First, the birch fungus. That fermentation vat resulted in nothing, niente, nada :) I have no idea what went wrong, the acidic solution had a wonderful orange-brownish color, but the wool did not absorbed any of it :( So, that was that.
But now the good news! The oak birch vat worked and I got a lovely color as result :) The photos are from the first skein I dyed. I let this one stay first 2 hours in the acid vat, then 20 minutes in the basic vat, then overnight in the acidic vat and again 20 minutes in the basic vat. With breaks in between for drying. The result is a lovely caramel color. I like it a lot :)
Now about the technicalities: I had around 1.5 kg bark and by now I dyed around 600 gr wool. I used lemon juice for the acidic vat and caustic soda for the basic vat. The vat is still good, but I will stop now because I have others waiting in line to be tested :)