Electron energy loss spectroscopy (EELS) is used to study the transition from the buffer layer to the first graphene layers during graphitization of SiC(0001). Graphene growth is controlled and correlated with spot profile analysis in low energy electron diffraction and x-ray photoelectron spectroscopy. In the EELS data both electronic transitions and plasmon losses are sensitive to the interface. The collective in-plane excitations show a characteristic blueshift upon graphitization, while single electron transitions with dipole moments along the surface normal are suppressed for the buffer layer. These dependencies can be used to control the number of epitaxially grown graphene layers. © 2009 American Institute of Physics.