In parallel with the indigo trials we wanted to explore silk casting following protocols detailed in Rockwood et al., “Materials fabrication from Bombyx mori silk fibroin” [Nature Protocols 6, 1612 (2011)]. The setup is to incubate degummed cocoon silk in 9.3M LiBr for four hours at 60C, which breaks down the silk fibers into a viscous liquid, and then dialyze (desalt) this liquid for 48 hours in water to pull out as much of the LiBr as possible:

After desalting, there are some “optional” (as in, probably a good idea to stabilize the silk fibroin solution and definitely recommended for any sophisticated bioengineering or nanotechnology applications, but in practice skippable for the kind of bulk work I’ve been doing) centrifuging steps to clear out any residual undigested fiber/dirt from the cocoon stage. Stored in the fridge, the solution generally lasts 3-4 weeks before it goes off (“solidifies” into a hydrogel in the storage tube such that you can’t use it for casting anymore).