In this paper explicit formulas, prescribing pressure difference limits, are reported in the case of ribbon growth by edge-defined film-fed growth method. These formulas were established in general for any growth configuration and for materials for which alpha(c)+alpha(g) < pi/2. The limits represent the boundaries of the ranges where the pressure difference value has to be chosen or can be chosen, in order to have a static and stable convex free surface. The advantage of this kind of formulas is that they can be used in the experiment or in the manufacturing technology design. (C) 2008 Elsevier B.V. All rights reserved.