, until all the prints are toned. After all the prints are toned, it is important that they receive a thorough washing before being placed in the fixing bath. The chemical action of the platinum bath must be acid, or it will not tone, therefore, the prints coming from it will naturally be in an acid state. For this reason, it is absolutely necessary to wash the acid out of the prints. If this is not done, acid will be carried into the hypo, producing sulphurization and yellow whites.
201. The prints should have at least three changes of water before fixing, and between each change must be thoroughly picked over and over, to insure against the possible chance of any of them sticking together, and to thoroughly eliminate all of the acid from the prints before they enter the hypo bath.