Making Ultramarine from Lapis Lazuli — Extracting the Most Precious Pigment in History

Start with 50-100 g of lapis lazuli stone. Choose pieces with the most vivid blue and least white calcite. Crush into small fragments with a hammer, then grind to a fine powder in a stone mortar and pestle — the finer the grind, the better the extraction. The powder will be a dull, greyish-blue at this stage because of the calcite and other impurities mixed with the lazurite. This grinding takes 30-60 minutes of hard work. The powder should pass through a fine mesh sieve.

Melt together 60 g of pine resin, 30 g of beeswax, and 30 g of linseed oil in a pot over low heat. Stir until fully combined into a smooth, sticky mass. This is the 'pasta' — the sticky matrix that will trap the impurities while releasing the blue lazurite. The proportions can vary but the resin must dominate — it provides the stickiness that holds the calcite and grey minerals. Let the mixture cool until it is warm but still soft enough to knead — roughly 40-50°C.

While the paste is still warm and pliable, work the ground lapis lazuli powder into it. Knead thoroughly for 10-15 minutes until the blue powder is uniformly distributed throughout the sticky mass. The paste will turn a dull blue-grey. Shape it into a ball. Let the paste rest for 3 days at room temperature — this 'resting' period allows the resin to fully penetrate the mineral particles and bond with the calcite and impurities, making the separation more effective.

Prepare a solution of warm water (40°C) with 10 g of sodium carbonate (soda ash) per litre — a mild alkaline solution that helps release the blue particles. Place the rested paste ball in a large bowl and pour over the warm alkaline water. Begin kneading the paste under the water — squeeze, fold, press. The water will turn vivid blue as lazurite particles wash out of the paste while the white calcite and grey minerals remain trapped in the sticky resin matrix. Continue kneading for 10-15 minutes until the water is deeply coloured.

Pour the blue water into a clean glass container, being careful to leave the paste behind. This first extraction contains the finest, most vivid ultramarine — 'ultramarino fino'. Let the blue water stand undisturbed for several hours or overnight. The blue pigment will settle to the bottom. Pour off the clear water above. The sediment is pure ultramarine pigment. Repeat the kneading with fresh warm alkaline water 2-3 more times — each extraction yields a paler grade. The second wash is 'secondi' (good quality), the third is 'ceneri' (ash-blue, still usable).

Pour off the last of the clear water from each settled grade. Spread the wet pigment on a clean glass surface to dry completely. The finest grade will be a vivid, deep blue — the true ultramarine that medieval painters prized above all other pigments. The second grade is a lighter, still beautiful blue. The third grade is pale but useful for skies and light areas. Store each grade separately in sealed glass jars. Natural ultramarine is lightfast, chemically stable, and compatible with all binders. From 100 g of good-quality lapis lazuli, expect 10-25 g of combined ultramarine pigment.