Iron gall ink, part 2

I finally braved the goo! I'm sparing you the gory pictures, but it wasn't as bad as I thought it'd be. I strained the ground gall into a bowl (see picture below, and yes that's exactly what it looks like -- thankfully it doesn't smell like that). Then I mixed the ground galls with another cup of water, swished it around and strained it again. Finally, I took out handfuls of the mush and squeezed them hard in my hand to get the last of the liquid out. After it was all said and done I had about 5 or 6 cups of gall liquid.

I picked up some iron sulfate from Seattle Pottery, which is the yellow powder in the white bowl below. The matter of obtaining iron sulfate hasn't been an exact science. If you do a Google image search for "iron sulfate" you'll see a lot of pictures of green powder, some pictures of a white powder, and a few pictures of a yellow powder.  Which is the one I need?  I'm going with the yellow stuff from the pottery supply place.  We'll see how it turns out.  So far, so good --

My apologies for the fuzzy picture below. Had I known the liquid would change so quickly and dramatically after adding the iron sulfate I would have tried harder to take some good before pictures. But below is the best one I have. Prior to adding the iron sulfate, the gall liquid was a reddish-brown color and very watery and transparent --

After adding the iron sulfate it changed quickly right before my eyes, becoming a very dark black color and thickening somewhat. At first it was brown-black but as it sat it became more purple/blue-black. It even stained my fingers black as I worked with it.  Definitely potent stuff, at least in terms of staining. It's a little hard to tell in this photo, but this is what it looked like after adding the iron sulfate --

Now to set it aside to sit for a few more days before the final step...