During the first half of the 18th century, the guitar lived quietly, but there were still people who loved the guitar quietly studying and transmitting. In Europe, the guitar is passed down in folklore and this is a great luck for the guitar. The structure has been added to make the guitar sound closer, not the academic elegance of the 17th century. quieter. The book by musician F. Moretti in 1799 tells about this.
Another person with the most credit to the guitar in 18 is Miguel Garcia. He has encouraged young musicians to compose guitar in many places. This is the generation that made the success of the guitar in the 19th century.
As for the guitar image gradually shifting to figure 8 with 6 single strings, no one has confirmed which country it is. Probably thanks to the flexibility of learning from each other. In the Spanish school, the monochord follows with the curved rod more than the number 8, while the German and Italian schools are a bit more square.