Book of Kells Project: Oak gall, er, Acorn ink

Or, "What to do when Snubbed by Gall wasps".

 

Alas, some corners will be cut in the interests of convenience. For instance, I will not be using vellum. Smooth watercolor paper will have to do. Frankly, the monks might have preferred paper if they’d had access; the ability to make even sheets of paper, in standard size and thickness would have taken a lot of headache out of the picking out quality calves skins.

But gall ink is something anyone who lives near oak trees can make. Or could if we had gall wasps.

Fortunately acorns contain enough tannin to be going on with. To make ink you need to leach the tannins out of the acorns. The advantage of galls is the high concentration. In absence of galls, one just has to use more acorns and reduce the ink brutally. As it is, I regularly forage for acorns in the fall as a wild food source, so I had enough left over to experiment with.

Oak gall (or acorn) ink is a marriage of tannin and iron salts(iron sulfate). This technique will work with any tannin rich nut, bark, or hull, but different plants will have different shades. Oak gives a color anywhere from an ash greyish brown to true ink black, depending on concentration. Chestnut is brown to a very dark blackish brown, but if you have oak ink beside it, you can see it’s not true black. Even coffee will give a dark brown, but people who have experimented say the ink is oily or shiny and doesn’t flow well. Others recommend walnut or sumac. There’s certainly plenty of room for experimentation. But I quite like the results from acorns, if the gall wasps insist on snubbing us.

The first step is to gather acorns in the fall. If you are foraging for food, use the cracked, slightly moldy, squirrel nibbled ones. It won’t matter for making ink. To learn, start with a couple of cups unhulled. Using a nutcrackers, hammer, or even a rock, crack all the acorn shells. You do not have to hull them. There’s tannin in the shell and nut; you just want to crack it so the nut will leach quicker.

Dump the acorns in a waterproof container large enough to hold twice the amount with at least a couple inches to spare. I use a large plastic box of the sort nuts come in. This has the advantage of being able to see at a glance how dark the water is getting and a lid that keeps the squirrels –and any other wild freeloaders—out. But any waterproof container will do. Fill the container with enough water to cover the acorns plus an inch. You can use more, but your reduction will be longer.

Set aside in a safe place; if you have a lid you can put it outside and let it sit for at least a week until the water is a dark brown. If you don’t get to it immediately, no problem. It won’t go bad, though if you don’t have a lid, it can evaporate.

[iron salts img]

Meanwhile, you need to make the iron salts. Get a glass jar that’s at least 8 oz. I prefer a pint jar. DO NOT USE A LID. The mixture you are making will produce gasses that if contained could explode. The gasses themselves are (relatively) safe. You need iron bits—scraps like rusty nails and wire are used, but I usually have iron oxide from other art projects and I prefer it for evenness. If you are using garage and shop scrap iron, try to get as much dirt and soil off. If you’re using iron oxide powder, two tablespoons should be more than enough. If scraps, a quarter to half a cup. Put the iron in the jar, then fill the jar with enough vinegar (white is best) to cover them completely. Set this jar in a safe place it will not be tipped over, is out of reach of pets and children. Outside if fine IF it is sheltered from rain water. Water will dilute the solution and make it less effective when interacting with tannin.

If you mix iron solution up the same day as the acorns started soaking, it will be plenty ready in a week. In a couple days, you’ll see bubbles in the vinegar as it interacts with the iron. Gently stir the mixture if it seems to be too calm.

Wait a week.

Now most of the acorns should be waterlogged, sitting on the bottom of their container . The water should be a dark brown, the darker the better. Empty the whole mix, nuts, shells and tannin water, into a stainless steel or enamel sauce pan. DO NOT USE CAST IRON. That can work, but it’s hard on the pot unless it is a dedicated dye/craft pot. Heat to boil, then simmer with a lid, for an hour.

Now every bit of tannin has been extracted. There will be some oil on the surface. It’s just acorn oils, and won’t affect the finished product. You want to strain the acorns out. I use a strainer lined with muslin cheesecloth and two pans. You might need to strain a couple of times, folding the cheesecloth in half. Ideally you want to remove all small particles. Remember you are making ink.

Discard acorns and the acorn grit in yard compost if you can.

Now you should have a dark brown liquid clear of debris. In a small stainless steel pan boil it then reduce to a vigorous simmer. Stay in the kitchen or nearby to keep an eye on it. It can reduce fast, in a half an hour , especially a small test batch of a pint , and you don’t want to burn the pan. If you started out with a cup, reduce it to a quarter of that. It will barely cover the bottom of a small pan, but this is the concentration you need if the gall wasps have snubbed you. Some people use a double boiler method. If I start with a pint of boiled , strained acorn tannin, I expect to have about a half a cup.

Once is reduced, cool to room temperature and transfer to a 8z or pint jar. You want some extra room. Alternately , before transferring the liquid, you can warm the jar with hot water, dump the water, then fill it with the tannin solution straight from the stove. If you don’t warm the jar it will crack.

Once the jar with tannin solution is cool, get the iron solution. I don’t have precise proportions because I’ve only done this a couple of times. But if in doubt start with less and add more by small bits. DO THIS OVER A SINK.

For a cup of reduced tannin, add a tablespoon of iron salts to start with

For a pint, start with two tablespoons.

Immediately there will be a reaction, a fizzing of bubbles. If your container is big enough you should be fine. If not, thank goodness you’re over a sink!

Wait for the reaction to stop. I stir lightly with a stainless steel teaspoon to make sure everything is reacted. You should now have a black or nearly black liquid. If you’re not happy with the color, add a little more iron vinegar.

Now it’s possible the addition of the iron salts diluted the ink more than ideal. Just let it sit out a week and it will evaporate down to a nice concentration. You can test it with a brush, paper towel or even a finger (I’d use the pinkie because a good batch will stain skin for a couple days). If all has gone well, it should stain paper or your skin black like ink...which it is.

Once you're happy with the concentration, put it in a jar with a lid. I add a drop of grain alcohol for preservation out of habit from making tinctures. But it is possible with all the tannin no preservatives are needed. After all this work I’m just extra careful.

Now you have ink!

[samples]

Next: False Orpiment: how not to die of lead poisoning when following in the footsteps of artistic monks.