Technical ceramics for high-performance applications can be additively manufactured using vat photopolymerization technology. This technology faces two main challenges: increasing ceramic product size and improving product quality. The integration of process control strategies into AM equipment is expected to play a key role in tackling these challenges. This work demonstrates the feasibility of real-time and in-situ feedback control of the light-initiated polymerization reaction that lies at the core of vat photopolymerization technology. To prove the principle, a single-layer experimental setup was developed in which the degree of conversion was measured by infrared spectroscopy. Experimental data obtained from this setup was used to develop a control-oriented process model and identify its parameters. A material perturbation was applied by adding an inhibitor and the case with and without feedback control were compared. The results show that the feedback controller successfully compensated for the material perturbation and reached the same final conversion value as the unperturbed case. This result can be considered a fundamental step towards additive manufacturing of defect-free ceramic parts using in-line process control.