Material Matters: Leather Part 2
Date: October 26 2016
By: Adam Jane
Last time on MM we looked at the process that turns animal skins into leather – known as tanning. Once the tanning process is done and we have our leather there’s still plenty of work to do. After the liquid tanning process the leather will be pressed to squeeze out excess liquid, then checked over again for any defects. With the tick of approval from tanner the leather can now be coloured and finished. There are a few different ways to colour leather these days, but the primary methods are dyeing and staining.
Dyeing and Staining
To dye the hides they’re placed a big rotating tub with either a natural or a synthetic dye. Natural dyes can come from all manner of odd places, and have been used to colour textiles since the Stone Age. Natural dyes include pigments extracted from berries, bark, leaves, beetles, sea snails, roots and even certain minerals in mud – people were pretty imaginative back in the day. Synthetic dyes have been in use since the mid 19th century and nowadays have become the industry standard, as they allow a greater range of colours, they work faster and tend to be more colourfast than organic alternatives. Staining merely requires the dye to be applied to the surface of the leather. Traditionally this would have been done with a brush but is made much easier with modern spraying machines. The hides are then dried out completely, ready for finishing.
Full Grain Leather
At this point, the leather’s true fate will be decided. In its simplest form the leather can be left as it is, as what we call full grain leather. As we mentioned last time, leather starts off quite thick, with tighter, more densely packed fibres on the outside and looser, longer fibred through to the flesh side. On full grain leather the texture of the skin side will be left on top. Full grain leather tends to be the toughest option, as well as the most expensive, but some people find the natural finish to be a bit too rough. Full grain leather can be as much as 5mm thick, so as hard-wearing as it may be it’s generally a bit too bulky for use on sneakers. (Although not always) More often than not the leather on our sneakers will have been run through a machine that splits it into two or more thinner layers.
Top Grain and Tumbled Leather
The top layer of split leather is called top grain leather. Seeing as the top grain leather is made from the part with the tightest fibres it’s still very strong, a lot less bulky and easier to work with. Top Grain leather will usually be finely sanded or buffed to smooth it out, and then sealed with a finish – this could be a kind of synthetic coating or traditional waxes and oils. The finish will take away some of the breathability but also improve the overall durability of the leather. Tumbled leather is generally top grain leather that has been spun in a machine with a bunch of small stones. This process loosens the fibres, brings out the leather’s natural grain and gives it a soft, semi-sheen surface. Full grain leather that has been through the tumbling process is known as nappa leather.
Corrected Grain Leather
Corrected grain leather is usually made from the lower quality split leather which comes from the under side, and also known as the drop split. This has an artificial grain stamped on, to give it the appearance of top grain leather, or sometimes to make it look like another kind of leather entirely – like on the recent Nike Premium ‘Ostrich’ Pack, for example. The most common corrected grain leather you’ll see is pebble grain, also known as Scotch grain – as seen on the recent women’s Air Force 1 SE. The look is said to have been pioneered in Scotland, using leftover grain from the whisky making process to shrink hides and emphasise the natural grain, although these days it’s applied with a pressing machine. Whenever you see the ‘Genuine Leather’ label, it means you’ve got corrected grain leather, it’s a nice way of saying ‘it’s leather, but it’s not all it may seem.’
At the bottom of the leather ladder you have bonded leather – this is the leather equivalent of chipboard. It’s made from scraps that have been shredded and bonded together with glue, such as polyurethane or latex, and then laminated to a woven backing. This is the cheap stuff that often looks and feels a bit rubbery and will often have gaudy faux croc skin, or some other over the top grain embossed into it.
Suede and Roughout Leather
Suede is commonly believed to be the reverse side of leather, which is not strictly true. If you simply flip over a hide of leather you have what’s called roughout leather. Most suede is drop split leather, which has been sanded or buffed to tease out the fibres. The fuzzier the suede, the lower down in the hide it is likely to have come from – the recent mita x ASICS is likely to have come from the bottom, or flesh side, for example. Because suede it so porous and has no protective finish, it tends to scuff easily and soak in any moisture that it may come into contact with.
Nubuck, Patent, Pull Up and Shell Cordovan
Nubuck is similar to suede, except it’s created from the top grain split of the leather. The tightly packed, short fibres on the grain side are tease out by light sanding, to give them a soft finish that will occasionally maintain some slight patterning. Patent leather is traditionally made with lacquers or layers of wax polish, but you’re much more likely to see it as a plastic finish these days. Occasionally you’ll hear the term Chromexcel leather thrown around, a kind of waxy leather made my Horween, generically known as pull up leather. You can tell this from the way the colour gets lighter when you bend the leather, as well as a tendency to scuff easily. Shell cordovan is a kind of leather made from the butt of a horse, while things like calfskin and pigskin tend to be fairly self explanatory.
There are also plenty of exotic leathers, such as lizard skin, crocodile, elephant, turtle, hippo, fish… The list goes on. It’s highly unlikely that you’re buying a pair of ostrich skin Air Force 1 or snakeskin Stan Smiths that they will be the real deal, they’re more likely to be corrected grain leathers, with the patterns stamped on. The rarity of these exotic leathers means they tend to be hard to get and very expensive – plus, big brands like Nike and adidas have stopped using most of them due to pressure from animal welfare organisations like PETA. For the most part, these kind of leathers are the realm of customisers.
Although it all comes from the same place, each different kind of leather can have remarkably different qualities and give us all kinds of sneakers. It’s no coincidence that early models had names like PUMA Suede or Converse Pro Leather, it didn’t take long for people to realise just how durable and versatile it can be.