Titanite consists of TiO6 octahedra arranged in chains. These are linked by SiO4 tetrahedra. At room temperature, Ti is slightly off-center resulting in an alternation of short and long Ti-O bonds. The displacement direction is reversed between neighbouring chains making it antiferroelectric at room temperature. A phase transition occurs near 500 K where the Ti is centering in the octahedra on average. X-ray diffuse scattering indicates that 2D short-range correlations develop above Tc characterised by streaks. We have obtained data at room temperature from a unique large high-quality crystal at 300 K and observed diffuse scattering throughout reciprocal space. A model has been developed that reproduces the diffuse scattering. We would like to map the diffuse scattering at 500 K and model in detail the origin of the diffuse streaks. Therefore we ask for 4 days of beamtime on SXD.