As I understand, Japan was quite a big source of silver at the time, so consideration of getting concessions from Japan, a weaker power than China at the time, would probably have looked easier, no?
Japanese Silver
Mexican silver accounted for some $560 million or roughly 84% of global production in the period 1790-1829 CE, with most of the remaining production coming from Argentine, Chile, and Russia. Lin, in China Upside Down (2006) states bluntly that China could no longer obtain silver from Japan during this period, though they do not specify whether this was the result of low production, strict Japanese government controls, or because China had a small trade deficit with Japan throughout the late-eighteenth and nineteenth century.
China had lost most sources of Asian silver around this time. Imports of silver from the Ryukyus ended in 1715, those from Burma ended when Chinese-operated mines were plundered and abandoned in 1758-59, Chinese silver mines in Annam were shut down in 1775 due to pressure from the Annamese government, and domestic production in Yunnan declined by about two-thirds between 1790 and 1829.
But again, Silver production in the Americas dwarfed these sources, and an estimated 27% of all global silver was ending up in China during this time. I would be curious what evidence has led you to believe that Japan was a large-scale silver producer during this period, as my understanding is the Japanese silver production peaked in the seventeenth century
Silver, Tea, Silk, and Opium
The trade of silver for tea, silk, & porcelain; and the purported lack of Chinese demand for foreign goods, is the conventional narrative going back to Fairbanks in the 1950s, but it has been subject to substantial revision, with the elements you are asking about being seriously challenged from the late 1990s on. To my knowledge, a definitive replacement narrative is yet to emerge. The older narrative is heavily dependent on sources such as Morse (1926) which only looked at the British East India Company (EIC) records which end in 1833. The Fairbanks narrative isn’t really plausible when you start considering the records of China’s trade with other countries or the massive volume of trade conducted by China’s own merchants and ships. Silver was certainly valued, as it had been the dominant monetary medium for certain crucial government functions since the sixteenth century. Silver was required for sufficient monetization of China’s growing population and economy, as the Chinese share of global GDP grew from 22% in 1700 to an estimated 33% in 1820, while the population roughly doubled during the same period. But China also imported large amounts of many products, the preference for silver within the Canton System doesn't really characterize the bulk of China's commerce.
This narrative also largely ignores the complexity of the Chinese currency system during this period. Promissory notes, Qianpiao, Silver bullion, silver specie (coins), and copper coinage were all in use. Silver and copper coins had independent values and fluctuating exchange rates within the country, with copper coinage a government monopoly, silver values largely set by the market and silver bullion privately minted. This complexity was further compounded by widely different rates of exchange and currency valuation across different Chinese provinces.
Von Glahn in ‘Fountain of Fortune’(1996) or more succinctly Flynn & Giraldez “Cycles of Silver” (2002) argued that silver importation largely stemmed from higher prices for silver in China. This theory does helpfully emphasize that silver is not just currency or a unit of exchange, but also a product in its own right. Although the arbitrage impact is large during the periods 1540-1640 and again during 1700-1750, this revisionist theory it is less useful for explaining silver outflows from China in the early nineteenth century, and I think this revisionist line goes too far in discounting the global demand for Tea and Silks.
Lin (2006) similarly rejected the simplistic Fairbanks narrative. Highlighting that the period after 1850 saw huge silver inflows into China while Opium imports also doubled, which contradicts any simple relationship between silver and Opium. Min also notes that the earlier period of silver exports (1826-1850) by British merchants coincided with a global downturn in tea and silk exports.
Irigoin (2009 and 2013) explores an interesting dimension of this, arguing that the brief period of British silver exports from China was influenced by the overvaluation of the Carolus (Spanish silver dollar, ‘piece of eight’) which was coinage taken at face value, versus Silver Liang/ bullion/sycee which was valued according to silver content. Carolus production was interrupted by South American independence movements, and subsequent coinage was heavily debased for a period of several decades. Merchants within China largely rejected the new South American coinage after debasement began, causing the rapid appreciation of the limited stock of Carolus. A stock which was steadily reduced due to the common practice of re-minting specie into bullion. This created unequal demand for different types of silver within China, which did not resolve meaningfully until debasement was ended and the Mexican Peso gained widespread accepted around 1850 similar to the Carolus. The Carolus during the early-nineteenth century was valued 5-25% higher than its silver value, or even more in some places. This potentially created the opportunity for arbitrage profits in the opposite direction, and hence Silver bullion shipments to India by British merchants, even as American merchants continued to ship large amounts of silver coinage into the country. Irigoin concludes that “it is difficult to blame Opium for de-silverization” agreeing with Lin but for different reasons.
Most of the scholarship I have discussed deals with slightly different time-frames and data-sets. As far as I know, there has not been any definitive scholarship which reconciles trade date for Chinese merchants, the resurgence of paper money in the early 19th century, changing demand for bullion and specie, and the changes in silver-copper exchange rates to give a holistic narrative of China’s currency situation in the leadup to the Opium War.
However, you state that “British merchants resorted to opium trade with China due to lack of silver needed for the exchange” and I can say this is likely not the case. Opium instead presented British merchants with better margins than trading silver, and this overall dynamic was shaped by various other factors: increasing demand for opium within China, differing Chinese demand for non-Carolus forms of silver, and a temporary downturn in international demand for tea and silk. The 25 year period where China had a net outflow of silver was followed by several decades during which China’s Opium imports doubled while silver inflows far exceeded the outflow during the previous period.
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