Since 2001 the authors have been involved with the archaeologists of the Fondazioni Lerici, Politecnico di Milano, in the preservation of some Hindu temples in Mỹ Sơn, Vietnam. The characterisation of the brick- masonry materials was carried out at the Politecnico di Milano. Especially interesting was the successful study of the natural resin used to bond externally the bricks in the masonry; this allowed the formulation of a new compatible resin to be used for the conservation project. In the masonry internal leaf, the joint material, based on clay, was substituted by a new hydrated lime and powdered bricks mortar. The results of the research presented here allowed the direct application of the new materials in the conservation project of G1, G3, and G5 of group G.