UV curing plays an important role in the optical shop for cementing optics or for the fabrication of replicated optics. Material shrinkage is a common but unwanted effect during UV curing, because it causes stress and form modifications. In order to minimize these effects it is useful to measure shrinkage and surface changes that occur during the UV curing process. For replicated optics, shrinkage and form modifications are usually measured by comparing the replica to the mould geometry after the curing process has finished. In this paper, a measuring method is presented, which enables the observation of shrinkage and changes of the surface shape in situ. The surface of UV hardening material, in this case a commercially available optical adhesive, is monitored interferometrically during UV curing. This enables observing the material effects that cause stress and form modifications in real time.