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Processing for permanence 

PROTECTIVE COATINGS : Even when the last traces of silver and hypo are removed from the print the silver image is libel to be attacked by various substances in the atmosphere. There are various toners that can be used to chemically alter the silver to more resistant metallic compounds. Selenium and gold are considered the best in respect to this.

Not only will they chemically alter the silver to make it less susceptible to attack, they can be mixed in a manner that either changes the tone of the print little or a great deal. The amount of this colour change through the use of toners is dependent upon a whole range of factors and among these is the type of paper, developer, temp and time of development, dilution of the toner etc.

However before we look at toning it is important to remember that poor fixing and washing will show up through the toning.

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