A surfactant is a compound that lowers the surface tension between a liquid (paint) and a solid (a miniature), acting as a wetting agent. Add a little to your paint water for two effects at once: it dissolves acrylic build-up on your brushes so they stop clogging and stay cleaner for longer, and it acts as a flow aid, making paint slide off the brush and onto your model rather than dragging, which is a real help for fine detail work.

A little surfactant in a wet palette helps keep mould at bay, especially when paired with demineralised water instead of ordinary tap water. Less smell, and the same flow-aid benefit carries over.

• Brush revival. Dilute roughly 50% with demineralised water and rub the brush in the palm of your hand to clean it and bring old, dead brushes back to life.
• Faster glazing (juicing). Speeds up layered glazes: the solvent evaporates quickly, leaving a streak-free glaze.
• Airbrush thinner substitute. Shares the same active ingredients as an airbrush thinner, so it works as a dilutant there too.