I made this (together with several other designs, both millefiori and lampwork) on a week long course with Willie Manson in 2003. I think the clarity of the glass depends upon the quality of the glass and eveness of temperature, and Willie seemed to have no problems with cording. I think he still runs some Masterclasses from time to time, as does John Deacons. Everyone who goes on these courses comes back with some passable weights, and learns a lot about the processes - and some of the challenges! Well worthwhile if you have the time.