"Bob's my cat" fired this volley in news:31665795-
:

I believe the "filigree process" is biological, i.e. rotting,

'tis. The leaves are fermented in an airtight damp press, similar to the
Cavendish process for tobacco. Then they are layed out damp on a slightly
resilient surface and "pounced" with a sparse-but-stiff bristle brush to
remove the membranes between the veins, similar to how you'd do stenciling.

After careful drying - again in a press - they're painted or plated as
desired.

LLoyd