We present a fully general derivation of the Laplace--Young formula and discuss the interplay between the intrinsic surface geometry and the extrinsic one ensuing from the immersion of the surface in the ordinary euclidean three-dimensional space. We
prove that the (reversible) work done in a general surface deformation can be expressed in terms of the surface stress tensor and the variation of the intrinsic surface metric.
We show how it is possible to define and compute the potential between $q$ and $bar q$ external sources in the singlet and octet (adjoint) representation of the colour group.
