Vandyke, does the solution age further...

I did another print session with the same Vandyke solution I made a few weeks ago, and I had much, much better Dmax. I was not complaining before, but here I get very deep brown while before I had medium/dark brown as deepest shade.
The thing is, I now use a very controlled method of printing (including hygrometry), I haven't changed a single thing.. so the only thing I can think of is that the solution "ages" further than the "24 hours" period... As a matter of fact, there is a small deposit at the bottom of the bottle that wasn't there before, so maybe residual metal solidified, and makes the solution more balanced ?

Any experience or ideas ?

A scan :

Vandyke solution is a very active compound. If you made the solution fresh and used Green Scale Ferric Ammonium Citrate, I wouldn't be surprised if you noticed it changing over a few days.

We only use Brown Scale FAC in our Vandyke solution at Bostick & Sullivan because it has a considerably longer shelf-life before the silver crashes out of solution. Solutions made with green FAC often require additional heating and the addition of more Tartaric Acid to re-dissolve the silver dregs that form at the bottom of the bottle.

I have a bottle of VDB solution that is about 2 years old and it has a slight mirror finish coating the inside of the bottle, but the solution still makes a decent looking print.

Another advantage of using the brown FAC is the final images aren't as overly contrasty. The mid-tones have better separation, and the highlights aren't blown out like when you use green FAC. Negatives that print in platinum/palladium well seem to like the brown FAC version better, in my opinion.

It has always seemed to me that the solution becomes much better with age. Both d-max and contrast improve. I usually try to mix a batch at least 3 months before I plan to use it. I've used solutions of the standard formula made with green FAC after two years with fine results. Silver does precipitate as the solution ages so decanting and filtering a bit to work with now and then from the stock solution may prevent problems with coating specks.

Joe

I'm curious, is was the sensitizer double-coated for this print? And what do you do in the way of humidity control?

@Dana:
Yes I had the problem with the precipitate, solved by adding more tartaric acid to it (I think that trick was a Sullivan answer lost in the mailing list archive too, thanks again); but I let it decant and I think I will leave the silver at the bottom without filtering. Interesting point about the contrast, the "traditional" vandyke with green seems to make quite busy shadows, but this might be the double coating ? Do you double coat with brown too ?

@Joe:
Thank you for that info, it seems to confirm my own observation that the solution does evolve quite a bit, way pas the traditional timeframe that is mentioned about in the papers/articles I've read.
I've been wondering if I just should make a new batch already, and add it to the existing bottle.. use it as a "seed"!

@Jordan:
Yes this is double coated. To control the hygrometry I use a small room (my bathroom) with a hygrometer and I ventilate and/or mist it until I reach 65%, it's fairly easy to do in practice, and it keeps stable for quite some time once reached...
I use that room to do the coating and drying. I coat one sheet at a time, and dry it using a hairdryer for a very specific time, then expose it immediately. I let the paper stand flat one minute between coats.

Of course it's not very productive, since I cannot pre-coat and batch dry the paper; I can do one large, or 2 smaller (A6) print at a time only. But I get the results I want, so it's worth the trouble.

buze said:

Yes this is double coated. To control the hygrometry I use a small room (my bathroom) with a hygrometer and I ventilate and/or mist it until I reach 65%, it's fairly easy to do in practice, and it keeps stable for quite some time once reached...
I use that room to do the coating and drying. I coat one sheet at a time, and dry it using a hairdryer for a very specific time, then expose it immediately. I let the paper stand flat one minute between coats.

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I personally have never observed a significant change in results with VDB solutions during the first few weeks after they were mixed. Over a period of several months it is typical for the silver to coat the inside of the bottle, but this also does not change much the printing qualities of the solution, though if left for several years it certainly will in time.

In general it is good to expose the coated paper as soon as possible as this will give you good Dmax. However, coated paper underdoes a considerable change in printing characteristics as it dries. I suggest that you allow the paper to dry about about 15 minutes at 65% RH to stabilize it and and I think you will get more consistent results. Thirty minutes might even be better. I think it much more likely that the variations you are observing are due to to the method of drying than to changes in the VDB solution.

Sandy King