Aluminium alloys DC-cast ingots are widely used as flat rolled products in building, construction and automotive applications. Some of these applications necessitate a very uniform, high quality surface appearance, which is closely related to the original as-cast microstructure. Inhomogeneity in the cast microstructure, for example floating crystals, negatively impacts the surface quality of the final products. In this study, the casting process parameters, which could potentially result in the formation of floating crystals, were assessed. Metal level, casting speed, melt temperature and metal distribution are the main casting parameters which can be correlated with the presence of free floating crystals. These parameters must be properly adjusted in order to obtain a homogeneous grain structure.