Walnut ink is made from the dark outer hulls that surround the walnut shell, not from the edible kernel. As the hulls steep and simmer, they release a rich brown colour that can be used at full strength for lettering or diluted with water for soft washes.
The process is simple, but a few details matter. The hulls need enough time in the water to release their colour, the liquid should be strained carefully, and the finished ink must be treated as a perishable, water-based material. A small batch is easier to control and less likely to spoil before it is used.
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What you will need
For a modest batch, gather:
- 100 g fresh walnut hulls, or about 50 g dried hulls
- 500 ml distilled water
- A stainless-steel saucepan reserved for craft use
- A wooden spoon or other stirring tool
- A fine sieve, muslin, or clean cotton cloth
- A heatproof bowl or jug
- A clean glass jar with a lid
- Gum arabic, if you want a slightly more flowing and cohesive drawing ink
- Gloves, an apron, and a washable work surface
Fresh hulls are soft and often green, yellow-green, or beginning to turn brown. Dried hulls are darker, lighter in weight, and generally more concentrated by weight. If collecting fresh walnuts, remove the outer hull from the hard shell and discard the shell itself. Chop the hulls into smaller pieces so that more of their surface is exposed to the water.
Walnut hulls stain skin, cloth, wood, and porous worktops readily. Use utensils that will not return to food preparation, and label the jar clearly. Do not taste the liquid or use it in anything intended for eating.
Preparing the hulls
Fresh hulls can be used as soon as they are removed from the shells. Brush away loose dirt and cut them into pieces roughly the size of a thumbnail. There is no need to wash them aggressively; excess water will only dilute the first stage of the extraction.
Dried hulls should be free of visible mould and unpleasant odours. If they are in large pieces, break or cut them before measuring. Dried material can be soaked before heating, which helps it soften and begin releasing colour evenly.
The quantities above are a starting point rather than a fixed formula. Hulls vary in age, moisture, and colour, so the strength of the final ink will vary too. Keeping the ratio reasonably consistent makes later batches easier to adjust.
How to make walnut ink
1. Soak the hulls
Place the prepared hulls in the stainless-steel saucepan and add the distilled water. Leave the mixture to soak for at least several hours, or overnight if convenient. This is especially useful for dried hulls. The water will begin to take on colour before heating, while the hulls soften and swell.
If you are working with fresh hulls, a shorter soak is sufficient, but an overnight rest will not harm the extraction. Cover the pan while it stands so that dust and debris cannot settle into it.
2. Simmer gently
Set the pan over low to medium heat and bring the mixture to a gentle simmer. Avoid a hard boil. Boiling is more aggressive than necessary and can cause the liquid to foam, evaporate too quickly, or catch on the bottom of the pan.
Simmer for 45 to 60 minutes, stirring occasionally with a wooden spoon. The hulls will soften and the water should become a deep brown. If the liquid reduces markedly before the hulls have softened, add a little more distilled water so that they remain mostly covered.
Keep the pan attended while it is on the heat. This is a small operation, but the dark liquid can disguise scorching at the bottom. A low, steady simmer is preferable to high heat.
3. Strain the first extraction
Set a fine sieve over a heatproof bowl or jug and pour the warm mixture through it. Press the hulls gently with the back of a spoon to recover liquid, but do not force large particles through the sieve. For a smoother ink, strain the liquid again through muslin or a clean cotton cloth.
Very fine sediment may settle later, even after careful straining. This is not unusual for a plant-based ink. If a clear working liquid is important, let the strained ink stand until sediment collects at the bottom, then pour the upper portion into another vessel without disturbing it.
Photo by Felix Mittermeier on Unsplash.
4. Concentrate the colour
Return the strained liquid to the clean saucepan and simmer it again, uncovered, until it reaches the strength you want. The time will depend on how much liquid remains and how dark the original extraction was. Stir from time to time and watch the level closely.
For broad brush washes, stop while the liquid is still relatively fluid. For lettering with a dip pen, reduce it further until the colour appears strong on a scrap of paper but still leaves the nib freely. Remember that the ink will look darker in the jar than it may appear once dry.
A useful approach is to remove a teaspoon of liquid at intervals and test it on scrap paper. Allow each mark to dry before judging it. Wet walnut ink can look warmer and darker than the dry line.
5. Add gum arabic, if desired
Gum arabic is optional. It can give the ink a little more body, help it sit on the paper, and make it better suited to some lettering work. It can also make the ink feel sticky or cause it to flow less freely if too much is added.
Dissolve a small amount separately in warm distilled water, then stir a little into the cooled ink. Begin cautiously rather than adding a large quantity at once. Test the mixture with a dip pen after each addition. If the line drags, forms heavy beads, or dries with a brittle surface, dilute it with a little distilled water.
For a loose wash, many makers prefer to leave gum arabic out. The plain extraction can be diluted directly with distilled water and applied with a brush.
Testing the finished ink
Test the ink on the same sort of paper you plan to use. Smooth, hard-sized paper will usually give a cleaner line, while absorbent paper may allow the ink to spread and appear paler. Try both a dip pen and a brush, since a mixture that behaves well for one may need adjusting for the other.
Load the dip pen lightly and draw a few lines at different speeds. The ink should leave a continuous mark without flooding the nib. If the line is too pale, reduce the ink a little further or use a fuller pen load. If it skips, thickens at the edges, or dries too slowly, dilute it by drops with distilled water.
With a brush, test a full-strength stroke beside one or two diluted washes. The colour should remain brown as it dries, though the exact tone may range from warm sepia to a cooler, nearly black brown depending on the hulls and concentration.
Photo by Ashkan Forouzani on Unsplash.
Storing walnut ink
Pour the finished ink into a clean glass jar while it is warm but no longer steaming. Leave a little space at the top and close the lid once the jar has cooled. Label it with the date and whether gum arabic was added.
Because this ink contains water and plant material, it can spoil. Store it in the refrigerator and use a clean tool each time. Watch for mould, gas, an unusual smell, or a texture that has changed significantly. If any of these appear, discard the ink rather than trying to rescue it. A small batch is sensible because the ink is easiest to use while fresh.
Do not store it in an unlabelled food container, and do not return unused ink from a working dish to the main jar. Keep the jar away from children and animals, and protect the refrigerator shelf from spills.
Common problems and simple adjustments
The ink is too pale. Simmer the strained liquid longer to reduce it. Testing a small sample after drying is more reliable than judging the colour while it is hot.
The ink is too thick. Add distilled water a few drops at a time and test again. Thick ink may also be carrying fine sediment, so allow it to settle and decant the clearer portion.
The pen clogs. Strain the ink again through a finer cloth and avoid adding more gum arabic. A dip pen should be rinsed in water soon after use and dried before storage.
The colour spreads on the paper. Try a smoother, better-sized sheet, or allow the ink to reduce slightly. Too much water in the mixture can also encourage feathering.
The ink dries unevenly. Stir or gently roll the jar before filling the pen, since natural particles and heavier colour may settle. For important work, strain the batch once more.
Making walnut ink is less about forcing a precise colour than learning how the hulls, water, heat, and paper affect one another. Once the first batch is dry on the page, its strength can be adjusted easily: reduce for depth, dilute for washes, and add only enough gum arabic to suit the tool in hand.