Making Watercolour Paint from Raw Pigments — Gum Arabic Binder

Gum arabic is the dried, hardened sap of the Acacia senegal tree, harvested primarily in the Sahel region of Africa (Sudan, Chad, Senegal). It dissolves in warm water to form a thick, sticky solution that acts as the binder and adhesive in watercolour paint. Measure 50g of gum arabic powder or crushed crystals into a heat-resistant container. Add 100ml of distilled water (a 1:2 ratio by weight). Stir and let it soak for at least 2 hours (overnight is ideal) — the gum needs time to fully hydrate and dissolve. If needed, warm the mixture gently (do not boil — boiling degrades the gum) and stir until smooth and honey-like in consistency. Strain the solution through a fine mesh strainer or cheesecloth to remove any undissolved lumps or impurities. The strained gum arabic solution is your base binder.

To the strained gum arabic solution, add approximately 10ml of glycerin and 5ml of honey. Stir thoroughly until both are completely incorporated. Glycerin is a hygroscopic humectant — it attracts and retains moisture from the air, which keeps the dried paint film slightly flexible and easily rewettable with water. Without glycerin, the dried paint would be brittle and crack in the pan. Honey serves a similar purpose and additionally acts as a plasticizer, giving the paint a smoother, more buttery consistency. Too much glycerin or honey makes the paint sticky and never fully dries in the pan; too little makes it crack and resist rewetting. The proportions above (roughly 1:5 glycerin-to-gum, 1:10 honey-to-gum by volume) are a reliable starting point.

Add 2-3 drops of ox gall liquid (a traditional wetting agent made from bovine bile — available from art suppliers) or, as a modern substitute, a single tiny drop of mild dish soap. The wetting agent reduces the surface tension of the paint, allowing it to flow more smoothly from the brush onto the paper and to spread evenly rather than beading up. This is especially important for heavily sized watercolour papers. Only a tiny amount is needed — too much wetting agent causes the paint to spread uncontrollably and lose the ability to form crisp edges. Stir gently to incorporate without creating bubbles. Your watercolour medium is now complete and ready for pigment dispersion.

Wearing a dust mask, place a small mound of dry pigment (1-2 teaspoons) on the glass slab. Add enough watercolour medium to create a workable paste — start with roughly equal volumes of pigment and medium. Using the glass muller, grind in circular motions just as with oil paint, dispersing the pigment evenly into the binder. Watercolour grinding is generally faster than oil paint because the gum arabic solution is thinner and more fluid than drying oil. Grind until the mixture is smooth, creamy, and free of visible gritty particles. Different pigments require different amounts of medium: high oil-absorption pigments like ultramarine also absorb more gum arabic solution, while dense pigments like yellow ochre need less. Adjust the ratio so the paint flows smoothly from a brush but is not watery-thin.

Using a palette knife or a small spoon, transfer the ground paint into empty half-pan shells (the small rectangular plastic or ceramic wells used in watercolour palettes). Fill each pan to the brim — the paint will shrink significantly as the water evaporates during drying. Let the pans dry in a dust-free location at room temperature. Drying takes 3-7 days depending on pigment, layer thickness, and humidity. As the paint dries, it shrinks and may crack or develop a concave surface — this is normal. Once the first layer is fully dry, refill the pan to the brim again with more paint. Most half-pans need 3-4 fill-and-dry cycles to build up a sufficient depth of paint. After the final fill is dry, the paint is ready for use. Rewet with a damp brush — the gum arabic redissolves and the paint behaves exactly like commercial watercolour.

Test each colour on watercolour paper. Wet the dried pan with a brush, pick up colour, and paint a graduated wash (dark to light). A well-made watercolour should rewet easily with just a damp brush (not requiring vigorous scrubbing), produce a smooth wash with no graininess, and dry to a uniform matte finish on the paper. If the paint is hard to rewet: add more glycerin to the formula for the next batch. If it is sticky and never fully sets in the pan: reduce the glycerin and honey. If the wash is grainy or streaky: the pigment needs more grinding. If the colour lifts too easily when overpainting: the gum arabic concentration is too low (add more gum to the medium). Keep notes on each pigment's behaviour — you will refine the formula with experience, because each pigment has different characteristics.