What is a Calotype?
The Calotype (meaning "beautiful"), or Talbotype are paper negatives that Fox Talbot invented in 1840. The Calotype was an improvement over the photogenic drawing process that preceded it.
The paper was first coated with a solution of silver nitrate followed by a solution of potassium iodide. This formed potassium iodide and excess iodides, they were washed from the paper and then the paper was dried.
The iodized paper was then treated with silver nitrate, glacial acetic acid and gallic acid - this was known as gallo-nitrate of silver. Still damp, the paper was placed in the camera and exposed.
The exposed image was developed with a mixture of gallic acid, acetic acid and a small amount of silver nitrate. The image was fixed with sodium thiosulfate and then washed again.
1. Paper: This is, without doubt, the most critical component to the process. It seems difficult to find good paper nowadays - good as in consistent and reliable. Quinn offers some suggestions in his online course and in person workshops on the Calotypes.
2. If the paper you are using is to akaline, you will need to acidify it before using it.
3. After acidifying, size and iodize the paper. Hang the paper and allow to dry.
4. Float the paper on a silver/acid bath for 3 minutes.
5. Exposure the paper (typically you can start with 2 minutes at f/8 on a sunny day).
6. Float the exposed image on a bath of gallic acid. Development can be as short as 10 minutes or as long as 20 - maybe longer - but don't fog the image.
7. Wash in a bath of distilled water for 5 minutes.
8. Fix in a weak solution (10%) of sodium thiosulfate - fix #1 for 5 mintues.
9. Fix in a weak solution (10%) of sodium thiosulfate - fix #2 for 5 mintues.
10. Wash for 30 minutes in running water.
Calotypes were usually printed on Salt paper - you can print them on Albumen paper as well.
If you are interested in learning the Calotype process, you can check here for Quinn's next course or lecture on the process.