The subject of the paper is heat exchange in the system casting - riser - ambient. The examinations were focused on evaluating temperature dependence of the coefficient of heat exchange from open (not shielded) top surface of riser to ambient. The examinations were carried out on the open surface of cast steel riser, of temperatures 1000-1500°C. On the basis of the performed examinations it was stated that heat emission coefficient changes its mean values by about 50% during feeding process of the mild steel casting, i.e. from about 0.28 in liquid state to about 0.42 at temperatures close to solidus. This wide range of surface heat emissivity changes should be taken into account when boundary conditions are formulated in elaborated models of solidification and in designing risering systems.
 A. Gradowski, W. Krajewsk i, Determining Selected Parameters which Describe Cooling Kinetics ofa Riser Top Surface, Proceedings of the IXth Scientific Symposium of Faculty of Foundry, Academy of Mining and Metallurgy, Krakow 1983, pp. 27-35 (in Polish).
 P.K. Krajewski, G. Piwowarski, W.K. Krajew - ski, Determining Temperature Dependencies of Sand Mould Thermal Properties, Proceedings of the 6th International Conference on Solidification and Gravity, Miskolc, Hungary, 2013.
 P.K. Krajewski, G. Piwowarski, J.S. Such y, Formulating the boundary conditions for numerical model of heat transfer inasystem heat source - heat sink. Thermal conductivity of the system, Proceedings of the Workshop ”90 Years of Educating Foundry Engineers by the AGH University of Science and Technology in Krakow”, AGH University of Science and Technology, Faculty of Foundry Engineering, Krakow, 2012.
 W.K. Krajewski, J.S. Suchy, Determining of the accumulating plate material Thermal Properties of Insulating Sleeves, Materials Science Forum 649, 487-491 (2010).
 W. Krajewski, Investigation of the High-Aluminium Zinc Alloys Grain Refinement Process due to Ti Addition, Archives of Metallurgy 44, 51-64 (1999).
 W.K. Krajewski, A.L. Greer, A.L. EBSD Study of Zn Al25 Alloy Inoculated with Zn Ti4 Master Alloy, Materials Science Forum 508, 281-286 (2006).
 W.K. Krajewski, J. Bura s, M. Zurakowski, A.L. Gree r, Structure and properties of grain-refined Al-20 wt.% Zn sand cast alloy, Archives of Metallurgy and Materials 54, 329-334 (2009).
 K. Haberl, W.K. Krajewsk i, P. Schumacher, Microstructural features of the grain-refined sand cast Al Zn20 alloy, Archives of Metallurgy and Materials 55, 837-841 (2010).
 W.K. Krajewski, A.L. Gree r, P.K. Krajewski, Trends in the development of high-aluminium zinc alloys of stable structure and properties, Archives of Metallurgy and Materials 58, 859-861 (2013).
 P.K. Krajewski, Z. Zovko- Brodarac, W.K. Kra- jewsk i, Heat Exchange in the System Mould - Riser - Ambient. Part I: Heat exchange coefficient from mould external surface, Archives of Metallurgy and Materials 58, 847-849 (2013).
 The Engineering Tool Box, Air properties, http://www.engineeringtoolbox.com, 2013.
 Table of emissivity of various surfaces, Micron Vertretung Schweitz, Micron Instrument Company, Inc., www.transmetra.ch, 2013.