I thought I would write about an alternative photographic process known as ‘cyanotype’. The process takes its name from the characteristic blue colour of the monochrome images it creates.
The process is historically important as it was the first to use a negative to create a positive printed image. It was popularised in the 1840s by Sir John Herschel, the son William Herschel who discovered the planet Uranus in 1781.
Cyanotype is sometimes referred to as sun or solar photography. The reason for that being that the image is created by exposure to sunlight.
So what is the process, and can you create cyanotypes yourself? Well, the process is fairly simple and yes, you can produce your own cyanotypes.
Standard Photographic Process
Let’s just think about the modern process first. In modern monochrome film photography, an emulsion which is sensitive to light (using chemistry based on solver) is coated onto a plastic substrate (the film). The film is put in a camera and an image is focused onto the film and it is then exposed to light, typically for a fraction of a second. The film is then processed in various chemicals so that the ‘latent’ image on the film is turned into an image that you can see. This image is a negative in that light areas seem dark and dark areas are light.
To create a positive printed image, the image is projected onto photosensitive paper for a while. The paper is then processed in various chemicals to develop and fix the image. After washing and drying you have a printed photograph.
Modern films are light sensitive with an ISO generally in the 100 to 400 range. The chemistry of the film emulsion and the photosensitive paper is generally based around silver.
Cyanotype Process
In this section I’m going to discuss the cyanotype process. The steps are:
- Buy or make cyanotype paper
- Create digital negative (if needed)
- Place negative on treated paper and put in some sort of frame
- Expose to UV light or sunlight
- Wash print in water then allow to dry
Preparing Paper
The cyanotype process uses iron-based chemistry. It was realised in the early C19th that some iron compounds exhibited sensitivity to light, and this was developed and led to the cyanotype process.
The chemistry is fairly simple. You have two iron compounds which you use to create a solution. Separately, neither is light sensitive, however when mixed it becomes light sensitive. There are some variations on the chemicals that you can use, but the two commonest ones are Ferric Ammonium Citrate and Potassium Ferricyanide. Photographic suppliers stock the chemistry either in pre-measured amounts in plastic bottles that you make up, or as the raw chemicals which you can weigh out and mix yourself.
Once the solutions have been mixed together, you have to work in subdued light. The main thing is no ultraviolet light (UV). A darkroom red light or safe light is fine. You then paint the chemistry onto your medium. I tend to use watercolour paper, which is a cotton rag paper. Most types of paper will work, but you may need to test it. You can paint the mix onto fabric, but I have not tried this.
Once the paper is dry it needs to be stored in a light tight container or bag. You can buy suitable plastic bags from photographic suppliers. You need to treat it the way you’d treat traditional photographic paper – keep it in the dark, double seal the end of the bag to keep light out. Always re-seal the bag. Ideally put the bag inside a box of some sort.
Creating Negatives
You can make photograms by placing objects on the prepared paper, e.g leaves and petals. Other than no negative is required, the process is otherwise identical.
Cyanotype printing is a contact print process: the negative (or objects if making a photogram) is placed directly on the paper, so the image is therefore 1:1 with the negative size. How do you get around this? The answer is to create a large digital negative which is the size that you want your image to be. You can use editing software such as Lightroom or Affinity to turn the original positive digital image into a negative. Convert it to black and white first, then use the tone controls to flip black and white and you will have a negative (I’m not discussing how to do that in detail here – I will write another post about creating digital negatives).
You need a laser printer to print the negative onto acetate sheet that’s designed for use with laser printers. Be very careful about this: acetate that is not designed for a laser printer will melt going through the fuser unit. As a general rule, inkjet printers don’t work for this process – the only way to be sure though is to experiment.
By printing onto acetate you can create an image up to A4 in size without too much trouble.
You should now have a negative on a sheet of acetate that is the size you want.
Making the Print
You need to hold the negative flat against the treated paper and then expose it to ultraviolet light. There are two things here: some sort of frame and your light source.
You can do this in many ways, the only requirement is that the negative and paper don’t move during the exposure. You could simply get a a heavy piece of cardboard the right size, place the paper and negative on top, then cover with a piece of glass or acrylic, and use some bulldog clips or elastic bands to hold it all together.
You can use a basic picture frame – anything that will hold them flat and together without moving. You can use a contact print frame or there are bespoke frames available for making cyanotypes, but you don’t need one.
Now we’re ready to expose the print. The effective ISO of teh cyanotype process is significantly less that ISO 1 – more like ISO 0.01 or even ISO 0.001 – it is very slow.
You can use daylight, or you can buy UV LED strip lights online for less than £15. The UV lamps are more consistent and quicker than dayight. You have to experiment to determine the required exposure. Daylight in the UK is likely to need somewhere in the range of 15 to 30 minutes exposure. It varies depending on the time of year and how high the sun is in the sky, as well as on weather conditions. There will be UV even if it’s cloudy. Depending on the set-up, the UV LED light will be around 10 to 15 minutes.
Let me explain how you determine the exposure.
The process is the same whether you use sunlight or LEDs. In my set-up, I have a pair of UV LED strip lights held about 20cm above the paper. You make a test strip the way you would in the darkroom and printing. Use something completely opaque to cover your frame leaving a 2 inch strip exposed (I used a piece of card). I then exposed for 5 minutes. Move your card across two inches to expose more paper. Expose for 2 minutes. That means you now have one strip that has exposed for 2 minutes and one for 7 minutes. Repeat several more times. I ended up with a test print that had strips which had been exposed for 2, 4, 6, 8, 10, and 13 minutes.
You then put the print in a sink or bowl of cold water, which washes out the unused chemistry. This develops the print. You will be safe to look at the print in full light after a couple of minutes. It takes around ten minutes to wash it all out. If you don’t wash it all out, the image will become fugitive.
Examining the print, I couldn’t see anything until the exposure was around the 6- or 8-minute mark. I decided somewhere around 11 minutes was correct. I knew from a previous test it was going to be around this length. A common mistake is to underexpose and to see nothing and assume it’s all washed off or something.
Now that we know what exposure to use, we can make our proper print.
What I Used
Here’s what I’ve tried. I use watercolour paper. I’ve opted for Saunders Waterford Mill 140lb (300gsm) rough cotton rag watercolour paper. I used ‘quarter sheets’ which are 16” x 12” (c. 400mm x 300mm). I have made my own chemistry by mixing the raw chemicals, and used the prepared bottles: both work fine, but the ‘make your own’ is more economical.
I bought a pair of UV LED strip lights from Amazon for about £15.
I did buy a proper contact print frame for making cyanotypes. That was expensive at around £40. A cheap picture frame would work.
I bought a pack of laser print acetate sheets from Amazon. This was £5 for ten A4 sheets.
Conclusion
Cyanotypes are permanent and lightfast, provided they’ve been properly washed. You will need to hang them up to dry. When dry, they may need pressing between some boards under a heavy weight to flatten them (depends on the paper you’ve used).
The classic blue colour is what gives cyanotypes their name. However, you can modify the resultant colour in various ways. Some involve modifying the chemistry, others include something as simple as adding tea to the wash… I will talk more about this in future posts.
If you don’t want to make your own cyanotype paper, you can buy paper that is pre-treated and ready to use. I have used it – it’s readily available in A5 or A4 sizes. It does tend to be quite a lightweight paper though.
Rough watercolour paper has an issue in that it treats the chemistry the same way it treats watercolour paint – the texture means a brush stroke will catch the high points in the texture but might not catch the low points. This is effect is highly desired in watercolour painting and it’s why artists use rough paper instead of ‘Not’ or ‘HP’ (hot pressed), both of which have a smoother texture giving a more consistent laying down of colour.
