The wetting of refractory substrates by oxide alloys has been investigated using a high-temperature sessile drop bench. The aim of this study was to select the best crucible material for directional solidification processes such as the Bridgman, edge-defined film-fed growth or micro-pulling down methods. Contact angles and surface tension were determined via high-resolution imaging. The O-2 partial pressure in the furnace atmosphere was also measured. Alumina and a eutectic ceramic called A/YAG/Z (Al2O3/Y3Al5O12/ZrO2) were studied by investigating the following systems: alumina/molybdenum, alumina/tungsten and alumina/iridium; A/YAG/Z-molybdenum, A/YAG/Z-tungsten and A/YAG/Z-iridium. The results show intermediate wetting for both oxides (30A degrees A < theta < 50A degrees). This is an original result for A/YAG/Z. Several previous studies reported good wetting (7A degrees A < theta < 20A degrees) for alumina. Accurate surface tension values could not be obtained by image processing. Therefore, the Wilhelmy method was used, giving gamma = 0.63 +/- A 0.03 N m(-1) for alumina, which is comparable to the value of 0.67 +/- A 0.03 N m(-1) reported in the literature. The surface tension obtained for A/YAG/Z was 0.71 N m(-1), but this value was influenced by the approximate density used. A metal-like layer was observed on the apex of the drops after solidification. According to an SEM-EDS analysis, most of these layers were composed of molybdenum, tungsten and oxygen. Based on thermodynamic calculations, a mechanism which takes into account the oxidation of Mo parts and the dissolution of oxides in the drop is proposed.