Re: Vandyke Question
My only "expertise" in VDB is from mixing it in my own studio & observing all those space cadet undergrads have at it... The only failures we experienced were easily diagnosed: in one case a metal cover on one jar of solution (whichever it was) was an obvious contaminant, in the other (as noted) the supposedly distilled water (sealed in an "official" distilled label) turned out to be regular tap water. But beyond that we stirred fast or slow, & probably committed a dozen other breaches without trouble, tho come to think of it I got a call from the department last semester about some VDB trouble (which I think was ultimately traced to contaminated silver jar, but I'll see if I can check back on that).
But, given the far better care you have obviously exercised, my guess would be that there's another factor at work, that for instance one of your chemicals could be below par. Have you made the emulsion from these chemicals successfully, or with less hassle, in the past?
Which, if any, is new? My own experience with other emulsions is that ferric ammonium citrate can arrive bad or turn bad (I recently had to throw out half a pound that turned into cement, tho granted it was ancient). Is the silver nitrate white white & quite crystal? Tartaric acid I can't comment on since we worked off the same jar forever. And I assume of course that given your general meticulosity your beakers and stirrers are clean...
My only other comment at this point is that I, too, have used VDB emulsion more than a year old without a problem. The inside of the jar seems to plate with silver fairly soon, without any noticeable effect on the print, and old emulsion will have black specks which reabsorb as soon as the solution is smoothed on the paper.
On Sat, 23 Feb 2008, Scott Wainer wrote: