Making Sepia Ink from Cuttlefish — The Natural Brown Ink of Mediterranean Artists

Obtain a fresh cuttlefish from a fishmonger or fish market. The ink sac is a small, silvery-black, pear-shaped organ located in the body cavity near the head, between the gills. Carefully cut open the mantle (body) along one side and locate the ink sac — it is fragile, so handle gently. Remove the sac intact by cutting the small duct that connects it to the siphon. One large cuttlefish yields approximately 2-5 ml of liquid ink. For larger quantities, collect sacs from several cuttlefish. You can also use squid ink sacs, though these are smaller. Place the intact sacs in a clean bowl.

Carefully puncture each ink sac over a clean glass jar and squeeze out the liquid ink. The raw ink is a thick, very dark brown-black liquid with a faint marine smell. Rinse the emptied sacs with a small amount of clean water to extract remaining ink. The total volume from 10 cuttlefish sacs should be approximately 20-50 ml of concentrated ink. If you can obtain pre-extracted cuttlefish ink (sold by some fishmongers and specialty food suppliers), this step can be simplified — the commercial product is identical.

Pour the collected liquid ink into a shallow ceramic dish and place in a warm, dry, well-ventilated area away from direct sunlight. The ink slowly dries over 5-7 days to a hard, brittle, very dark brown-black cake or crust. This drying concentrates the melanin pigment and removes the water and volatile components. The dried sepia cake can be stored indefinitely in this form — it does not degrade. Historically, sepia was traded in dried cake form across the Mediterranean. Once fully dry, the cake should be hard and brittle, snapping cleanly when broken.

Break the dried sepia cake into small pieces and grind to a fine powder in a mortar. To prepare usable ink, dissolve the powder in warm water — start with approximately 1 part sepia powder to 10 parts water, and adjust the concentration to taste. More powder gives a darker, more intense brown; more dilution gives pale, golden washes. Add a small amount of gum arabic (approximately 5% by weight of the dissolved ink) as a binder — this gives the ink body, improves flow from a pen, and helps it adhere to paper. Stir thoroughly until completely dissolved.

Store the reconstituted sepia ink in a tightly sealed dark glass jar. The ink keeps well for weeks in liquid form, though it may develop a slight marine smell over time — adding a drop of clove oil prevents mould growth. Sepia ink is a superb drawing and wash medium: it flows beautifully from a quill or reed pen, produces warm, transparent washes when diluted, and has a natural tonal range from pale cream-brown to deep chocolate. Unlike iron gall ink (which eats into paper over centuries), sepia is gentle on paper and does not corrode. For watercolour washes, dilute further with water. Store extra dried sepia cake in a sealed jar — it keeps indefinitely and can be reconstituted at any time.