Kirza, the material used to make Soviet boots, is widely regarding as having been a critical material for the Russian war effort, both saving soldier's feet from trench rot and saving billions of rubles from genuine leather construction of older styles of boots.
However, when looking into it more in depth, it seems it's almost a mystery as to how it is made. Wikipedia simply says it was multiple layers of textile (no mention as to what kind of textile, how many layers, etc), " modified by membrane-like substances " which is even less descriptive.
I'm curious if someone has sources for this material in English, how it was made, what it was made of, what the 'membrane-like substance' was... basically, if I were planning on making a patch of Kirza for my own personal satisfaction, where would I go to find more information on it?
A bonus question: Was Kirza really so critical to the Russian war effort? What was used before? What was used after? Why was it ultimately replaced in the 1970/80's?
Any help is greatly appreciated.
Edit:
I found a few sources that were somewhat helpful in at least narrowing down what was used, if not a specific method of manufacture. Shared below, hopefully it helps someone else scratching their head about needlessly secretive Soviet boot factories.
https://textiletrend.ru/pro-tkani/raznyiy-sostav/kirza.html
https://elementy.ru/nauchno-populyarnaya_biblioteka/431941/Kirza
https://rg.ru/2019/10/07/rodina-legendy-kirzaci.html
The exact details of the manufacture of kirza were a closely guarded industrial secret, as you might imagine. It's a composite made of multiple layers of fabric sandwiched between layers of rubber or a synthetic rubber substitute like styrene-butadiene or polyisoprene.
In this way, kirza is less a fake leather than a type of cloth made waterproof with a layer of polymer.
You may find the comments of this LanguageHat post from 2008 to be a useful source for further explanation: languagehat.com/kirzakersey/
All further sources I have attempted to find on this subject are in Russian or Polish, neither of which are languages I can read.