Adsorption of colloidal particles to an interface is of fundamental interest in understanding wetting, capillarity and colloidal forces as well as being of practical importance in formation of 'Pickering' emulsions. We propose to study concentrated latex/air interfaces in which the size and interactions of the particles are carefully controled. Refllection and off-specular scattering will allow determination of density normal to the surface as well as in-plane structure.