With a ribbon of wire, however, which is incredibly thin, and can almost be thought of as a unit of molecules on the same plane (which they obviously are not if you examine it at that level), the molecules on the outer portion of the bend don't have to stretch as much, and don't break apart much if at all. Think of the comparison between the ribbon of wire and the circular cross section of wire as the difference between a board and a dowell, or the difference between a flat piece of steel stock and a round rod of steel. The flat piece bends more easily.

Now if you take this ribbon and wind it in a helix with fibres in the middle to hold the shape of the helix, this allows even more flexing of the ribbon, and allows the unit of ribbon and fibre to be flexed in unlimited directions which a flat ribbon may not otherwise want to be flexed in (say flexed in the direction of the ribbon's width).

Tinsel wire is rather difficult to solder, but it can be soldered. Sometimes burning away the fibres helps, but then you have to remove the soot from the copper.

An interesting thing you can do with a strand of tinsel wire is connect about an inch or two across a medium current train transformer (say 4 amperes at 12 to 18 volts). It causes quite a flash because of the burning of the fibres.

Thomas