Pere Rius
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| Tom Hart |
We are going to develop the subject in two parts:
First part (in this article)
1. A bit of history
2. What does it entail?
3. Required material
4. Emulsion preparation
Second part (this article)
5. Emulsified paper
6. Creating photholits or frames
7. Exposure process
8. Developing and drying
1. A bit of history
The English scientist John Herschel (1792-1871) discovered a photosensitive mixture in 1842, which allowed transferring blue images to paper.The botanist Anna Atkins in 1843 produced cyanotypes to illustrate her book "British Algae: Cyanotype Impressions". She is considered the first woman photographer.
It appears that to photographers of the time, however, the blue copies result does not please them and the procedure is used less and less until it falls almost into oblivion. However it began to be used for other purposes such as to make copies of technical drawings.
Today this procedure has resurfaced with force and interest for its simplicity and versatility.
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| Anna Atkins |
2. What does it entail?
To do cyanotypes we need two chemicals: iron and ammonium (III) citrate and potassium ferrocyanide. A support which is capable of absorbing the solution such as paper, wood, textiles, etc. Various objects or photolith/negative to make the frames. A glass plate to make contact. A sunny day or an alternative source of UV rays. Plenty of water for development.Very briefly the procedure is to apply the photosensitive solution onto a support (paper, textile, wood ...) and let it dry in the dark. Once dry, put over it a photolith and a glass that allows uniform contact. Instead of photolith we can easily use various objects and place them directly over the sensitive support. Whether we have chosen a photolith or objects, we need to put it under the sun for a few minutes for the sun's UV rays sensitize the support. Simplifying: the white areas of the photolith will let through the UV rays and the black areas, no. With the objects something similar will happen, the space occupied by the object will prevent the support from being exposed. Later we develop with plenty of water. The unexposed portion of the emulsion will dissolve with water and disappear. The exposed part reacts giving way to a compound that does not dissolve in water and acquiring the characteristic cyanotypes’ blue. Finally we let the work dry.
From here we will see step by step what we have hitherto explained very synthetically.
3. Required material
Safety note: Some of the products listed below are toxic and must be handled with special care. See the package security information provided by different manufacturers or distributors.3.1 To prepare the emulsion
Iron and ammonium (III) citrate
Potassium ferrocyanide
Distilled water
1 kitchen scale to weigh chemicals
2 DIN A5 white paper
2 brown or opaque bottles with capacity of 100 ml or more.
2 adhesive labels
2 latex gloves or similar for protection during the handling
2 plastic spoons
1 funnel
3.2 To prepare the support with the emulsion
2 bottles with solutions A and B
2 syringes, for each of the solutions
1 container where we will mix solutions A and B
Brush to spread the emulsion
1 container with water to clean syringes, brushes, etc.
1 paper towels roll
3.3 For exposure
Glass plate (which does not filter UV rays)
Wood fiber plate or similar
4 fold back clips
Photolith or negative / Miscellaneous objects
3.4 For development
Area with running water (shower, sink...)
3.5 For drying
Area for drying (table, shelf, clothes...)
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| Skylitup |
4. Emulsion preparation
We will focus on the basic formula. Although we can find on the internet and other sources variations of the formula for cyanotype.4.1 Basic formula to prepare 200 ml of solution
20 g of Iron and ammonium (III) citrate
8 g of potassium ferrocyanide
200 ml of distilled water
4.2 Preparation
We fill each bottle with exactly 100 ml of distilled water
We label one of the bottles with the words "A Cyanotype" and the other "B Cyanotype"
In the "A Cyanotype" bottle we pour exactly 20 g of Iron and ammonium (III) citrate. To do this we use the kitchen scale to weigh the exact grams, with the plastic spoon and the folded DIN A5 we pour carefully the chemical inside the bottle with distilled water. Tightly closed with the cap and shake until the chemical is dissolved.
In the "B Cyanotype" bottle we pour exactly 8 g of potassium ferrocyanide. To do this we use the kitchen scale to weigh the exact grams, with the plastic spoon and the folded DIN A5 we pour carefully the chemical inside the bottle with distilled water. Tightly closed with the cap and shake until the chemical is dissolved.
We throw away the spoons and papers. We keep the two bottles in a dark place. Done!
In the next part, we will see how to emulsify the paper, how to create photoliths or frames, the process of exposure and development and drying cyanotypes.
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| Yen-Chi Chen |
