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Leather Tanning Methods

Leather Tanning Methods

Posted by Daniel Sutton on Apr 20th 2014

Hello, everybody! Today we’re going to dive into a feud of titanic proportion. It’s a controversy that has erupted over a tradition sacred since the days of ancient Egypt, Greece, and the Roman Empire. I won’t sugarcoat things – this is a sensitive topic, and for that matter, a sensational one. Get ready for a riveting showdown that will test the limits of your leather down to the very fibers of its being. In this case, I’m talking quite literally. Topic of the day: chrome leather tanning vs. vegetable leather tanning.

For those of us that are not leather experts and know-it-alls, allow me to set the stage. Tanning is a step in the process of making your leather. It occurs after the preparatory phases, which include soaking the leather, cutting out all the fats, hairs and oils, temporarily preserving the hide from decay, washing, bleaching, pickling to lower pH levels, and additional modifications to ensure you are not going to end up with a glob of icky stuff by the end of the process. This stage also determines how the leather is to be cut, whether full grain, top grain, genuine or otherwise. You can read about the advantages and disadvantages of these cuts in our blog “Know Your Leather Grains.”

After the preparatory phases are complete, your leather’s going to end up very stiff and inflexible, not like the supple stuff you’re used to feeling. It’s very fragile as well, capable of decaying again when rewetted, and otherwise very far from what we want leather to look like. Thus we begin the leather tanning stage.
The point of leather tanning is to make stiff, raw cowhide (or whatever other animal you are working with) into a durable, flexible material receptive to conditioners and cleaners like Chamberlain’s Leather Care Liniment No. 1 without going off and decaying. To this end, it is soaked in a solution that converts the skin’s proteins into a more resilient form. This is where chrome leather tanning and vegetable leather tanning come in, and our fun game begins.

Tanning Your Hide

Vegetable tanning has a few years on chrome tanning. Like, a few thousand years. Whereas chrome tanning started coming into use by the 1850s, vegetable tanning, or varieties of it, have been in use since Ancient Egypt and Greece. Since that time, it has been developed and improved considerably, but is now represented by under ten percent of all US's tanned leather produce. Part of the reason is because of the length of time it takes to make this leather. Whereas chrome tanning can take less than a day to produce leather, vegetable tanning can take upwards of forty to sixty days. Additionally, the task requires experienced craftsmen to maintain them using methods mostly by hand. The materials used to create vegetable tanned leather are entirely natural, and as it is created individually, each piece will be unique. Indeed, this leather actually improves with age, and is most likely to develop a patina. Unfortunately, because it is entirely natural, it also needs more maintenance than other leather types. Vegetable tanned leather stains very easily, is more susceptible to heat, and very susceptible to water. Because of this, vegetable tanned leather may require more regular cleaning to remain healthy (read about cleaning and conditioning routines in our blog "How Often Should I Condition Leather?". Due to the immense amount of time it takes to produce one of a vegetable tanned hide, they also veer on the more expensive side, and are a bit more difficult to find.

Chrome tanned leather, on the other hand, is highly available, accounting for ninety percent of U.S. produced leather. Chrome tanning differs from vegetable tanning in that it soaks the stiff cowhide in a solution of chemicals, acids and salts to dye it, usually by three different methods: aniline, semi-aniline, and pigmented. You can read about that in our blog "How to Identify Types of Leather." As I mentioned earlier, this process is very quick, usually finished within a day. After allowing the leather to be pickled in an acid salt mixture, it is moved into chromium sulphate bath, raising the pH and restoring the leather to a more flexible state. The hides come out of this looking a light blue color, which is where a dye is usually applied. The chemicals used in this formula give the finished product a very supple texture with a resilient color that will be hard pressed to fade. The material is also highly thermal and stain resistant, with water often just rolling off its surface rather than setting in, and can absorb more varied temperatures without harmful effect. Due to its abundance, it is also generally much more inexpensive. Unfortunately, the chemicals used tend to be less beneficial to the environment, and does not wear very well, drying out at a quicker rate, which means it may need to be conditioned more than vegetable tanned leather. It also appears and smells less natural than vegetable tanned leather, and appropriately so; it is, in fact, less natural.

Apart from actually asking a retailer what type of leather item you are looking at, there are a few ways to tell the difference between vegetable and chrome tanned leather. First would be the smell. If the leather smells more chemical based, it’s most likely chrome. Of course, this is not always the case. Scents can be achieved in the leather production process through many different methods, with many chrome tanned leathers smelling quite natural. Your nose may mislead you. Another more reliable method is to scratch the leather product. I would not recommend doing this in stores, as a scratch that is difficult to rub out will likely indicate you are looking at chrome leather, and you just kind of messed with someone’s merchandise. Naughty, naughty! Vegetable tanned leather tends to more easily buff out scratches, however, so you’ll be a little more safe with these. Thirdly, you could try my favorite technique. Burn the bag. Burn it with fire. Simply hold your handy lighter up against your leather and watch what happens. I’m not kidding. If it is vegetable tanned, it will have almost no effect on the leather, and any ash it does produce will be a grey color. Chrome will be a bit more receptive to your flame (it will burn), and will yield green ash. As a bit of a common sense warning, don’t do this to anything valuable, and seriously don’t do it at the store. This last test should really only be used if you know the quality of the leather you are holding, and chances are, at that point, you already know what kind of tan you’re dealing with. This is just for fun, and science.

Decisions, Decisions

In the end, which kind of leather you should end up getting will likely hinge on what you are looking for. Chrome tanned leather is a great product highly resistant to the elements and relatively easy to maintain, and available for a much more affordable price. If you are looking for a more natural variety of leather with greater longevity, a distinctive, elegant appearance, and money is no factor, vegetable tanned leather is probably for you. Both leather tanning methods have excellent merits and have produced incredible quality leather. In fact, look no further than Saddleback Leather for the pinnacle of what chrome tans can do for you - this stuff is real. So who’s going to be your next best friend? Better get on that, chief. Cowhide awaits.

Daniel Sutton

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