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Background: Kupipakva rasayanas are prepared by heating a kajjali-based charge in a clay-coated glass bottle (kupi) embedded in a sand bath (valuka yantra) or furnace, so that the product sublimes to the neck or collects at the base. They include some of the most important mercurial and stannic preparations of Rasa Shastra. Objective: To review the process parameters and analytical characterisation of kupipakva rasayanas, and to identify critical control points for standardisation. Methods: A critical narrative review of standard manufacturing procedure and pharmaceutico-analytical studies of Rasasindura, Makaradhwaja, Svarna vanga, Rajata, Tamra and Malla sindura, together with studies on their composition and safety. Results: Studies converge on a three-stage heating programme: mild (mridu, up to about 250 °C), moderate (madhyama, about 250–450 °C) and intense (tivra, about 450–650 °C or higher), lasting from about 10 to more than 36 hours, with corking of the bottle after sulphur fumes subside. Yields vary widely, from about 39% for Tamra sindura to 76–94% for Makaradhwaja, depending on the charge and the form of the added metal. Rasasindura is red trigonal mercuric sulphide (cinnabar) formed by sublimation of the black cubic sulphide in kajjali. In Makaradhwaja, gold content ranged from 19 to 268 ppm depending on whether gold foil, leaf or bhasma was used. Electric muffle furnaces have replaced sand baths in several studies. Conclusion: Kupipakva preparation is a reproducible sublimation process when temperature-time programmes are controlled. Defined heating profiles, phase identification and assay of mercury and added metals should form the basis of monographs.