|Alkanet with Soda test|
Blackberry: Probably the most flexible source of purple dye for anthotypes, blackberries can be used many different ways. If you just crush the berries and strain the juice without any dilution at all, it provides an intense, Barney-like violet. Diluted, the color is softer but the exposures are shorter. If you boil the blackberries before squeezing them, the color will be darker. If you filter the boiled blackberry, it reduces the darkness and shifts the color closer to a red-violet. As usual, boiling the dye will slow your exposure times and in general produce less useful results.
There are lots of possibilities and all of them give good results. Generally under a week for your exposures. Also note that blackberries respond well to moisture in the exposure, sometimes creating interesting halos if fresh plants are used and the exposure frame isn't sealed up tight.
There are so many permutations of blackberry, I'll just link my Flickr dye tests.
|Blueberry, filtered fine|