Wednesday, December 31, 2014

A lab note on Kodak Medalist paper, single weight

Privitera-Wilson, untitled, 2014

Rich Turnbull and I hosted a chemigram workshop at the International Center of Photography recently - nothing new about this, we do it a couple of times a year.  But this time, instead of having students gain the theoretically valuable experience of coating their papers with varnish, we decided to forgo the unpleasant odors associated with that task and instead provided them with pre-coated papers.  A sensible idea, right?

So we looked in our storage locker for papers and pulled out a ream of Adorama RC, 5x7" and a box of Ilford FB, 16x20", which we cut to size.  On the shelf below lay a variety of vintage papers, Velox, Portriga, and the rest.  My hand hesitated, then reached for a pack of Kodak Medalist.  It was unopened, expiration date 1965.  I said why not give some to the students, heck we hadn't had a chance to try it out ourselves, this'll be a good test.  I coated 6 sheets with Golden MSA varnish and shuffled them in with the other 40 or 50.  We headed up to 43rd Street.

That afternoon we came to the part of our workshop where we need the coated papers.  Everyone was instructed to grab a bunch, incise them, and toss them into the tanks of fixer and developer.  On the backs of the paper we'd written what each was, but no one really cared.  Chemigram workshops seem to generate a mist of intoxication that is quite separate from the chemistry used; the students were giddy or serious, chatty or thoughtful, but their eyes were glued on the inexorable changes in the way the front of the paper looked, not the back.

In this type of chemigram process we can speak of the paper reaching a mature phase when the resist on the paper starts to weaken its grip and lift off ever so slightly at the edges.  This could take 15 minutes, it could take 30 or more.  It's at this point, whenever it comes, that the artist must respond quickly to a rapidly deteriorating environment on the paper or lose control entirely.

Among the first papers to reach maturity that afternoon was one by Paulette Privitera-Wilson, seen above.  She controlled it and brought it home in a splendid way.  Others did too, among the early papers to mature.  Rich and I looked at each other and said something's going on here.  They're all deep red, magenta, deep orange, rich purple - and they're all Medalist!  On most papers the chemigramist has to work to get these colors, really work, and often they don't come easily.  But here every beginner in the class was getting them.  We agreed we'd meet later at MGC to talk this over.

Medalist single weight (SW), surface F
The first thing we had to do was confirm this finding.  That night we coated Medalist single weight (SW) papers as well as double weight (DW), using various brush-on and spray varnishes: Liquitex Soluvar, Golden MSA, Krylon Clear Acrylic, Rustoleum Acylic.  As soon as they were dry we performed random chemigram maneuvers on them and brought them through the trays to completion.  Here are some that Rich gave me.

Medalist SW, Liquitex Soluvar

Medalist SW, Liquitex Soluvar

And one of my own using Krylon:

Medalist SW, Krylon Acrylic Spray
On the other hand, when it came to double weight the performance was more mediocre - although we did notice a faster response compared to contemporary Ilford or Adorama, both fiber and RC (not shown).  Here's Rich again, this time with Rustoleum on DW:

Medalist DW, Rustoleum Acrylic Spray

Another observation, a footnote, is that in attempting to make etched chemigrams with Medalist SW we found that the bleach part of the process works fine but the etch part not so much - in fact quite poorly.  The veils vanished before they had a chance to appear.  This may be due to the thinness of the paper but more likely to the thinness of the emulsion itself.  An interesting experiment might involve fattening the emulsion layer with an overcoat of liquid emulsion, such as Rockland Colloid's Liquid Light.  We assign this as homework.

Medalist SW chemigrammed
Medalist SW as etched chemigram

Overall then, what's going on here?  Clearly the thinness of the SW papers made diffusion that much easier, at least through the back of the paper; we don't think the G surface of the DW, lustre, had anything to do with it.  So the attack on the SW was more aggressive and faster, but what about the colors?  Something in the DW was getting filtered out or was being degraded, and that same something wasn't even present in the modern papers.  We decided to turn to the George Eastman House museum of photography in Rochester NY for help.

Nick Brandreth pointed us toward cadmium.  Aha.  That friend of painters for two hundred years and counting, that bringer of life to reds, yellows, and oranges.  Cadmium since the 1950s had been formulated into several photographic emulsions, particularly the chlorobromide or warm-toned ones, for its ability to sharpen tonalities through its anti-foggant properties: it made low-level distinctions sharper.  The side effect was the brilliant pigmentizing of the emulsion, but this would have escaped the notice of conventional black-and-white photographers and would have to await the rise of chemigramists in the new century.  Meanwhile in portraits, the market Medalist was mainly created for, it produced excellent results.  Yet as public awareness grew of the toxicity of materials like cadmium, which doesn't degrade in the environment but keeps accumulating, pressure grew on Kodak to reformulate its emulsions, and it finally did so in the 1970s, selectively, at a precise date unknown to us.  But we do know, from testimonies of photographers from the period, that Medalist was never the same after.

The form of cadmium that was used in emulsions may have been mainly cadmium sulfide or cadmium selenide and in hindsight the quantities were negligible, though very significant and helpful to a chemigramist.  Should we sound the health alarm?  Probably not.  By far the greatest part of our cadmium intake comes from the food we eat and the air we breathe, from soils, plants, aerosols spewed up by volcanoes, and so forth, and not from handling Medalist.  A good summary is found in a 2010 article at Environ Health Perspect. Dec 2010; 118(12): A528–A534.  

And not all emulsions had their cadmium stripped out at the same time, not even at Kodak.  I've been told that Ektalure's emulsion contained cadmium until the mid 1980s.  Perhaps a reader can confirm this.  It would not surprise me to hear of a photo paper made somewhere in the world that still employs cadmium.  I'm a buyer if you can find it for me.

The next workshops in New York are scheduled for February 28 at Manhattan Graphics (Turnbull), March 28 at ICP (Collins/Turnbull) and five Sunday classes at JCC Manhattan (Eva Nikolova), April 19 - May 17.