Linothorax vs Quilted linen vs spolas

[John Conyard]

I'm very interested in the reference to shoe making.

spolas: khitoniskos bathus skutinos; ho bursinos thorax

]little thick leathern chiton; the leathern thorax"
(skutinos= animal skin generally; bursinos = dressed leather, or alum tawed - the root is connected to shoemaking)

Why is shoe making connected to alum tawed leather? Would not other tanning methods be more appropriate for shoe making? Am I missing something here? If it has something to do with shoe making are we not just looking at vegetable tanned leather?

I've spent a two days in a vegetable tanned thick leather tube and yoke. The pteruges ensured I couldn't sit down. Too stiff. I suspect they would soften with time. Perhaps.