Obviously alchemical ideas and practise had to be communicated between people, by word of mouth or writing. But we are lacking in information about a lot of the information transfer in the past and exactly how it happened. This is a big, sprawling topic that I didn’t really cover in my book (http://www.newcurioshop.com/alchemy-medieval-tudor-england/),
so I am attempting to summarise some of my thoughts about it now.
Concentrating on Europe, and England, the earliest transmission was by learned men travelling to Spain and Sicily, to translate or copy alchemical and other related works on things like astrology and natural philosophy. They then returned home with a copy or two, or the copies were given as gifts to places of learning, or they went home and mentioned alchemy and such in their writings at home. The latter occurred with information about the four elements, as the translator Daniel Morley, who had copied and translated works abroad, being asked to write about this knowledge when he returned home to England in the 12/13th century. The books in places of learning were then copied by other visiting monks/ copied and given as gifts/ read by visitors who made their own notes, and thus the information filtered northwards.
Naturally this meant a very slow rate of transmission. It wasn’t until the 13th century and Roger Bacon before we really have much talk about Alchemy in England, but even then there’s not really much evidence of anything until the 1310’s and 1320’s, when it started to get rather busy and crops up in various circumstances, from legal records to an archaeological find in Cambridge.
But Bacon got his information from copies of only a handful of texts, perhaps picked up when he was in Paris. Bacon’s sources were, according to the article by William Newman on him in “Roger Bacon and the Sciences – commemorative Essays”, edited by Hackett:
an alchemical work attributed to ar-Razi, called the Lumen Luminum, another false work attributed to Avicenna called the Liber de Anima, as well as of course the Secreta Secretorum of pseudo-Aristotle.
He was basically working from texts, apparently with no transmission of secrets and ideas and practise in any other way. Moreover they were Arabic texts, translated into Latin and passed about between learned men and copied until Bacon made his own copies or purchased ones from people. In fact in his Opus Tertium he claimed to have spent “…more than 2,000 livres in these pursuits on occult books and various experiments and languages and instruments, and tables and other things.” (From page 119 of the Dover paperback of Holmyard’s “Alchemy”)
The 1330’s were also an interesting time with regards to other alchemical authors with the writing of The Testamentum of Raymond Lull, a pseudo-Lullian treatise, an early version of which claims to have been written in St Katherine’s, London, England in 1332. Unfortunately this was written in Catalan, so whilst the work itself may have been written at the time and place claimed, it didn’t have any effect on English alchemy, and the earliest mention of Lull as an alchemist is apparently from the 2nd half of the 14th century, according to Michela Pereira. Moreover he didn’t really appear in English alchemy until the 15th century, when we find a translation from Catalan into Latin or English taking place. So here we have a possible occurrence of a roundabout route of works, hampered by the use of a minority language (Catalan), and the importance of a universal language, i.e. Latin.
Later on, you can see that the audience for alchemical works and numbers of alchemists that we have record of greatly increases as the texts are translated into the local language in the 15th century and more people can read and write. The Semita Recta was translated into English, French and German from Latin in the 15th century, and many of these copies have survived. People passed it around interested parties who then made their own copy or had one made for them. There is evidence for a circle of alchemically interested intellectuals and doctors in 1440’s England, related to the Semita Recta and various pseudo-Albert of Magnus works. They would likely meet and discuss alchemical matters when possible, and pass on manuscripts or copies of them to each other.
I see no reason to doubt that similar things were happening all across Europe, with educated men, both professional and mere servants and artisans, learning about alchemy from each other and what works they found.
George Ripley, the famous 15th century English Alchemist, allegedly travelled abroad in order to learn more about alchemy and other topics, and by the 16th century we have various learned men writing about collecting books from the continent themselves, or their friends are asked to pick up what books they can find. Of course this was also the age of printing, and of a wider community of letters that was different from the earlier one in the 13th century.
Jennifer Rampling has written a paper (Available here: https://www.academia.edu/4760830/Transmission_and_Transmutation_George_Ripley_and_the_Place_of_English_Alchemy_in_Early_Modern_Europe) about how John Dee and Edward Kelly, in their peregrinations about Bohemia and Eastern Europe, spread knowledge of the works of George Ripley, which in turn were used by the alchemists in the late 16th/ early 17th century in their own writings and were also printed in books.
Another issue in consideration of alchemical knowledge transfer is that of transmission from master to pupil. If that was all that happened, then that would mean that alchemy was a rather different subject than what we think of it as being today. (I wrote a blog post on this 18 months ago: https://distillatio.wordpress.com/2014/08/04/is-there-much-evidence-for-direct-master-pupil-transmission-of-alchemical-knowledge-in-the-13th-to-16th-centuries-and-how-much-did-initiation-matter-versus-learning-from-books/)
However that clearly was not all that happened, although we have several claims about it taking place from the 15th and 16th centuries in England. But perhaps because it was seen as a Donum Dei, a gift of God, the alchemist could learn from books (After all, the Bible was a book too) and ultimately it was God that would give him the knowledge to make the stone. Also the idea was abroad in the later medieval period that it was legitimate to interrogate God’s creation to find out better how it worked, and as such, learning how do transmutation from books and by experimentation was entirely okay.
What I do wonder about is how useful alchemy was as a marker for being well educated, which could open some doors for your career, and also as a means of rubbing along well with people of other nationalities. There was to some extent still a pan-European feudal society, with people of the appropriate status mingling easily with each other and having languages and habits in common. Of course by the 16th century that had fragmented with the rise of nationalism and the reformation. I suspect though that it proves more useful in that regard in the 17th century, with the appearance of Rosicrucianism.
Certainly religion was important; it turns out that an Irish humanist called Richard Stanihurst (1547-1618) graduated from Oxford, and began alchemical studies in London, but he was a Catholic and left England, working in the Bishopric of Liege, where he was involved in the Paracelsian movement, and he ended up at the court of King Philip II of Spain. I doubt he would have been permitted to attempt to cure various diseases using alchemical methods if he was a Protestant and probably would not have left London. What seems clear from the summary of his life in the summary of Azogue no. 4, is the importance of groups of alchemists/ chymists/ medical men for passing knowledge and practises and supporting research. Stanihurst would surely have had a much harder time of it without support from the likes of the Bishop of Liege and others in the same area. As with the dissemination of Ripleyian alchemy, patronage is an essential part of the travels made by knowledgeable people and dissemination of their works. Unfortunately the issue is that the evidence for earlier ones, such as in the 13th century, just has not survived.
So, to summarise it – alchemical knowledge travelled with people as they travelled, and by written texts as they were traded and given and received. It was retarded by language problems, and by distance, and made easier by patronage from the rich and powerful.