Argentifaction - making silver
Argentifaction – Making silver
When Andrew and I selected recipes for this series of experiments, we favoured recipes that appeared simple. Method 14 for making silver made the cut because it was short and featured only a few ingredients: copper, brass, bronze, arsenic sulfide, and silver. Nothing too fancy.
Then again, the previous recipe, for imitating gold, taught us that appearances can be deceptive. There, the proportional amounts of ingredients given in the recipe did not furnish us with the desired results. We also needed to tinker with the sequence and added techniques for aiding amalgamation. We also did separate batches with materials that had undergone “purification” (śodhana) and that hadn’t. In our new recipe, we could apply some of the insights we developed in recreating the last recipe.
This is the fourteenth method for making silver given in the eleventh chapter of the Rasaprakāśasudhākara.
तालं ताम्रं रीतिघोषं समांशं कुर्यादेवं गालितं ढालितं हि /
अम्ले वर्गे सप्तवारं प्रढाल्य पश्चाद्योज्यं तुल्यभागे च रूप्ये /
शुद्धं रूप्यं षोडशाख्यंहि सम्यक् जातं दृष्टं नानृतं सत्यमेतत् // १२३ //
Prepare equal amounts of arsenic sulfide, copper, brass and bronze. Melt and quench them in the sour group of substances seven times. Having poured this into an equal amount of silver and amalgamating it with it, it properly becomes pure silver, known as “sixteen-(coloured)”. This has been observed, it is not false, it is true. (Rasaprakāśasudhākara 11.123)
This recipe for argentifaction - making silver (not faking, or argentifiction!) is presented as one that the author of the Rasaprakāśasudhākara had experience with. Notably, actual silver is the main ingredient, by prescribed amount at least. This made recreating the recipe a somewhat unnerving undertaking, as silver prices are currently quite high. We used about £140 worth of silver for this recipe.
Andrew started preparations for the recipe long before we actually tackled it, partly because several of the recipes we chose for our experiments feature the same ingredients, and partly because he wanted to have everything ready for all the different recipes once we started. Now, however, we are both a bit confused as to what he did exactly. But here goes:
The argentifaction recipe doesn’t make mention of any of the ingredients needing to be purified before use. However, we still had leftover purified copper from the previous recipe. And Andrew had brass and bronze in stock, both previously purified, and had prepared standard size ingots of the brass, bronze, and copper. Andrew also applied a purification procedure to the arsenic sulfide.
Rasaprakāśasudhākara, chapter 6, verse 4 gives the following instructions for purifying arsenic sulfide:
कुष्माण्डतोयसंस्विन्नं ततः क्षारजलेन वा /
चूर्णतोयेन वा स्विन्नंदोलायन्त्रेण शुध्यति //४//
Then, [arsenic sulfide] becomes pure after it has been steamed with wax gourd water, or with alkaline water, or with lime (calcium oxide) water in a swing-apparatus.
Andrew used wax gourd decoction, as he still had some wax gourd from the coral recipe, where it was used for the purification of cinnabar.
[Orpiment, or arsenic sulfide, before purification]
[Purification: cut a wax gourd into pieces and boil in water. Use the decoction for the steaming process in the swing-device (dolāyantra). The orpiment pieces are placed into a cloth, and the bolus is hung into the wax gourd decoction and boiled for ca three hours. It is considered purified afterwards]
However, we didn’t purify the silver, for no other reason than that I forgot to send Andrew any instructions. That is, back in February, I had found instructions for purifying silver in the Rasaprakāśasudhākara (chapter 4, verses 24-26) and had discovered, on cursory reading, that it involved a somewhat complicated process of smelting silver with ferric sulfate and lead. This seemed excessive. And also, the silver to be purified was identified as “being conjoined with copper, etc., impure, mixed, and flawed” (tāmrādisaṃsargabhavaṃ tvaśuddhaṃ rūpyaṃ hi miśraṃ khalu doṣalaṃ ca), which our silver didn’t seem to be. But mostly, I just forgot.
Here, though we didn’t use any, is a picture of ferric sulfate, just because it is pretty!
Back to the recipe for making silver: Once all the materials were assembled, it was indeed fairly straightforward.
Step one: Melt equal amounts of copper, and bronze.
Step two: Add brass and melt.
Step three: Add arsenic sulfide.
Step four: Quench the alloy in “sour substances” – we went with fermented rice water.
Step five: Remelt and quench – six more times.
Step six: Remelt and cast ingot.
Step seven: Melt equal amounts of the alloy and silver and cast.
Step eight: Polish. And polish some more.
[Unfortunately no pictures of the pouring of the liquid metals into the sour gruel for quenching, but you can see the results here. The bronze-copper-brass alloy amalgamated very well, as the sawn piece shows. After seven quenchings and recasting the alloy, it was melted again, together with the silver]
Voilà, pure silver! Actually, sixteen(-coloured) silver, according to the text. Which seems to simply mean pure silver. I could not find a definition of this term in the alchemical works. However, Dr Parth Kale (a trained ayurvedic doctor who had done some parallel experiments to ours in the past) explained that the term refers to the colour left by rubbing gold or silver on a scratch plate or touchstone. Pure gold or pure silver would be streaked across the plate leaving a gold or silver trail. The sample to be tested would be scratched next to it and the colours compared. The colours would vary depending on how much of another metal had been added. The standard weight for gold or silver was one tola (~ 10g), which equals sixteen māṣa (1 māṣa ~ 625 mg). One tola would therefore be sixteen parts pure gold. Adding other metals would then make fifteen-part gold, or fourteen-part gold, etc., depending on the amount added.
And here they are: our "pure silver" ingots. Not too bad after polishing.
The recipe stated that the copper-brass-bronze-arsenic sulfide alloy and the silver should have equal portions. However, we found that if you used a little less silver, the result would actually be a bit more like silver!
For this recipe, our main takeaway is that we still needed to tweak the proportional amounts a little. The casting went very well, even without using jequirity beans to hinder oxidation. However, we lost a lot of material, probably in the quenching (you can see how the sour gruel looks after several quenchings in the picture above). The loss of material was substantial: We started with 110g of each material, but after processing only about 225 g were left over. A reduction by half, in other words! And only doubling the amount of silver, as it were, instead of a five-fold increase.
This was an expensive recipe to recreate. Perhaps it would have been less expensive for alchemists in India in the past, if most of the materials were locally available. Copper, for example, is now very expensive. But it may have been something alchemists were able to gather (mine?) themselves.
The recipe reminded me of stretching a soup by adding water - here, silver is stretched by adding the other metals. These would perhaps also counter some of the less desirable traits of silver, such as its tarnishing through oxidation. Several days after casting, the ingots have not started to tarnish. The arsenic sulfide may have brightened the colour and at the same time hardened the metal. Orpiment or arsenic sulfide is a difficult material to use, as it is poisonous. One must avoid skin contact and breathing in the fumes. It is, however, a fairly ubiquitous material in both Ayurveda and in Rasashastra.
Would this stretched material have been acceptable to traders in India in the sixteenth century? This would perhaps depend on the mentioned scratch test. (Note to Andrew: we should get a touchstone!)
Andrew applied a series of tests to our alchemical silver:
Certainly, no modern-day jeweller would be fooled. But perhaps it's not a question of fooling someone, but rather that a material fulfills its purpose. If it looks like silver and acts like silver in the needed ways, then it counts as silver!
Indeed, the Rasaprakāśasudhākara knows three categories of silver:
Mined silver (khanijam), natural silver (sahajam), and artificial silver (kṛtrimam) (see RPS 4. 21-23). Mined silver is dug out from the earth, whereas natural silver is said to be found on the top of Mount Kailasa. Artificial silver is produced from tin (vaṅga) through "piercing with mercury" (rasavedhena). Our silver recipe uses neither mercury, nor tin (unless we count the tin that is a constituent of bronze). Nevertheless, the author understands it as real silver, pure silver even, not something that is merely "like silver".
Here is the film of the procedure.