Lane, Alan, Ewan Campbell, and J. Bayley. 2000. Dunadd: an early Dalriadic capital. Oxford: Oxbow Books.
Archaeological publishing is very expensive, and tends to produce thick books that are too obscure for a wide audience. The authors managed to produce a very informative and readable book about their excavations in 1980-81 at Dunadd, Scotland, by including the most significant findings and lots of images. Then in addition, there is a digital archive of the full technical details. Separate pdfs describe the contexts, phases, and finds, along with other interesting analysis and catalogues. This archive is available from ADS, as well as the University of Glasgow. Section 2.1, the finds information, includes this description of the most interesting and challenging bead out of the 14 found.
1963 Barrel-shaped bead of ‘herring-bone’ blue and white pattern. The bead is exceptionally well made with 11-12 rows of blue and white twisted cable in alternating bands. Made by winding a joined cable of S- and Z-twist cables five or six times round and marvering in. The core is of the same blue glass but plain. The blue glass is a translucent blue and the white is opaque, but not densely so. Many bubbles. Central perforation D. 3.5 mm., Ht. 9 mm., D. 9 mm. Site 1 (45B) SF1032. – pg. 124
I have limited lampwork experience, but the part that was the most difficult for me is in twisting an alternate direction. I learned how to make nice, tiny, twisted bi-color stringers. But twisting the other direction, which would be needed to create the joined cable of S- and Z-twist is unnatural and a lot of mental effort.