One bath blue toner for fibre base and RC papers
In a kit to make 6-10 litres of working solution
The image tone depends on the paper you use. It can be adjusted from bright blue to dark blue and between green-blue and magenta-blue.
The kit contains five solutions for the preparation of the toner. You have to use at least three. By altering the ratios of the three main ingredients and by adding the other two optional solutions, you can finely adjust the blue tone.
Berlin-blue dye is sensitive to alkali. After toning avoid prolonged rinsing. To quickly remove the yellow cast of the ferricyanide, an acidic de-yellowing concentrate is included in delivery (dilute to 1+9).
As soon as the image whites are cleared, rinse the print for only another 3 minutes.
If you want to shift the blue tone towards violet or blue-grey, you can re-treat the print in a weak alkali solution. There is a 10% alkaline solution included in the kit. You need between 5 and 10ml per litre of water for this process. When you are done, you can use this solution to get rid of residue of the toner in the dishes.
Regardless of which one of the familiar toner recipes you use, progressive use of the working solution frequently generates the formation of an unwanted turnbull blue dye apart from the wanted berlin-blue. This dye not only accumulates on the inner walls of the dishes, it also stains paper-base and gelatine. You can combat this evil. The MT7 kit contains a stabilizer that binds the dye if it arises. This is usually the case after heavy usage or if the working solution is left in an open dish for long hours.