Lumens – Dmax?

I’ve been playing with lumen printing for a couple of years now, and have often wondered if there is a way to increase the dmax so as I could get darker darks in the image. A few times I’ve tried painting different chemicals onto bits of photo paper and exposing them to see what happens, generally without much success, table salt makes for a cooler colour, but only a slight increase in the dmax, ammonia creates an unreliable and slight dmax increase, with cooler colours and so on.

This sort of thing – from memory the bottom center was dipped in a table salt solution – which only partially reacted causing the cooler grey bits at the edges – the bottom right was dipped in ammonia (cleaning product grade). So generally I haven’t seen much of a result. (All of the photo’s in this post have been fixed, washed and dried.)

So the other day with nothing much better to do I tried out the chemistry I had at hand, mainly testing a paper (velox – above and below) rather than the chemistry itself – I also had selenium at hand, so I painted “Se” on a piece with a brush dipped in it and put them out in the sun. This gives a bit more of a reaction, but still slight in general. The chemicals I did this with were cleaning grade cloudy ammonia, Potassium dichromate at approx %5, KRST Selenium toner, and household bleach (something hypochlorite?)

And it would seem that the selenium responds to this – rather intensely! The other 3 reacted immediately, mainly cos of the water, but over 2-3 hours they levelled out again as the water evaporated – the bleach reduced dmax substantially (which is in itself pretty interesting). But the selenium reacted far far slower than the others and kept gaining density long after the others had hit their dmax. The others showed a couple of spots of reaction, but really, the image above speaks for itself.

So I figured that one of three things was happening – the first possibility being that the thiosulphate in the KRST was grabbing the silver and converting it to something that was still light sensitive, this didn’t make sense really, but was possible – The second was as above but the selenium was converting this secondary substance into something else – this was, and still is a reasonable assumption – the third option was that the hypochlorite wasn’t doing anything positive and it was purely a reaction between silver halides, selenium salts, and the sun, thus forming silver selenide by oxidation (there might be other options – but I’m no chemist, and even less of a physicist).

So my next step was to coat some sheets of RC photo paper with selenium in different ways – I did the following;

Soaked a sheet of paper in strong 1;3 selenium and let it drip dry (these had no subsequent light reaction).

Soaked a sheet of paper in weak 1;30 selenium and let it drip dry (these had no subsequent light reaction).

Soaked a sheet of paper in strong 1;3 selenium (these had no subsequent light reaction).

Soaked a sheet of paper in weak 1;30 selenium (these had no subsequent light reaction).

This proves well enough that the fix in KRST actually acts as fix, and thus the light sensitive halides were eliminated into the krst solution.

I also painted fix onto a couple of bits and let it dry in place, thus ensuring that the dissolved halides stayed on the papers surface – this was subsequently completely insensitive to light – which proves fairly safely that fix not only removes silver, but forms a compound which is insensitive to light, which eliminated any chance that the fix was acting as the agent (alone anyhow).

Lastly (well, first actually, but I’m getting the total failures out of the way first) I painted a liberal amount of 1;3 KRST onto another couple of sheets and allowed them to dry, these were the only successes – A sheet that was exposed to the sun went a dark grey/black which remained after fixing.

I then put a sheet into a contact printer with a waxed paper neg and exposed that to blue sky through a window, but not to direct sunlight, the result of 3 hr’s printing looked like this;

Not pretty by any stretch, but still extremely interesting – For an obvious start I should have used a regular neg, or exposed it to direct sunlight for the extra push – I can still get an idea from this, so that’s ok. The places where the solution pooled turned out bleached, which tells me that I was far too heavy handed with the selenium – this is reinforced by the fact that the places where I barely touched have achieved nearly full density, and the places i painted heavily are bleached back (pale). Looking closely at the border is interesting too;

This shows the range, from the very nearly black section where I just whisked the brush over the surface, through the faded area’s where I painted more heavily, to the fully bleached parts where the solution pooled – it would seem that the key to getting full darks is to only apply a very light coating of selenium.

This is reinforced by looking at the other side of the print, the brush marks there were so light that i didn’t spot them as I was coating the paper.

All in all a pretty interesting experiment – probably amongst the ugliest stuff I’ve posted here 😀 but I have a feeling that this has some very real potential if i tweak it a bit… Ok, a lot 😛 but I’m seeing something here that I haven’t seen before, it’s definitely worth looking closer.

For my next step I’m going to coat some fiber based paper very lightly with Se (1:3 and 1:30) and let it dry in darkness, then I’ll expose it in full sun under a proper negative – the fiber paper is cos the RC is waterproof and thus both repelled the solution, and refused to dry evenly – Plus I have an inkling that a nice print might turn up soon – I also need to try selenium toning after fixing as well (as opposed to selenium sensitising pre-exposure).


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