The lumen print, like the photogram, typically results in a negative image, which can work well for abstract subjects, but is relatively limiting, as we often prefer to see recognisable scenes as positive images. This is normally overcome by either using large format negatives, or enlarged negatives printed on inkjet transparencies placed in contact with the paper as demonstrated in a previous video.
The positive lumen process however, allows us to make positive prints from in-camera exposures, enlargements from slide film, or enlarged prints made in the darkroom – it is a positive to positive process. The advantage with working directly from slide film or from enlargements is that we can now make our final print any size we want within the limitations of our darkroom setup. Also, the ability to produce a lumen print from an in-camera exposure means that we can make unique, one-off prints that are not only positive, but can be rendered in an array of colours depending on how they are exposed to light during the final stages.
Although my interest or speciality is in producing one-of-a-kind photographs, another novel aspect of the positive lumen process is that we are left with images that appear from a blank sheet of paper, as in this video. There are many exciting possibilities associated with this characteristic, for example one could mount an exhibition that appears before the eyes of the viewers and changes over time. We could also send seemingly blank pieces of paper to our friends and family, only to surprise them with the magic of an appearing image.
A final advantage of the process is that the resulting images do not need to be fixed, although they can be if so desired, for the purposes of toning.
The steps are as follows:
- expose and develop your paper in order to produce a negative
- thoroughly wash the paper to avoid contamination
- bleach away the image which should take about 1 minute to complete
- wash again
- place the paper the clearing bath to remove the staining, agitating periodically, again for around 1 minute
- wash the paper again
- dry (optional, best carried out in the dark)
- Bring the paper into the light in order for it to “develop” into a visible positive
Just as normal lumen prints give different colours according to the type and intensity of the light they are exposed to, so do positive lumen prints. Slow development under artificial lighting will produce different tones than rapid development in strong UV light. Experiment using different durations and intensities, and mixing and matching the two. Colour (RA4) paper can also be used for further options and effects, and the process can even be carried out on film.
Fixed and selenium-toned prints have turned out to be a very neutral grey, compared to a normal, untoned print made on Ilford MGIV RC, which is what I am using here. Unfixed prints have tended to give very warm tones from a pleasing chocolate brown to a very garish bright orange.
The recipe I use is based on the formula for reversal processing of black and white film:
The bleach is composed of two parts, A and B –
Part A = 14g of SODIUM BISULFATE mixed in 500ml of water at 20 degrees Celsius
Part B = 1g of POTASSIUM PERMANGANATE mixed in 500ml water
Mix both parts together before use.
(This gives 1L of bleach with is plenty, so if your scales allow it I suggest mixing up half the quantity unless you need more for processing larger prints for example.)
The clearing solution is made from 25g of SODIUM METABISULFITE or POTASSIUM METABISULFITE, (depending on what is easiest for you to get) mixed in 1L of water.
As with all darkroom work be sure to take the right precautions when working with chemicals, using gloves and goggles to mix up the bleach and clear solution. Proper ventilation is a must, especially for the clearing bath. Pour it back into its storage bottle after each use to avoid it sitting in an open tray.
Make sure not to confuse your metabisulFATE with your metabisulFITE.