Crystallization pathways of BaOsingle bondCaO-Al₂O₃-SiO₂ (BCAS) glass were determined as a function of time and temperature, using a set of adapted and in-situ characterization techniques such as differential thermal analysis, high-temperature X-ray diffraction, nuclear magnetic resonance and high-temperature environmental scanning electron microscopy. Glass systems are a melted quenched bulk form and a deposited thin-film form (Pulsed Laser Deposition technique was used to obtain a coating on Si-substrate with a thickness up to 100 nm). The composition of the crystallized phases depends on the geometry of the glass, and of the applied geometrical constraints. These constraints control the volume fraction of crystallized glass melt as a function of time and temperature, and thus modify the reactional pathways.