Cyanotype:
Basic formula (for 100ml each):
"A" 25gm Ferric Ammonium Citrate (green)
"B" 9gm Potassium Ferricyanide

All chemicals from Tri-Ess Science, Burbank, CA (818-848-7838).

Note: Refrigerate Part A between uses if possible.

Just before use mix three parts "A" and two part "B".

Coating: Use 9ml for 16x20 (17.5x21.5)
Use 4.5ml for 11x14 (12.25x15.25)
Use 2.5ml for 8x10 (9.75x10.75).

UV light source type F25T8-350BL bulbs (or 10AM to 2 PM sunlight)

Negatives for cyanotype typically are developed 40% longer than typical.
This recommendation varies significantly with the paper used.

Note: All chemicals used are poisons, should be kept out of the reach of children. Wear gloves when mixing, coating, and developing.