I just tried to make sawtooth oak acorn ink last week, but I got distracted at the very end of the process and burned the dang thing up! Aargh! I don't have the will to try again right now (and I still haven't gotten around to scrubbing out the pot!) Maybe I'll try again next year. I wasn't going to make it into an iron gall ink, though-- I was processing it the same way I do black walnut ink (i.e. repeated cooking down, adding more water, cooking it down, making it as saturated as possible). Acorns don't have much tannic acid, or at least not compared with oak galls, but they can make a nice ink similar to black walnut. I have made a fermented acorn iron gall ink (rather than cooked down) in the past, but it wasn't very successful, probably because it had too little tannic acid. I've never heard of any acorn containing more than 5-10% tannic acid, though, and some like the white oak have even less than 5%. Here's a very basic idea:
- Pin Oak
- Red Oak
- Bur Oak
- Sawtooth Oak (6-9%)
- Black Oak
- Live Oak
- English Oak
I have a theory that during heavy rainfall years, the tannic acid in acorns becomes diluted somewhat. Squirrels won't generally eat a high tannic acid-content acorn unless there is nothing else to eat (it's too bitter). So look for acorns that the squirrels aren't touching if you can (like I said, this can change year to year... some years the squirrels will eat the normally bitter sawtooth oak acorns here, but this year they don't seem to be touching them... we had a lot less rain this year than last). It's just an observation.
I recommend keeping a close eye on the ink while you cook it down. It'll reach a stage after some extended cooking where it will begin to caramelize, and after that it can scorch very easily. When you start to see a caramelized film form on top, drop the heat to low, so that it is only barely steaming and only continue to cook it down as far as you think necessary (make writing samples all the while).
eta: this is a scan of the fermented acorn iron gall ink I made in 2012. As you can see, the color is quite thin and gray (and as it aged it turned greenish). You can read about the process here, but I don't consider it a very good ink, especially compared to the oak gall ones.
Edited by fiberdrunk, 10 November 2014 - 02:17.