Making Chalk White Pigment (Whiting) — Grinding and Levigating Natural Chalk

Start with a lump of natural chalk (calcium carbonate). Break it into walnut-sized pieces using a hammer or by hand — chalk is soft enough to crumble easily. Remove any flint inclusions, dark streaks, or clay contamination. The purest chalk is brilliant white throughout with no discolouration. About 200 g of raw chalk will produce approximately 150 g of finished whiting after losses from levigation.

Crush the chalk pieces in a mortar and pestle until reduced to a coarse powder — roughly the texture of granulated sugar. Chalk is very soft (Mohs hardness 1-3) and grinds easily. Work in batches if the mortar is small. The goal is to break down the lumps enough for levigation — the water will do the final sorting.

Place the crushed chalk in a large jar or bucket and add 1 litre of clean water. Stir vigorously for 2 minutes to suspend the particles. Let stand for exactly 30 seconds — the coarsest particles will settle to the bottom. Carefully pour the still-cloudy suspension into a second clean container, leaving the settled grit behind. This milky suspension contains the finest chalk particles — the pigment-grade whiting. Repeat the stirring and pouring with the settled residue to extract more fine particles.

Let the milky suspension stand undisturbed overnight (8-12 hours). The fine chalk particles will settle to the bottom as a dense white layer. The water above will become clear. Carefully pour off the clear water without disturbing the sediment. The settled white mass is your whiting — pure, fine-grained calcium carbonate pigment.

Spread the wet whiting paste on a clean, non-absorbent surface (glass, ceramic, or plastic) in a thin layer and let it dry completely in a warm, dry place. This takes 1-2 days depending on temperature and humidity. Once dry, break up any cakes and grind briefly with a mortar and pestle to restore the powder. The finished whiting is a brilliant white, silky-smooth powder. Store in a sealed jar. Use as a white pigment, a filler in gesso and putty, a base for distemper paint, or a polishing compound.