Silver plating
Empty bottle, which contained for some months a VDB solution. Inner walls are completely covered by a silver layer, phenomenon that goes by the name of silver plating.

There’s no solution on how to avoid them, if it’s better filtering the solution or collecting the clearer solution near the surface and leaving the other part where it is or again shaking the bottle before using. There’s no match exactly because the ammonium ferric citrate is different for every printer. Sometime shaking augments print dmax, but also add an unpleasant grain; filtering can augment and decrease print contrast, change tones; etc, etc… In general some attempts are necessary to determine which one is the most convenient procedure. Once determined the method, it is easy to keep a constant standard.

In every case this kind of precipitate, with prudence, has a poor impact on print and do not cause a large lost of salts.

The precipitate we’re talking about has nothing in common even with the white suspension obtained when C is added too quickly in A+B solution. If you energetically mix the obtained solution, this suspension goes easily back in solution. If you did add too quickly the C solution, a completely insoluble gritty settlement takes form.

In every case I always added C in A+B solutions with a lab agitator and a burette regulated for about a drop every second.

Remedy for precipitate inside VDB solutions

Augmenting the concentration of the tartaric acid inside B solution helps avoiding this settlement.

Tartaric acid can also be added in a classical solution that already contains the settlement; in fact, mixing the settlement gives the solution back.

The first time I made this attempt, I added 0.5g of tartaric acid inside the classical solution with the settlement until it completely disappeared. Adding 2.5g of tartaric acid, the settlement disappeared, but the solution had an opaque and absolutely not transparent aspect. Adding some more tartaric acid didn’t turn it transparent; therefore I imagine that this suspension is a different from the original one. Once it is at rest at the bottom of the bottle, a fine and dark powder settle in small quantities that can be easily filtered. Either the solution can be shook before using; in both cases the result is a correct print, without streaks or grains.

This experience brought me to modify the classical VDB solution to focus on the one I identify as VDB2, which is a solution with 4g of tartaric acid instead of the classical 1.5g.

VDB2 characteristics

The obtained solution is more contrasted and it has a higher dmax compared to the classical one. Its hue seems the same, even if this one is controlled by some other variables such as the paper humidity.

A big difference is that there’s no more printing out, but paper develops during the first washing. When the exposition is visually controlled, this can modify your own habits, to the detriment of a strong overexposure, but it is still easy to determine the correct exposition after some test prints.

Conclusions

The usage of VDB2 formula, in my case and with my ammonium ferric citrate, allows deeper and more contrasted prints than those obtained with VDB classical formula. The image is anyway similar to the one obtained with Wynn White’s VDB solution, but the huge advantage is that you can use the entire solution and not only the 50%. It is a considerable economical benefit.

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