I've read and seen videos saying that leather didn't actually exist as armor. If this is true, I presume this is just referring to the tanned soft leather that we know of today?
I've read about armor made of rawhide (untreated or partially treated) or boiled/hardened leather. Rawhide is supposedly cheaper to produce (as it doesn't require tanning) and is much harder (and rigid) and stronger than leather. I've read that the Qin lamellar plates were supposed to be lacquered and/or partially treated rawhide? I've also read that tanned leather has to be boiled (in water or wax) to produce a rigid shape (cuir bouilli) to create armor. So was regular soft leather not actually used as armor?
Can someone give me more information/details about pros/cons of rawhide vs soft leather vs hardened/boiled leather?
Rawhide resists penetration better for a given weight, compared to conventional tanned leather, boiled leather, and boiled rawhide. Tanning and boiling partly break down the material, making it weaker.
If your rawhide is too thin, you can either (a) use multiple layers, as seen in Japanese lamellar armour, Medieval rawhide helmets, and more, or (b) heat thicken it, which is a possibility for Medieval cuir bouilli, and was used for North American shields.
The best single source of data comparing these materials is Edward Cheshire's PhD thesis, Non-metallic armour prior to the First World War, The University of Reading, 2010: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.529983
The merit index Cheshire uses, (penetration depth)/density, doesn't work as a merit index. Using penetration*density as a merit index (low numbers are good), normalising to unboiled rawhide, the data in Cheshire's Appendices H & I gives
| material | merit index |
|---|---|
| rawhide | 1 |
| boiled rawhide | 1.21 |
| faced | 0.62 |
| horn | 0.30 |
| leather | 1.99 |
| boiled leather | 4.36 |
Boiled rawhide is only a little weaker. It's possible that more gentle heating would provide thickening while weakening it less.
But leather armour certainly existed, and was common at times: the buff coat. These are oil-tanned leather, not the same as our modern everyday tanned leather. It would be interesting to see good data for the protectiveness of buff coats. AFAIK, there is not yet any published.
Another armour material is half-tanned leather. Basically, rawhide in the middle, with the outside part tanned. The outside layer helps protect the rawhide, and the inner rawhide core provides strength and stiffness. It's a good material for knife scabbards.
There's a discussion of leather armour in https://www.reddit.com/r/AskHistorians/comments/7ohyw2/whats_wrong_with_leather_armor/ where u/Hergrim and I discussed a bunch of stuff, including Cheshire's results, and various sources that will be good further reading.