Elevating the humble cyanotype…with a UV-enlarger! 

I’ve been shooting black and white film for over 18 years, and since a few years ago, I have had my own darkroom set up in the basement. I love to do some uncomplicated printing on RC paper every now and then. When I built my own XPan-format panoramic camera, I was confronted with a problem. How do I print these negatives large enough for the photos to shine? Black and white paper in large sheets is very expensive, so I wanted to try something else. I had tried to do photoetching with an enlarger before, so when I saw a youtube movie on cyanotypes something in my mind clicked. I was going to build a UV lamp into my enlarger and print large cyanotypes onto watercolour paper!

This simple thought turned into a very long enjoyable process. I learned a lot and made my own custom UV enlarger. In this article, I will explain how I make cyanotype prints with it. If you are interested in the build process of the enlarger, consider watching this podcast on YouTube.

Cyanotypes, best known through blueprints and Anna Atkins’ botany

Sir John Herschel invented the cyanotype in 1842 as one of the first permanent photographic processes. It is based on iron salts and creates rich Prussian-blue prints that have an amazing tonal scale. Blueprints are cyanotypes and this is probably how you know them.

Cyanotypes were first used to make photograms. By placing plants on top of cyanotype paper and exposing it to sunlight botanist Anna Atkins catalogued plants in the 1850s. Blueprints are photograms from line drawings placed on top of cyanotype paper. The chemicals for classic cyanotypes are cheap, easy to handle and relatively safe. You don’t need to work in the dark as they are only sensitive to UV light and the process needs very long exposure times.

Enlarging cyanotypes – the basic process

If you have a UV enlarger, suddenly you are no longer dependent on the sun. You can print from negatives and enjoy more control over the final print. The process is similar to making a black and white print, but you have to coat the paper in advance, and development is simply a wash in water.

Preparing the cyanotype solution

Assuming you have a kit for classic cyanotypes, you combine equal volumes of solution A and B, and make sure you mix this well. The mixed chemicals should be used immediately and do not keep.

The moment they are mixed they are light sensitive. One sheet of A3 paper (30x42cm / 12×17 inch) takes about 5ml of solution. Because you need only small quantities it is helpful to use a pipette for each solution (Don’t share a single one across both, it will contaminate the stock solutions).

Choosing the right paper

Not all paper is suitable for making Cyanotypes. Watercolour papers are best, I use 300g/m2 weight paper because it handles development and drying better. If your prints have a grey rather than blue look your paper is likely too alkaline. A lot of archival papers are buffered and this can be a problem. For advanced users: Mike Ware’s new cyanotype formula is much more sensitive to paper buffering. Try a few paper types from your local art store to find a brand that works for you.

Coating the paper

Coating the paper is quite easy. Apply the solution to the paper with a glass rod or a brush. I use a cheap foam brush and it works quite well so far. Make sure you coat the paper lightly in a single layer. This is enough to reach deep dark blue tones and makes it easier to control highlights I feel.

The classic formulation doesn’t readily sink into the paper, it tends to lay on top. If this gives you trouble, you can add a drop of wetting agent. After coating, allow the paper to dry for about 1 hour.

Making test strips

Cyanotype is a very insensitive process. Exposures of 5-15 minutes in the sun for sunprints are not uncommon. With my UV enlarger, I enlarge 6×7 negatives up to 50x65cm (20×24 inch) in about 25-45 minutes depending on negative density — UV transmittance to be exact.

Because correct exposure can vary widely it makes sense to take an f-stop approach to test strips and try exposure sequences such as 10min – 14min – 20min – 28min – 40min – 56min. In this way, you can be fairly sure that you can find the correct exposure in one go, and given how long this takes it makes sense to be efficient! You can make cyanotypes under dim light without any problems. My enlarger is in my living room and I just watch a movie whilst printing.

When you look at the test print you see that a visible image is formed immediately without development. The dark shadows first become dark and then reverse to a light shiny grey. It seems that the print is heavily overexposed but only once this stage is reached do you have a correct exposure.

SAFETY: UV light can damage your eyes, make sure to wear protective eyewear!

Developing cyanotypes

Developing can be as easy as washing in water for 10-15 minutes. The unexposed solution washes out and the Prussian blue remains. You do lose a lot of the blue in the process. This is the reason why you need to overexpose the print.

Using an acidic wash prevents this but it also impacts contrast. More on this later on. After the wash, the print will still increase in darkness due to oxidation. To judge the test strip it is best to allow it to dry.

Alternatively, you can add some hydrogen peroxide to the last wash, in that way you reach the maximum density almost immediately and you can judge the exposure time right after the wash.

Making the final print

Making the final print doesn’t differ much from making a test strip. The difference is that you want to position your paper more precisely. You cannot use a red filter for UV enlarging as you would use for black and white printing, moreover, UV light isn’t visible to begin with. To solve this I use copier paper on the baseboard because the whiteners in the paper fluoresce blue under UV light. Also, you can simply position the cyanotype paper on the easel with the enlarger turned on. The few seconds it takes to position the print do not impact a 30-minute exposure.

SAFETY: UV light can damage your eyes, make sure to wear protective eyewear!

Drying the prints

Watercolour paper is hard to keep flat during the drying process. I took a look at baryta paper methods and came up with my own variant of drying paper by fixing it to a pane of glass with gum tape.

I fix the wet paper to a metal whiteboard and use neodymium magnetic strips to keep the paper down. Overnight drying results in a flat piece of paper and because of the magnetic strips I don’t need to cut off any tape.

Contrast control in cyanotypes

I have alluded to this previously but there are actually two main formulas for Cyanotype. Classic, as formulated by Sir John Herschel and ‘new cyanotype’ invented by Mike Ware. These two formulations behave very differently. Please see the table below.

Classic cyanotype needs a high contrast negative. I had great success with printing studio-lit portraits on Rollei RPX 400 black and white film.

The new cyanotype formulation (see this Youtube video for a how-to) is very low contrast. It has a very long tonal scale and will look very flat with the average negative. In my experience this pairs really well with high contrast films. I personally use Rollei Retro 80s, a rebranded aerial observation film.

Classic Cyanotype versus New Cyanotype

SAFETY: New cyanotype CAN be formulated with dichromate. This is a carcinogenic substance. I strongly recommend you do NOT use this chemical, it is not worth the health risks!

SAFETY: Always add acid to water and never water to acid!

Creative Avenues

Cyanotype, with its roots in photogram use, really invites experimentation. The materials are cheap and you can make very large prints. Personally, I like exploring combinations of photos and photograms and selective coating of the solution on the paper to create collage effects.

~ Douwe