for example laundry detergents are designed to promote a high contact angle or even complete detachment for an oil droplet on a surface, facilitating disproportionation and roll-up; antifoams depend on the partial wettability of hydrophobic particles to cause film breakage; in a Pickering emulsion, particles with a judiciously chosen contact angle sit on the interface and stabilise oil droplets; and in mineral flotation, differential wettability is used to separate the valuable ore from the unwanted 'gangue' components. 17