Last verified: April 2026
Shodhana — Purification of Minerals and Metals
Shodhana is the mandatory first step in every Rasa Shastra preparation — the purification of raw metals and minerals before any subsequent processing. Classical texts are unambiguous: unpurified materials are toxic and therapeutically ineffective; purification is not optional but foundational. The Shodhana process is documented with precision in Rasa Ratna Samucchaya and Rasa Tarangini — different processes for different substances, each described with the specific media, temperatures, and repetitions required.
Shodhana for key substances
Multiple trituration stages
Mercury is the most complex Shodhana process. Classical texts document: first washing with Triphala decoction; then repeated trituration (Bhavana) with specific herb juices (typically Kumari/Aloe vera svarasa, Neem leaf juice, Triphala — each for 3–7 days); then specific fire processing stages. Modern understanding: the Bhavana process with herb juices creates organo-mercury complexes and then reduces free mercury through sulphur binding in Kajjali formation. The classical Parada Shodhana specifically targets the Naga (lead) and Vanga (tin) impurities naturally occurring in cinnabar ore.
Quenching in herbal decoctions
Iron is heated to red-hot in fire and then quenched (plunged) into specific herbal decoctions or liquid media — typically Triphala decoction, sesame oil, and cow's urine in rotation. This is repeated 7–21 times. Modern interpretation: the quenching cycle produces surface oxidation and converts free iron to iron oxide forms — Loha Shodhana produces a mixture of iron oxides that are more bioavailable and less irritating to GI mucosa than elemental iron.
Melting and straining through milk
Sulfur is heated until molten and poured through a cloth into cold milk — the milk's proteins bind organic impurities. Repeated 7 times. The purified sulfur is used directly in compound preparations and is the 'Shuddha Gandhaka' specified in all compound formulations.
Heating and quenching in sour media
Copper is heated to red-hot and quenched in sour plant juices (buttermilk, lime juice, sesame oil). The acidity dissolves verdigris (copper acetate — the primary toxic impurity on copper surfaces) while the heat-quench cycle prepares the copper for Marana.