You now need to separate the stems into two kinds of fibre. With a twisting, sliding motion, you can remove the stringy outer bast fibres from the more woody core.
Before they can be made into a sheet, the fibres need beating. Beating is a mechanical process that "frays" individual fibres, whilst at the same time separating them from the bulk stem and softening them. This allows them to both spread out more evenly in the sheet, and to touch more fibres in the sheet. When the sheet is formed, it is contact between individual fibres (just the contact, not any tangling) that gives the sheet strength.
It is at this point that a dedicated, professional papermaker would turn to his Hollander beater
and process the whole batch in four hours of continuous beating.
Most normal humans do not have their own Hollander (they cost a few thousand dollars), so use either a blender or mallets. Mallet method.
This is something I had never tried, because I have never dealt with such amazingly long fibres as those in the nettle.
The method originates in Japan, where papermaking is undertaken with a spiritual, almost religious reverence. Japanese papermaking materials and processes are quite different to the westernised methods I am describing here. If you are interested, the terms to use when googling are washi, kozo, tororo
and mulberry bark
A thick mixture of the stems are beaten with flat-faced wooden mallets on a hard, usually stone, surface. To separate the fibres, a hit-and-drag method is used - as the mallet hits the fibres, it is also pulled towards the papermaker so that friction rubs the fibres apart. Every few minutes, the papermaker pauses to pick through the fibres to lift out loose specks of bark or discoloured fibre.
The beating goes on for quite some time, often hours.
I did not have mallets, nor did I have a stone working-surface.
I did, however, have a lump of wood and an old cheeseboard clamped to my portable workbench.
The method did work, but proved to be amazingly noisy, and tough on the hands (I wore gloves, but it was still a square lump of wood I was holding, not a rounded handle). Bits of stem flew hither and yon, and eventually I was firmly advised
by Kitewife to pack in making such a noise. To be honest, I could have done with wearing ear defenders.
With practice, mallets, and a bench made of paving slabs, I could probably get this method to work, but for now I had to resort to the kitchen blender...