In industry seeding is successfully used to initiate crystallization. In melt crystallization seeding can be used to initiate the crystallization with the aim of separation of one compound at a desired undercooling within a molten mixture. In combination of such a separation by melt crystallization with a drop forming process a self-controlled (in situ) coating process is in principle possible. In the case just mentioned it is necessary to clarify the influence of seeding on the separation, since seed crystals are being located at the surface of the pastilles. To evaluate the influence of the seeding a model system of polyethylene glycol (PEG) 6000 and benzoic acid was used. Cross section microscopy images were used to show the penetration depth of PEG 6000 seed crystals within the outer pastille layer. A mathematical estimation of the seeding influence (on the impurity concentration within the outer pastille layer) compared with measured values shows, that the seeding itself does not decrease the impurity concentration in the outer layer obviously. (C) 2015 Elsevier Ltd. All rights reserved.