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Background: The five basic preparations of Ayurveda, swarasa (expressed juice), kalka (paste), kwatha (decoction), hima (cold infusion) and phanta (hot infusion), are the foundation of most other dosage forms. Each represents a distinct extraction method, defined by solvent ratio, temperature and duration. Objective: To interpret the five preparations in terms of extraction science and to review the evidence on how their process variables affect composition, yield and quality. Methods: A critical narrative review of classical process descriptions and of pharmaceutical, analytical and quality studies of kwatha and related preparations. Results: The preparations form a graded series of aqueous extraction methods. Kwatha uses 4, 8 or 16 parts of water depending on the hardness of the drug, with boiling on mild heat (often cited as about 85–90 °C) until the volume is reduced to one-quarter or one-eighth; hima uses about six parts of water overnight at ambient temperature; phanta uses about four parts of hot water until cool. Studies show that water quantity, particle size, plant part and scale of manufacture alter composition, and that industrial steam-jacketed extraction can reduce processing time from 16–21 to about 6 hours with comparable yield. Commercial ready-to-use kwathas contain preservatives, sometimes at high levels, and can differ in phytochemical markers from freshly prepared decoctions. Conclusion: Panchavidha kashaya kalpana encodes rational extraction principles. Defining particle size, solvent ratio, temperature and end-point, together with marker-based standardisation, would make these preparations reproducible.