The cyanotype process is very similar to that of the salt print, although it can be used in a more versatile way and can be applied to cotton, wool, wood, and even non porous surfaces such as glass or acrylics.
- Hake brush. No metal ferrule and no metal by the bristles (you can’t wash hake brushed with warm water).
- Coating glass rod
- Contact printing frame. Cheap clip frames will do too or any piece of glass to flatten negatives and objects.
- Potassium ferricyanide red.
- Ferric ammonium citrate (green)
- Two empty bottles to store the chemicals separate. Dark brown or black are better.
- Distilled water or just water. Ideal Ph for water is Ph4, so slightly acidic.
- Sunlight or any UV light source.
- Recipient for mixing the solutions.
- Plastic teaspoon
- Measuring jug
- Developing tray
- Substrate for coating. Paper, clothes etc.
- Hairdryer if you want the prints to dry faster.
The process step by step:
Step 1 – Coating
You can coat many different types of paper, even coloured. Cheap acid papers such as newspapers work very well.
You can also print on fabrics, to do this it’s best to immerse the fabric into the photo sensitive formula.
If using paper you can coat it using a hake, foam brush or coating rod. You can do this in normal light. Apply the photo-sensitive solution quickly using gentle vertical and horizontal strokes. It will depend on the paper that you use on how much you can put on.
Step 2 – Drying
Once you have coated your paper let it dry in low light or semi dark conditions. If you use a hairdryer hold it far away and from the opposite side to the solution.
The paper should be properly dried, any moisture left in the paper will become an instant developer since this is a water development technique.
Step 3 – Exposing
You can use daylight to expose but the atmospheric conditions will effect your exposure.
During the wash and development stages you will loose density so it is important that your highlights are able to print. One of the most common problems with cyanotype is underexposure. The denser the negatives require longer exposures.
The best way to check the exposure is to look at the print. The darkest areas should be turning to a dull grey and there should be some yellow visible in the lightest areas.
The exposure should vary between 8 minutes under UV light to 1 hour on an early morning. It helps to write down your exposure time to be able to evaluate your progress over a printing session.
Step 4 – Development
Traditionally cyanotypes are developed with running water. The best water to use would be slightly acidic, Ph4 or distilled water. You can extend the tonal range without lengthening the exposure by adding vinegar to the water bath but you will loose contrast. The more vinegar you add the less contrast you will have.
Step 5 – Wash
After exposure and development you will need to wash your print in running water for 5 – 15 minutes or until the highlights have cleared to white and you shouldn’t see any green-yellow in the water. Make sure not the wash it for too long as you’ll lose pigmentation in the highlights.
After you have washed your cyanotype you need to leave it to dry. As it dries the blues will get darker.
You can accelerate the process by adding Hydrogen Peroxide 3% to a water bath, between the development and the washing steps. You can mix this with the water without having to worry as its used to clean wounds and as a mouthwash. This won’t add anything to the print that wouldn’t naturally happen during the drying process but it is interesting to see.