Wetting behaviour of single crystal alumina with gold and tin in an helium environment ( pO 2 = 10 −16 Pa) is investigated using the “laid-on droplet” method. In the case of gold (which has no affinity with oxygen), the temperature coefficient of contact angle, dθ dT , is experimentally shown to be negative and that of sticking work to be positive; both of them have very low absolute values. In the case of tin, the dependence of θ vs T is far more complicated due to the affinity of tin with oxygen: 1. (a) Between the melting point of Sn and T ∗ ( pO 2 = 10 −16 Pa, T ∗ = 1000K ), that is the range where SnO 2 oxide is thermodynamically stable, apparent contact angles are shown to have very high values ( θ ∼- 150°) and ( dθ dT ) ∼- 0 . In this domain, the existence of an oxide film on liquid Sn prevents the formation of a true metal-substrate interface. 2. (b)At T ∗ , the oxide film disappears by a dissolution process in liquid Sn and θ drops to ∼- 100°. Between T ∗ and ∼- 1450 K, a ( dθ dT > 0 behaviour is observed due to the surfaceactive effect of solute O 2 within the liquid, 3. (c) At T > 1450 K, the concentration of solute O 2 in Sn progressively decreases when T increases so that θ ∼- 125° and ( dθ dT ) < 0 are observed, which are the specific values for pure Sn. Experiments carried out in a vacuum environment allow the dependence of θ vs T plots on total and O 2 partial pressures to be characterised.