After the technique cyanotype on paper, I try another technique – cyanotype on the glass.
Liquid emulsion applied to glass and washed with water.
Task sounds simple. Is it?
- Potassium Ferrocyanide 28g
- Ferric Ammonium Citrate 82g
- Oxalic acid 3g
- Gelatine 80g
- Water 600ml
The process begins by mixing 3g of oxalic acid in 600ml of distilled water, followed by Potassium Ferrocyanide 28g, Ferric Ammonium Citrate 82g, and finally 80g of gelatine. Prepare everything in cold water. For gelatine, the water should be cold because the gelatine particles will not stick to the lumps, and it will be easier to dissolve it. We must mix the solution until everything is dissolved. The next step is to heat the pan to 65 degrees Celsius with constant stirring. When the liquid becomes viscous – almost like the water, we stop heating up and stirring. This liquid is now prepared to filter which can be done with an ordinary coffee filter. The emulsion is now finished!
After filtration, store the finished emulsion in a dark, light-tight container. Its lifespan is around one year. You can use foil containing the films or photo paper, or if you have none of this – a plain aluminium foil to wrap the jar in which emulsion is stored. It is recommended for the emulsion to “stabilize” for a day or two before use. The main difference with ordinary cyanotype technique is its substrate, which is now glass instead of paper.
2mm or 3mm thick glass is used depending on the photo format. It is desirable to smooth the edges of the glass – that way we do not risk injuries when handling the glass.
The glass must be thoroughly clean of grease and dust. There are many ways to clean the surface, but careful cleaning with a coarse sponge and dishwasher detergent will be enough. After cleaning it is crucial to rinse the glass with water thoroughly to avoid any possible residue of cleaning substance or any cleaning agent. Wipe all water off the surface and dry it thoroughly. Keep in mind that every fingerprint will leave oily swell on the emulsion so handle the surface with care.
Place the jar with emulsion in hot water (approx. 65C) and wait until the emulsion is entirely liquid. Prepare the glass and the spoon which you will use to scoop the hot emulsion. The emulsion is poured into the centre of the glass until it covers approximately 70% of the surface, slowly pouring from edge to edge, and the rest is poured into a separate container. Filter the emulsion residues before returning to the emulsion jar to avoid contamination with possible dust or debris from the glass. The coated glass plate is placed vertically to the blotting paper to allow the emulsion to dry. Excess emulsion accumulates at the bottom edge of the plate and it is necessary to move the plate several times to remove the excess emulsion. Drying speed depends on the temperature and humidity in the air. Do not dry the glass with a blow dryer or over strong heat sources as the emulsion will start to melt and will be unusable.
SOME MISTAKE WHICH COULD HAPPEN
Impatience does not pay off. If you dry the plate with warm air, the emulsion will likely melt at some point. In the upper right corner of the picture on the left you can see how the emulsion responds to leftover particles after cleaning plate.
Click photos for a larger view
On the right picture you can see how the emulsion disappeared on thin section and how is melted on the girl’s forehead. Other irregularities result from insufficient cleaning of the glass