There Is Leather, and There Is Leather

I've purchased four cheap Chinese mechanical watches lately that have all come on virtually identical black, crocodile-grain leather straps. All are stamped identically, "Genuine Leather." If I compare them to a similar Hamilton strap—most certainly genuine leather—they are much more glossy and in other obvious ways dissimilar to it. And if I compare them to a junk croco-grain vinyl strap, all are similarly slick and glossy on the croc side. But otherwise, the "Genuine Leather" straps seem in comparison to indeed be sort of leather. To confuse things more, some listings call them "PU leather." Huh?

L-R: Genuine top-grain Hamilton croco-grain strap; a PU (or, bycast) leather croco-grain strap; and a vinyl croco-grain strap. (Now that is a boring picture.)

Turns out there are degrees of leatherness. My Hamilton strap, on both its front and back sides, is some version of top grain leather. Top grain is just what it sounds like, leather taken from the outside top (hair side) of a leather hide. It's the outside of the hide that contains the grain, "the pores, wrinkles and other characteristics which constitute the natural texture of the leather." Most top grain leather has been sanded down to remove blemishes and "corrected" through dying and imprinting a new grain, like the croc grain of my Hamilton strap. But even though it is heavily corrected, this top grain strap quickly started breaking in, conforming to my wrist, and developing some patina on the wrist side.

But tanners can make a hide go much further by splitting it horizontally, which may be done as many as four times. So split leather is the "lower (inner or flesh side) layers of a hide that have been split away from the upper, or grain, layers." Split leather of course has no grain and is not as tough as top grain. It is often napped and used as suede.

PU leather, more commonly called bicast/bycast in the West, is split leather that has been bonded with a surface layer of polyurethane, into which may be molded a grain like (here) crocodile. So PU or bycast leather is just plastic with a leather backing. This is why my PU leather and my vinyl straps are almost identical on the outside. Some countries do not even permit manufacturers to label bycast as leather.

So in the UK, New Zealand and elsewhere, my PU (bycast) leather straps cannot legally be marked "Genuine Leather." Bycast leather is better seen as an imitation leather that contains leather byproducts. Bycast is very inexpensive, as little as $1.00 per square meter. If you own a cheap leather chair, it is almost certainly bycast. Same for Payless-grade leather dress shoes, etc. I would not say bycast is evil, but my bycast straps are only minimally wearable. They look and feel plastic because they mostly are plastic. In shoe terms, they are most certainly Payless specials.