Still no luck with the blue dye. I tried another approach this time, making up a solution with alum as a mordant and pre-soaking the leather. That didn't seem to make much of a difference, other than stiffening the leather up. The blue just rubs off with a damp cloth again.
Now I'm starting to wonder if the issue has more to do with the indigo I'm using. All of the instructions I see for fabric dying with indigo calls for all kinds of processes to dissolve the pigment into the liquid. I'm wondering if maybe the "indigo" being used in my recipes is somehow different from the dry powder that I'm getting modernly.
Whatever the case, that's now five attempts using two different recipes, so I think I'm going to move on for now. I`m running low on indigo powder anyway. I`ve ordered more (plus some gallnut extract and lye for other recipes) but may as well work on another colour so my A&S project doesn`t stall.
I've started work on a red dye recipe. First step was to mix a bit of water with some brazilwood dust and let it soak overnight, which is happening now. Tomorrow I'll add some more water and boil it for a while, and add in some gum arabic. Hopefully this one will work better.
As part of the recipe I had another Italian measurement to figure out, this time a quarti.
Just to document what I found, this is what I used:
Quarti = 0.6625 litres
Post period definition of a Quarti is that 1 amphore of wine = 16 quarti = 137 english gallons