Making Zinc White Pigment — The Non-Toxic Replacement for Lead White

Obtain metallic zinc — either as commercial zinc ingots or zinc sheet offcuts. You need approximately 200-300 g of clean zinc metal. Zinc has a relatively low melting point (420°C) and boils at 907°C — both well within reach of a charcoal furnace or propane kiln. Cut or break the zinc into small pieces (1-2 cm) so it melts and vaporises faster. Remove any galvanised coatings or surface contamination — you want pure zinc metal. Historically, zinc was smelted from calamine (zinc carbonate) or sphalerite (zinc sulfide) ore, but for pigment-making, start with refined zinc metal.

The French process requires heating zinc to boiling point and collecting the oxide. Set up a small charcoal furnace or kiln with a refractory crucible. Above the crucible, arrange a sheet-metal collection hood or chimney lined with cotton cloth screens where the zinc oxide fumes will deposit. The key principle: zinc boils at 907°C, the vapour rises and immediately reacts with oxygen in the air (2Zn + O₂ → 2ZnO), forming an extremely fine white powder that floats upward and settles on any cool surface. Work outdoors or in a very well-ventilated workshop — zinc oxide fumes are not seriously toxic but can cause 'zinc fever' (metal fume fever) if inhaled in quantity.

Place the zinc pieces in the crucible and bring the furnace to full heat. The zinc will melt first (at 420°C), forming a shimmering liquid pool. Continue heating — as the temperature approaches 907°C, the zinc begins to boil vigorously, producing a dense white smoke of zinc oxide. This white smoke rises from the crucible and deposits on the collection surfaces above. The reaction is self-sustaining once started — each zinc atom that vaporises immediately oxidises in the air. Continue until all the zinc has vaporised. From 300 g of zinc metal, expect approximately 350-370 g of zinc oxide (the oxygen adds mass). The deposited powder is extremely fine and fluffy — a pure, brilliant white.

Once the furnace has cooled completely, carefully scrape the white zinc oxide deposit from the collection surfaces. The powder is already extremely fine — far finer than most ground mineral pigments — but grind lightly on a glass slab with a muller to break up any clumps. The pigment should feel silky-smooth and impossibly light. Zinc white has a characteristic cool, slightly blue-white colour — noticeably different from the warm ivory-white of lead white or the dead white of titanium dioxide. This cool undertone is prized by painters for mixing clean, bright tints.

For watercolour (Chinese White): grind zinc white with gum arabic and a drop of glycerine — the glycerine prevents the watercolour cake from cracking. For oil painting: grind with linseed or walnut oil on the glass slab. Note that zinc white in oil dries very slowly and forms a brittle film — professional oil painters traditionally mixed it with a small proportion of lead white for better handling. For tempera: mix the dry pigment with egg yolk medium. Zinc white is permanent, non-toxic, and does not yellow — making it ideal for white passages in watercolour and for tinting other colours. Store dry pigment in airtight jars away from moisture.