I finally got around to trying the cooked-down blueberry ink, which turned out way better than just trying to juice it without cooking. Many thanks to the Druid's Garden blog for the instructions. Be sure to check it out. Here are some writing samples alongside my uncooked pokeberry juice ink. Over time, we'll see how it ages in the bottle and on the page... The blueberry ink goes down pink but then oxidizes to blue as it dries. I didn't use any gum arabic. It oxidizes a lot slower on 100% cotton paper than on sugarcane paper. It's also rather slow to dry. Sample written with a Coit dip pen: Sample written with MusinkMan's oblique flex dip pen: Samples written with a glass pen: