Art, Recipe, writing

Walnut Hull Ink

If you live with Black Walnut Trees, you know all about the way the hulls stain your fingers when you try to reach the elusive but delicious nuts inside that baseball sized green hull. If you think about it, anything that stains can be used as a dye – or an ink. As a chemist by day, artist by night, the chemistry of dyes has long been of interest to me, and when I started thinking about making my own ink for this Inktober, I wanted to dig into the chemistry behind the color.

Walnuts emit an allelopathic toxin which is, in essence, their own homegrown herbicide. The idea behind this is that it keeps competition for light, water, and nutrients down in the immediate area of the tree. The way they do this is by production of hydrojuglone, which turns to juglone on exposure to air once leaving the tree. Juglone is also the active ingredient in the dye or ink we can create from the hulls of the walnut. Juglone binds to fibers, more quickly in the presence of heat, but in ink we cannot necessarily or practically heat our pages while we write or draw.

There are a number of recipes out there for walnut ink, and the first thing I realized is: this is an easy and cheap (if you have ready access to the trees) ink to create. So easy, you may find yourself with far too much on hand! However, the instructions are sometimes vague, and I wanted to experiment myself with different methods.

This, then, is the first method for the ink. The other will take some time (more time than I had for this first batch) and I will write up later.

Walnut Hull Ink

  • Hulls or whole nuts from the Black Walnut
  • Water to cover

And yes, that is all currently. Some recipes call for adding alcohol, as you will see, I’m not so sure this is a good idea, even if I wind up having to refrigerate the ink to retard mold growth.

Black walnuts collected from my yard

In a stainless steel pot, I placed the hulls, then added water to cover (or at least to top of nuts.) They float, so you will want to kind of hold them down to judge where this is. Place the pot on the stove on high, bring to boil for one hour.

I like the smell of black walnuts, but wasn’t sure what boiling them would be like. I don’t have an outdoor burner, so this was my option… and it was fine. Not stinky at all. 

Cool. Strain through cheesecloth, or a coffee filter.


Here’s where I started to play with the recipe and methods a little. I took the first filtrate yield, and diluted it with 10% alcohol (I used 91% isopropyl alcohol) and bottled it.

The alcohol makes the ink bleed a lot. I won’t use it again. 

I kept some of the filtered ink in an open beaker, then put it in a water bath (my crockpot, on low) overnight. This is the ink in the test labeled evaporated.

Improvised water bath! I put water in to the level of the ink in the beaker. 

Some of the ink did not want to pass through the filter, so I poured it into a small jam jar, careful not to pour in the sludge that was choking the filter (or at least not too much of it) and this is the test swatch labeled unfiltered.

Day 1 of Inktober 2019, the unfiltered ink. The drawing is still wet, here. This was done with glass dip pen on watercolor paper. 

Since I had made such a large batch, I left some steeping in the pot after pouring off the first amount to filter. This is the swatch labeled ‘steeped’ and this was day three of steeping. I will test again over several days of this brew, and it is only partly covered, so there will be some evaporation as well.


The swatches were done on watercolor paper with a sable paintbrush. I will come back later to check for color fading, but historically walnut dyes and inks are noted to be colorfast, so I don’t expect much. I will also continue to write up this ink, as well as the pokeberry ink I also made.

Happy Inking!

15 thoughts on “Walnut Hull Ink

  1. Question?

    Does the person sticking his/her foot in the mushroom circle think something will grab him/her? 😀

  2. Does walnut ink have enough corrosive elements to damage paper and nibs? I recall seeing old manuscripts where the letters were letter-shaped holes. Does walnut ink need a mordant, or is it “self-biting”.

    1. I suspect the ‘letter shaped holes’ were from Oak Gall ink, which is both tannic, heavily iron mordanted. I’ll keep an eye on this ink for a while to see what I get. I’m not using a mordant. You can, and some recipes call for it, but I wanted to approach it first without any mordant for simplicity’s sake.

  3. Fascinating – and potentially useful next time I need to write a low-tech civilization, especially the bit about crystals for portability. One question: do you have any feeling for how the ink holds up over time? I’m extrapolating from some long-ago experiments with vegetable dyes, when I discovered that a lot of the pretty colors I could get had no staying power. Without the appropriate mordant they washed right out, and even with a mordant they faded quickly if exposed to air or light.

    1. I’m going to be monitoring for colorfastness. I didn’t use any mordant in this batch, or the first pokeberry batch. I think this will last well – I’m more dubious about the pokeberry. I’m going to try goldenrod blossoms with an alum mordant next. I did some natural dying years ago and am working partly from a book I bought back then. I want to try bindweed for green.

      1. Pokeberry was one of my total failures, though maybe I didn’t use the right mordants – this was a long long time ago, before natural dying became a Thing, and I had to get my chemicals by begging from pharmacists and chemistry teachers. It was quite a disappointment – the berries and juice are such a pretty color.

        Blackberries were another failure. Though I did accidentally make blackberry wine by leaving a solution outdoors in the summer.

  4. I’ll vouch for the herbicide nature of walnuts. I had to take down a black walnut tree that had been pruned but with no wound care. Beetles got in, and the tree had to come down.

    A few years after that, I was growing tomatoes in the back yard. They did fine, except for the plants within 30 feet of the old stump. (Look up walnut-wilt for the details).

    The next year, gophers were waiting for me to plant. They got all the tomatoes, and a few dwarf trees.

  5. Saw a recommendation to use a bit of salt and vinegar to inhibit mold. Another was to add a few rusty nails for darker color (simulating oak gall ink).

    Also seems to me you could just smash, soak, and let drain and dry without the bother and nuisance of boiling and straining.

    BTW be careful with black walnuts; juglone can be toxic at a level similar to cyanide, and the mold that decomposes the hulls releases a neurotoxin.

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