Description
Single-bath blue toner for silver gelatin prints and alternative processes such as Kallitype, Vandyke, salt print, Athenatype, Lobotype and Argyrotype.
Kit for 6-10 litres toner solution
The image tone depends on the paper used, but can be adjusted from light to dark blue, as well as between green and magenta blue.
The kit contains five solutions to prepare the toner, of which at least three must be used. By varying the mixing ratios of the three main substances and adding the two optional solutions, finely graded shades of blue are possible.
Berlin blue is sensitive to alkali. Long rinsing times after toning should be avoided. To quickly remove the yellow colouration caused by the ferrizyanide, a decolouriser concentrate (dilution 1+9) is supplied.
As soon as the image whites are cleared, only water for about three minutes.
If the (greenish)-blue tone is to be shifted more towards violet or blue-grey, a weak alkali bath is used. A 5% alkaline solution is included in the kit, five to ten millilitres to one litre of water are needed for the the treatment. The rest can be used to remove toner residues from the tray after toning.
With the known toner formulations, as the toner is progressively used up, the undesirable Turnbull blue often develops very quickly in addition to the desired Berlin blue. This dye is not only deposited on the tray walls, it also stains the gelatine and the paper felt a blotchy blue. The MT7 kit contains a stabiliser that binds the Turnbull blue when it occurs during heavy use or long periods in the open tray.
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