Puzzling paper problem – A carbon transfer print surface anomaly

There has been this tiny problem bugging me for a couple of months. It popped up when I moved to DAS sensitized tissue for my carbon transfer prints. Some sort of micro-scale unevenness in tone. It reminded me a little bit of some form of reticulation – but not quite. But I think I’ve cracked this nut now, and it’s actually much more obvious and benign than I had imagined it to be.

Yesterday I was doing a demonstration of carbon transfer printing. Since it’s impossible to cram the entire process from start to finish into a few hours, I had prepared (TV-chef style) some partial products in advance. As a consequence, I ended up with a few identical prints, and this turned out to be the key to solving the mystery. Here’s the image I was working with for the demonstration:

4×5″ carbon transfer from Fomapan 400 negative. The irregular lighting (e.g. the band on the left) is a scanning artefact. Image tone in reality is nearly dead-neutral grey.

After reorganizing my workspace, one of the things I was left with this morning was this pair of identically made prints from the demo yesterday:

Near-identical prints: double transfer and soaked in water on top, double transfer before final water soak (still ferrotyped) at the bottom.

These are double transfer prints, so they were initially developed onto plastic transparency temporary supports, and from there, transferred to gelatin-sized paper. I use Schut Laurier paper for nearly all my carbon prints at this point because I like its subtle surface grain/texture and neutral/bright whites.

After the double transfer and drying the final support paper in contact with the temporary support, the paper with the image on it peels off the temporary support with ease. What is left, is a ferrotyped print whose surface has formed to the smooth surface of the temporary support. Since this is a nearly perfectly smooth surface, the print surface (i.e. the gelatin image and the gelatin paper sizing) ends up nearly perfectly smooth as well, and super glossy:

Ferrotyped surface of a double transfer print as it comes out after releasing from the temporary support. Note the high-gloss look.

I sometimes leave the prints like this. Especially test prints, I don’t bother processing any further and they remain in this weird, quasi high-tech, high-gloss look. But usually, I prefer to finish the prints by giving them a final soak in cold water and then let dry naturally. The then end up with a more subtle eggshell sheen, which is one of the things I really like about these prints:

An identical print after soaking it in water. After drying, the high gloss makes way for a more natural eggshell sheen.

Back to the little problem I had been seeing. It’s not visible in the photos above – we need to zoom in quite a bit to make it visible. Here’s part of an 800-dpi scan of the ferrotyped (high gloss) print:

Enlarged section of ferrotyped print. Note the tiny swirly lines in the even grey area.

The phenomenon I’ve been running into consists of these tiny swirly lines. They are too small to individually make out with the naked eye, but easily visible with a powerful loupe. When viewed without aid, areas that should be evenly toned, tend to take on a kind of slightly coarse, gritty look because of this effect.

Since the image above is somewhat subtle, I’ve boosted the contrast in the version below to emphasize it:

Same section with contrast boosted to emphasize the granular effect

I was suspecting all kinds of possible causes, ranging from an adhesion problem in the double transfer process, to some kind of pigment clumping, a reticulation effect, something weird with the DAS sensitizer (I had never seen this on my dichromate prints) – but none of these explanations made much sense to me. That is to say, I could never work out a mechanism that would fit how the effect actually looked. In fact, I wasn’t really sure what in the heck I was looking at in the first place. I just couldn’t put my finger on it!

What did strike me this morning, and this had somehow evaded me for the longest time: the anomaly is not present on the otherwise identical print that I had given a soak after it came out ferrotyped. In this print, the areas of even tone are indeed perfectly smooth and even. I tried to make a scan of this, but the strip light of the scanner does funny things with the surface texture of the print, emphasizing the fibrous texture of this (gelatin sized) paper:

Scan of roughly the same area on the print that was given a final soak; the one with the natural eggshell finish. The scanner does funny things with the surface texture, reflecting light off of the fibrous texture. In reality, when viewed up close, this print is very nicely smooth in tone.

So the example of the soaked print above isn’t representative of how it looks in reality. In reality, it has perfectly smooth tonality and it is free of the odd granular effect the unsoaked print exhibits.

But…is it? Because in fact, the unrepresentative scan above does hold a very obvious clue: the fibrous paper texture! This morning, when studying the ferrotyped version, it struck me that one thing seemed to be consistent with the pattern: paper fibers! What appears to be happening, is that during the transfer process when the final support and temporary support are sandwiched together, some of the paper fibers near the surface of the final support poke more or less through the gelatin sizing, making it to the very print surface. There, they remain embedded underneath the thinnest gelatin layer of the image itself. This also explains why the defect is virtually invisible in very high-density areas: here, the fibers are hidden below a heavy layer of pigment. But in lower-density (grey) areas, the fibers sort of shine through the image layer.

Apparently, as the print is soaked a final time, the gelatin of the image and the sizing layer redistributes itself a bit over the paper surface, resulting in a more even thickness over the paper fibers. This makes the actual paper texture more visible, since the gelatin layer basically follows the surface roughness of the paper. From a distance, this is what creates the eggshell finish that I like so much. At the same time, it also ensures that the optical density ends up more even and in line with the actual image/pigment density.

So I think this mystery is solved. It’s just an artefact of the sizing interacting with the material properties of this particular paper. No doubt the effect will be different and perhaps even absent on other papers, depending on their surface characteristics. Since virtually all of my transfers have been to this particular paper, I simply had not spotted the influence of the paper used on this effect. Ultimately, I consider the ‘problem’ as harmless, since I intend to always give ‘keeper’ prints a final soak, because I prefer the eggshell finish it gives anyway.

It’s funny how sometimes the simples things remain a puzzle for so long. I can’t get over it for how long I just couldn’t put my finger on it!

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