Wolfgang-
The stresses applied to ecsaine in piano actions are several.
On the knuckle there is a strong hammering stress, followed by drag in two directions. This contact is usually lubricated by dry lubricant.
On the backcheck there is a dragging force between the ecsaine and the wood hammer tail, not lubricated and intended to “jam” under the force of the hammer leaving the string.
What I find of interest is that ecsaine is available in several thicknesses and that its stiffness can be modified by sizing with different strengths of B-72 resin, and that layers of ecsaine can be laminated to produce different thicknesses, stiffnesses and surface textures. I’ve made so many varieties that I’ve lost track of what’s what, and so am limiting my report to one simple combination of soft ecsaine on top of stiffened ecsaine. This produces something which may be similar to peau de buffle. In any case, it gives the gentle effect I want on my lautenwerke.
Stiffer laminations give an effect similar to hard leather, but for that effect I’d rather use delrin.
I think I’ve made my limited claim that it’s worth investigating clear, and I look forward to possible reports from people who are better able to test, criticize and evaluate the materials.
Here’s a link to a short article about Ken Eschete which makes brief mention of his use of B-72 resin about half way through the article.< https://www.spokesman.com/stories/2021/jun/27/spokane-piano-restorer-touches-keys-of-history-fro/?fbclid=IwAR3rR9KPJgAPuYUymPM68vTaM7qs-9dNKgp6S88lYZiLCt8Cny4BG9DhG2o>