Silber POP Lobotype

Description

The combination of ammonium iron(III) oxalate and silver nitrate for a printing out process is obvious, even if the mixture of the two solutions does not look promising at first glance. However, this was one of the reasons why I considered initial attempts to have failed about 20 years ago. It is quite likely that other printers have already looked into this possibility. I would like to point out that I do not want to give the impression that I have found something completely new. The term lobotype merely serves to distinguish it from related processes such as Vandyke, Argyrotype, Kallitype and Athenatype.

At least two solutions are mixed, ammonium iron(III) oxalate in a concentration of 40 - 45% and silver nitrate in concentrations between 10 - 15%. A higher concentration than 10% is not necessary, but can be used to increase contrast and maximum blackening.

As with other alternative processes, Tween can be added dropwise to facilitate uniform application, but this is not absolutely necessary.

Adding a few drops of concentrated citric acid can be beneficial to facilitate clarification and shift the image tone to a slightly cooler shade.

When mixing ammonium iron(III) oxalate and silver nitrate, the result is not a clear homogeneous solution, but a milky emulsion with a tendency to segregate again quite quickly. If a larger quantity is prepared for coating several sheets, the preparation beaker should be swirled slightly before taking a partial quantity each time.

Example of preparation with 12.5% silver for a slightly higher contrast and citric acid for a cooler colour.

For an area of 20x25cm 2 ml of emulsion are needed.

The application can be done with a foam or hair brush. A dry hair brush (Hake Brush) is absolutely necessary for an even, streak-free application.

Developer bath: Demineralised water or tap water acidified with a few drops of 50% citric acid.

Clearing bath: Citric acid 1%

Fixer bath: ATS Fixer acid 1+10

Some of the developers for the Kallitype can also be used. However, a clear change in the image tone could only be observed in a few cases. In any case, these developers should be used more diluted.

Tested so far are:

Sodium citrate 10%

Potassium citrate 1,5%

Ammonium citrate 5 %

Sodium acetate 2%

Rochelle salt for Kallitype 1+1 dilluted

Potassium oxalate and phosphates are unsuitable.

Recommended toners:

MT10 Gold toner before and after fixing

Platinum and Palladium toners before fixing

MT7 Iron Blue Toner after fixing

MT3 Vario Toner after fixing

Detailed instructions are enclosed with every order.

For the creation of digital print negatives, a special curve is required, which can be supplied free of charge on request.