Attempt at duotoning a cyanotype with gum

Oh hum!  The theory was that I would take one of my cyanotype prints ( see Cyanotype - 28/12/2010 below) and, retaining the cyanotype blue in the shadows, colour the highlights with a purplish red.

So much for theory!  Despite pre-sizing the paper with a coating of uncoloured gum, and then using a very diluted pink and pale blue watercolour gum mix for the colour layer, I still have red staining across the whole image, shadows and highlights.

I suspect that my 'rose' watercolour pigment bites too well on the watercolour paper I am using and gets embedded in the paper during the washing phase.

Gum over Cyanotype

The basic technique is to coat the paper with a coloured gum arabic solution which has been sensitised with potassium dichromate solution.  Dichromates are not themselves sensitive to light but when mixed with some organic substances makes the mixture harden when exposed to ultra-violet light becoming nearly insoluble in water.  Emulsions made from gum arabic, potassium dichromate and colouring pigments can therefore be used to make a photographic positive from a negative by contact printing.

After exposure, the print is floated face-down in water to dissolve away the unhardened gum and wash out the unused dichromate from the paper.  What is left is the positive image exposed by the light.  This process is called by its traditional name of Gum Bichromate printing  (BIchromate was the historical name of what was later called DIchromate, but is now called Potassium Dichromate (VI) )

In this example, the cyanotype was produced from a negative, but the gum layer was exposed through a positive film, as I wanted to expose the highlights.  Ideally, the result should have been lilac/purplish tones through the highlight areas of the print.

Oh well - better luck next time!

In the darkroom - Lith printing

This is something I've wanted to try for a long while - I've had the kit for about 15 months and not got around to it until this week's college evening!

Lith printing is a printing technique in which an image is overexposed by about 2 stops onto a fibre-based photographic paper.  The resulting image is then developed in a special 'lith' developer, based on Hydroquinone in a very alkaline solution.  The development process is 'infectious' which means that development starts first in the shadow areas, and as these darker tones start to emerge they develop even faster - the process causes the dark areas to become coarse and grainy whilst the highlight areas have only just started development and remain soft and fine-grained.  The resulting lith print is hard in the shadows and soft in the highlights, exhibiting colour effects caused by the fine division of the grain particles in the paper, so that the highlights appear tinted in shades of yellow, orange and brown.

The key to contrast and colour in developing a lith print is deciding when to snatch the print from the developer and stop the development of the shadows.  When the print is lifted from the developer the shadows stop developing almost immediately as the developer soltution in the paper is exhausted very quickly.  the highlights continue to develop until the process is stopped in the acid bath.  This makes the duplication of a print very difficult as the precise moment of snatching and stopping the print can lead to quite significant differences in tonal range and density.

This is a print that was developed for about 5.5 minutes and snatched and stopped as soon as the picture looked recognisable under the safe light.

Too soft

The next try was between 5.5 and 6 minutes, also snatched and stopped immediately - see how explosive the development is  - when it finally starts!

Too hard

Finally, I managed to get the tonal range I was looking for, only to find that I'd contaminated the paper with fixer from my gloves.  That's what caused the featureless finger prints all over the bottom right of the frame...

Just right - but I've broken it!

Now I've managed to get viewable results, I'll be much more confident at the next try.  I'll try a range of exposure times and then try pulling the prints early and late to see what colour effects I can get.

A walk in the rain...

I finally got out with my Bronica and went for a short walk in the drizzle round Ridgegate Reservoir in Macclesfield Forest.

Loaded up with Fuji Neopan 400 Pro and carrying my trusty lightmeter I set about taking some shots of the surroundings - I need more negatives for my darkroom portfolio!

Raptors

Finally - a day off.

I went over to Gigrin Farm Kite Feeding Centre to see the Red Kites being fed.  An amazing experience - 70 or 80 birds stooping to pick up chunks of beef for their lunch!

I got a few shots which were in focus, not blurred and big enough to crop - but looking round at the other guys lenses I felt a bit under-endowed!

This one got his prize.  The birds mostly don't land, but grab the meat en passant and fly off with it, eating on the wing.

Truly beautiful birds!

Happy New Year!  

May 2011 be all you want it to be...