How long can coated cyanotype paper be stored before UV exposure?
Asked 10/1/2021
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If I coat a surface with traditional cyanotype sensitizer, let it dry, and then store it in a fully lightproof bag, how long is it likely to remain usable before I expose it to UV light? I'm asking about home-coated material rather than pre-sensitized commercial paper.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
4y ago
2 Answers
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Given the fact that presensitized cyanotype ("sun print") papers are sold commercially, it seems that at a minimum coated and dried cyanotype sensitizer can be stored for at least several months.
In practice, the limitation will be on how rapidly either stray UV or other environmental factors prompt the reaction between the ferricyanide and the ferric ammonium citrate (presuming traditional cyanotype). If thoroughly dried without heat and kept in a thoroughly dark storage environment, this rate is very slow.
For home sensitized paper, I've kept it only a few days before exposing, but I've read of people keeping it for at least a few weeks. Few who coat their own will do so in quantities requiring much longer storage, but it seems it's possible -- with the proviso that commercial precoated paper may have a slightly modified sensitizer compared to the traditional Herschel formula from the 1820s.
Originally by user89902. Source · Licensed CC BY-SA 4.0
user89902
4y ago
0
Generated from our catalog & community — verify before relying on it.
Properly coated, fully dried cyanotype material can remain usable for quite a while if stored in complete darkness. Based on the community input, commercially pre-sensitized “sun print” papers show that coated cyanotype surfaces can last at least several months under good storage conditions. For home-coated paper, people commonly use it within a few days, but reports suggest it can often last for several weeks as long as it is thoroughly dried without heat and kept in a truly dark, protected environment.
The practical limit is less about a fixed expiration time and more about storage conditions: stray UV, moisture, heat, and other environmental factors will gradually reduce sensitivity or cause unwanted reaction. So the safest guidance is:
- dry the coated surface thoroughly
- store it in a fully lightproof bag or box
- keep it cool and dry
- use it sooner for the most consistent results
In short: expect days to weeks for home-coated material, and potentially several months under ideal conditions.
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