"A white coating’s opacity derives from some light absorption but predominantly light scattering, which is a function of differences in refractive index between paint components. In conventional white decorative coatings, for example, the main contribution to scattering is the difference in refractive index between titanium dioxide pigment (n=2.7) and the continuous medium, the resin system (n≈1.5). Titanium dioxide has one of the highest refractive indices known, and is certainly the most widely used white pigment, but in recent years the price of titanium dioxide has increased rapidly and there will be serious supply shortages in the foreseeable future.At the same time, there is a growing awareness of sustainability and environmental issues in the chemical industry and particularly the coatings industry, and methodologies, such as life cycle analysis and carbon footprints, are being developed to quantify the ‘environmental friendliness’ of coatings’ materials and products. Titanium dioxide pigment is one of the major contributors to a coating’s carbon footprint and the manufacturing process for titanium dioxide produces unwanted waste products.Another way of enhancing opacity in a white coating is the inclusion of air (n=1), which can improve the efficiency of titanium dioxide as an opacifier, air has environmental and cost benefits. The DRYFOAM project will develop novel opaque architectural coatings, based on a foam structure. It aims to develop stable and tough foam scaffolds within coatings, particularly for ceilings and interior walls, capable of withstanding normal wear and tear conditions. The European interior wall coatings market (including ceilings) was estimated in 2008 as 2.79 million tonnes (valued at €4.65 BN), more or less equally split between the professional decorating and the home (DIY) decorating market."