Cyanotype - Method: - Mixing the Chemicals

 

Step 1. When you are ready to coat your paper, combine equal amounts of solutions A and B under subdued light such as a red or yellow safe light. For optimum results, try to mix about the amount needed during one day.
Step 2. Brush the mixed emulsion on the paper or other surface taking care to apply the coating reasonably thickly as possible but not so thickly that it would drip when hung to dry. It is important that a brush is used without a metal ferrule as this will contaminate the mixture. More info on applying the emulsion.
If you have to use a metal ferrule make sure that you only dip the end of the brush in the mixture, the metal ferrule can also be covered with plastic tape. While they are more expensive, brushes can also be obtained that have a stainless steel ferrule and these seem to have no effect on the mixture.

Additional coating information:

While the emulsion is sitting, the chemicals can tend to separate out at different levels in the liquid so just before you coat the paper give it a stir.

Use gloves and other protective equipment

Applying the emulsion too thickly can create a situation where the top layer of the emulsion becomes dark on exposure and blocks the light from reaching the lower layer, so that in the developing stage both layers wash away.

Experiment with emulsion thickness -

Experiment with application techniques, foam brushes can be used, foam rollers can give and even coating.

Aberrations can be incorporated as part of the work.

Be aware that some papers are fragile and may need taped down to a board for coating and processing, also some papers may need sizing to stop the emulsion soaking into the fibres of the paper.

Step 3.

 

Dry the paper in darkness or subdued light and keep in darkness until use. If you are coating a great number of sheets a drying rack is ideal, but be careful that there is no wet emulsion or contaminants on the rack where you place the paper.

A hair dryer can be used to speed the drying up. Some manuals recommend using the sensitized paper with in 12 hrs. I once forgot about some paper in this state and used it after about 3 weeks without any great difference. This did not seem to effect the sensitivity: The only effect was that the tonal quality might have been a little softer.

3. Place the paper in a light tight drier, or hang up to dry in darkness. Once dry it is best to use the prepared paper within 12 hours. 4. Expose the sensitized paper to sunlight with the negative laid in contact on top of the emulsion and a thick piece of glass on top to give better contact. (For perfect contact, a more sophisticated means of achieving this are discussed in various books on the subject). The exact exposure time will vary with sunlight conditions and experiments might be necessary to obtain good results, in bright sun the time will be about 20 mins. Finished exposure is indicated when the image appears to be one stop over exposed. 5. Develop under subdued white light in a try of running water until all yellow races from the sensitizing solution have disappeared. For a more intense blue dissolve a few drops of Hydrochloric Acid in the wash tray before inserting paper, or after development in water, soak in a tray of water with a few drops of ammonia for a about 5-10 seconds 6. Wash paper for another 10mins in running water and dry either by hanging up or tacking to a board with gummed tape. The later will avoid curling up but the print will need to be carefully cut out from the gummed surround with a sharp blade. While it is best to wipe all surfaces when the chemical mixture is wet, any marks left by the emulsion on working surfaces that have dried can be cleaned up relatively easily with water.