The origin of the elementary entities which have been previously revealed on float glass fracture surfaces have been investigated. Fractography experiments were carried out on a borosilicate demixed glass and glass-ceramics with well-defined submicron heterogeneities. The fracture surfaces exhibit entities with lateral dimensions in agreement with the size of the demixed zones and of the crystallites, respectively. Furthermore, it is shown that the pinning/depinning models, which describe the crack front as a moving line possibly pinned by heterogeneities, may apply in the sub-critical regime of the fracture of glass. The roughness properties of float glass fracture surfaces are quantitatively analyzed in the framework of self-affine geometry.
