Popular Science, syyskuu 1920
On the coast of Costa Rica, near Cocoa bay, the juice of a certain shell-fish, which abounds there, is used for dyeing.
The process is laborious, since only a small amount of the liquid dye can be obtained from each fish. The way this is done is by blowing one's breath into the shell, whereupon a few drops of a greenish liquid ooze out. This is collected in a clam-shell, and the thread to be dyed is drawn through it.
Exposure to the sunlight turns the color into a rich purple that is absolutely fast in quality.