Abstract: Using the contact angle technique and a series of alkanes as probe liquids to wet the surface of Norway spruce resin (Picea abies L. Karst.), the critical surface tension of this resin was measured to be about 18.48 mN/m. Using Hamaker’s extrapolation method for critical surface tension, a good linear relationship was found by plotting Hamaker constant of the liquid with cos θ. This method was thus developed to obtain the unique critical Hamaker constant for this resin to be about 4.18×10-20 J.