Background: Kupipakwa Rasayana is a specialized pharmaceutical technique of Rasashastra in which mercury–sulphur formulations are processed within a sealed glass bottle under controlled heating. Rasa Sindhura is a classical Kupipakwa Rasayana widely used for its Rasayana and Vyadhihara properties. Traditionally, this preparation is carried out using Valuka Yantra with graded Agni, whereas modern pharmaceutical practice increasingly employs a muffle furnace for better control and reproducibility. Objective: To document and compare the traditional and modern methods of Kupipakwa Rasayana preparation, correlating classical Agni concepts with temperature-controlled muffle furnace methodology. Materials and Methods: Rasa Sindhura was prepared using Śuddha Pārada and Śuddha Gandhaka following classical Kajjali preparation. Traditional heating was conceptualized through Agni Lakṣaṇa, while the modern method employed a muffle furnace with gradual temperature increments. Observations during various stages of heating were recorded and correlated. Results: Classical Agni stages—Mṛidu, Madhyama, and Tīvra—could be systematically correlated with specific temperature ranges in the muffle furnace. The pharmaceutical characteristics, deposition pattern, and organoleptic features of Rasa Sindhura were comparable in both methods. Conclusion: The muffle furnace method offers a standardized and reproducible approach to Kupipakwa Rasayana preparation while preserving the core Rasa shastra principles. Integration of traditional concepts with modern technology enhances pharmaceutical safety, precision, and academic validation.