This paper discusses the effect of intentional deformation of a flexible formwork after casting of the concrete and the influence of the characteristics of concrete in the fresh state on the quality of a concrete element. This deformation is intended to bring the concrete element in its desired final shape; the deformation typically takes place in the first hour after casting. In this research thin double-curved precast shell or cladding elements are considered. The paper introduces the method used to support the flexible formwork and focuses on the concrete technology necessary to control the process of deformation after casting. Relevant parameters are discussed that influence the concrete’s behaviour shortly after casting. Rheological characteristics of the fresh concrete appear to be particularly important for the design of a suitable mixture. Since from traditional concrete research little experimental data on deformation after casting appeared to be available, experiments were carried out to test a number of prepositions. Results of these experiments are shown as well.