This paper is the first part of a serie of two papers dealing with bulking: a quasiorder on cellular automata comparing space-time diagrams up to some rescaling. Bulking is a generalization of grouping taking into account universality phenomena, giving rise to a maximal equivalence class. In the present paper, we discuss the proper components of grouping and study the most general extensions. We identify the most general space-time transforms and give an axiomatization of bulking quasiorder. Finally, we study some properties of intrinsically universal cellular automata obtained by comparing grouping to bulking.