Cyanotype

One of the first photographic processes to use a negative was the cyanotype (also called sun-prints).

The cyanotype uses an iron-based chemistry in which a mixture of ammonium ferric citrate and potassium ferricyanide dissolved in water is used as the sensitiser.

The solution is painted onto pre-shrunk watercolour paper and dried in the dark - producing a pale yellow coating on the paper.  The paper is then placed in contact with a negative and sandwiched in a printing frame with a clear glass window.  The paper is then exposed to ultraviolet light for several minutes until the coating 'bronzes'.  When the paper is washed in cold running water, the exposed areas are rendered blue (by the Prussian blue pigment produced by the action of the light on the sensitiser).

For this process, I again used the ChartThrob (http://www.botzilla.com/blog/archives/000544.html) program to calibrate the negative.  The next step with this image is to attempt to put two layers of gum over the image to duotone the highlights and shadows.  More later (when it works???)

What me? Worry...

For a person who loves technology - I'm curiously reticent about self-publication.
If it weren't for this photography course I would still not have a web-presence at all!

Well - fear and trepidation aside - here's some of what I'm trying to do.

I am going to put together a portfolio of silver prints using the traditional darkroom skills.  I'm not yet a master printer - but I want to become much better.

I thought I would start off by producing a couple of contact prints from digital negatives.  The process is fairly simple: first, render a digital photograph as a monochrome image, invert it to a negative and flip it horizontally.  The resulting image is then printed onto an OHP transparency acetate using the ink-jet printer.  When completely dry, the resulting actetate negative is contact-printed onto your choice of photographic paper, in the darkroom.  The first image is an example of a finished print using this process.

As you can see, the image printed at grade 2 is lacking contrast, although the midtones are good and the sky detail has held well.  I used a program called ChartThrob (http://www.botzilla.com/blog/archives/000544.html) to calibrate a Photoshop curve which is applied to the image prior to inverting it.  The resulting image is below:

Now the image (still printed at grade 2) has a much greater contrast and the sand and sky highlight details are much better preserved.

I will use this program again to calibrate the process for cyanotype and gum prints...  later.