Cyanotype exposure time
There is no single exposure time for a cyanotype. The two sources we could quote give different ranges, and the maker says the time depends on conditions. Here is what each says.
What the sources say
| Source | Light | Time |
|---|---|---|
| Jacquard, Cyanotype Kit | sunlight or UV | 10-20 minutes, depending on conditions |
| Jacquard, quickstart guide | sunlight | 10 - 20 minutes |
| Getty Museum, on Anna Atkins’s process | the sun | five to fifteen minutes |
In their own words:
“Coat the included Hahnemühle Platinum Rag Fine Art Paper with the sensitizer and, once dry, create prints by exposing to sunlight or UV (10-20 minutes, depending on conditions), using the included glass printing frame and objects or a film negative to create an image.” [Jacquard, Cyanotype Kit]
“Expose to sunlight 10 - 20 minutes” [Jacquard, Cyanotype Kit quickstart guide]
“The entire package is placed out in the sun for five to fifteen minutes.” [Getty Museum, Anna Atkins, British Algae]
The ranges overlap between 10 and 15 minutes and are not the same measurement: one is a modern kit’s instructions, the other a museum essay describing how a cyanotype is made. We do not know why they differ and will not guess. Jacquard says the time depends on conditions; we have no source that turns conditions into a time, so this page gives no UV-lamp time, no sun-angle or UV-index table and no test-strip method.
Too short, too long
Jacquard’s troubleshooting sheet says what an exposure that is too short looks like:
“The print was probably not exposed long enough. The light source may not be intense enough. Or the negative may be too dark. Over-washing can also result in pale prints.” [Jacquard, Cyanotype Tips and Troubleshooting]
And one that is too long:
“The print may also be over-exposed. Try reducing the exposure time.” [Jacquard, Cyanotype Tips and Troubleshooting]
Keep it dry
“Do not wet fabric or paper before or during exposure.” [Jacquard, Cyanotype Tips and Troubleshooting]
What the app does about exposure
The Cyanotype app does not give an exposure time. Its Digital negative sheet says to print on transparency film at 100% and adjust exposure to your chemistry. It makes the negative; the time is yours to find. See the digital negative page, or how to make a cyanotype for the whole process.
On your phone: Cyanotype
For iPhone and iPad.
The app shows your photo as a cyanotype print first, in seven looks, with print sizes and matte borders, so you can see the blue before you coat anything. Then it exports the digital negative at full resolution: black and white, inverted and mirrored, and for 4 × 5, 5 × 7 and 8 × 10 paper at the resolution that prints at the paper’s size. It all happens on the device. There is no account, and the app makes no network connections.
How this was checked
Statements about the process, its chemicals, safety and history are quoted word for word from the maker’s instructions (Jacquard), the Getty Museum and the Photographers’ Formulary safety data sheets, and linked where they appear (checked ). Where we could not fetch a source for a fact, we left the fact out, so this section gives no concentrations or amounts of chemicals: use the instructions and safety data sheet that come with what you buy. The digital negative tool is compared by an automated test with the Cyanotype app’s own code. If something here is wrong, tell us at a@noshu.net.