Creating Leather Watch Bands
Last week we started to look at leather, with the aim of understanding how to identify great leather watch bands. The first step is to de-nature the animal skin so that it does not rot. After the tanning process, the resulting leather is not something we would recognize or particularly want to use. The leather that emerges from the tanning process is a slimy mess, and if it is dried, it turns into a very tough and lifeless material. It is not attractive or pleasant to wear leather in this state, and it would certainly not be a good accessory to your watch.
We pick up the story when the skins have just finished the tanning process. At this stage, the skins are either “wet blue” if chrome tanned or “crust” if vegetable tanned. The next crucial step is to ensure all the skins are of consistent thickness. When processing the skins through the post tanning steps, all the skins must be the same thickness; this ensures all the skins from a single bath have the same properties. The skins are shaved to ensure they are all the same thickness, they are also trimmed too so the skins are approximately the same size.
How Would You Like Your Watch Band To Feel?
Next is to make the leather hard or soft depending on its specific use. For example, a dress watch may need a leather watch band made from very soft supple leather. By contrast, harder and more robust leather is necessary for leather that will be used for an alligator embossed leather watch band. The final feel and physical properties of the leather can be adjusted in the post tanning process.
Whereas the tanning process focuses on removing the leather’s natural characteristics, the next step is all about making the denatured leather feel natural. All the natural oils are removed from the skin by the tanning process. Replacing them is essential to ensure a good feel to the final leather.
Some Nature Has To Return To The Leather
Fatliquoring is the process that introduces oils back into the skin so that each leather fiber has a coating of oil. Oil is introduced into the leather by placing all the skins into a large barrel, the fatliquor is placed in the barrel and they are tumbled together until the desired physical properties are achieved. The oil penetrates the leather, coating the fibers of the leather. Depending on the oil used and how much is allowed to penetrate the leather determines whether the resulting leather is soft or stiffer. This is not a scientific process, the tanner needs to supervise this step carefully because depending on the thickness of the leather and exactly how it was tanned, the time required in fatliquoring can change.
From a user perspective, you can understand the impact of the fatliquoring process as follows. When a piece of leather gets wet, it becomes quite slippery and slimy, but when it dries out it becomes very stiff. The reason for this is that some of the oil has been removed with the leather becoming wet. It is for this reason that leather generally needs to be protected from becoming soaked and should be treated periodically with a leather wax or cream to ensure that the leather maintains some oil between the leather fibers.
From Touch, To The Visible Appearance
Once the leather has the desired physical properties, the next step is to ensure the leather has the correct visual properties. Things become very complex, mainly because there are so many ways to alter the appearance of leather. I will cover the most common methods that are applicable to watch bands, but this is not an exhaustive list of leather processes by a long way.
Adjusting the Leather
Color is the most prominent treatment to the leather, but there are many other surface treatments that will give the leather the desired texture, or some other functionality such as water resistance. One of the most common treatments is the use of fillers. Leather is a natural material so has flaws in it; this comes from scars the animal has collected along its lifetime. These can come from ticks, cuts, or other imperfections in the animal’s skin, and unfortunately, the tanning process accentuates these imperfections. These imperfections can be covered with what are called fillers. These can be combined with a variety of surface treatments to create a specific color. More on that later.
Adding Color For The Watch Band
The color of the leather can be altered in a variety of ways. The colors available though do depend on the tanning method. To start with, the colors available to choose from differ depending on whether the leather is vegetable tanned or mineral tanned. Colors for vegetable tanned leathers tend to be less bright and more variable across the surface of the leather. Mineral tanned leather can take any color you choose. These variations are due to the way that the chemicals that add color interact with the leather.
A Little Bit Of Chemistry
In chromium tanned leather the chromium reacts with the collagen in the skin to create very long molecules or fibers. These fibers have chromium ions interspersed along their length. Chromium ions in the fiber create excellent bonding locations for the colorants to stick to. With a known mechanism for the colorant to adhere to the leather structure, the chemists can make any color penetrate and bind in the leather. The other benefit is that the color is strongly held within the leather fibers, so it will not come out of the leather and stain material that comes in contact with it.
Vegetable-tanned leathers are quite different. Tanning using vegetable tanning is a different chemical process. For those that can remember their chemistry from school, mineral tanning is the equivalent of ionic bonding the collagen of the skin together. Vegetable tanning is analogous to hydrogen or covalent bonding the collagen structures together into fibers.
The covalent structure of the vegetable-tanned leather means that the color does not bind to specific sites in the fiber structure. The colorants are therefore less firmly held within the leather fibers so the colorant can leach out of the leather if it gets wet or through repeated physical contact. If you have an old-fashioned pair of boots that require regular polishing, these are probably made from vegetable-tanned leather, and you will notice that when they are new (or your feet get wet), the color leaches into your socks.
How Is It Done?
There are two principal ways to color leather. The first is to put the leather into a giant vat of dye and tumble the leather in the dye until the dye has penetrated the full thickness of the leather. This dying process results in a leather that is referred to as full thickness dyed.
There are more ways to change the color of the leather, but these tend to only change the color of the surface of the leather. A dye can be painted or sprayed on top of the leather. In many situations, an acrylic spray is used to color the top of the leather as this will also act as a filler and ensure a flawless finish. The topcoat though is effectively a very thin plastic coating, that is why when you touch some leathers, it feels plastic-like to the touch, and on some cheap leather, you can detect it with the smell of plastic!
Drying The Leather
Once the coloring is complete the tanned and colored skins are stretched out and dried. It is essential that the tannery dries the leather correctly because the leather is damp it will grow mold quickly.
Once dried, vegetable-tanned leather is generally ready for use. It can go for further processing, such as dry tumbling, which softens the leather further or can create an accelerated patina on the leather. There is one final step that is very common for many types of leather, this is called plating.
Plating The Leather
This final step in finishing the leather brings flair to the finished skins. Plating can affect the color but it is focussed predominantly on the physical texture, or pattern, of the final leather. The truth is that when you see a crocodile patterned watch band, the pattern was most likely created by plating the leather. The pattern is created by embossing the desired pattern into the leather through the plating process.
Plating gets its name from the plate that is used to emboss the pattern into the leather. The plate is a large steel sheet that has a negative pattern that will be embossed into the leather etched into the steel. The plate is placed on a large press and heated, then pressed between the plates under pressure and the pattern from the plate is embossed onto the leather.
There Is So Much Variety
There is no end to the variety of patterns that plating can emboss on leather. For most of us we are familiar with a crocodile belly pattern on many classic watch bands. But there are many other patterns such as snakeskin, ostrich skin, or Saffiano leather that can be applied onto the leather. Creating these patterns on cheaper cowhide leather means the beauty of these exotic skins can be appreciated at a much lower cost.
The other aspect is that special coatings can be applied through the plating process. These can be metallic finishes, special coatings, and even add colors to create two-tone leathers.
That Is How The Leather Is Made, How Do You Make A Watch Band?
I have summarised the principal steps that leather goes through from a raw tanned hide to a useable leather skin for, in our case, making leather watch bands. For us as watch enthusiasts, the key is how to use this knowledge to select the best watch bands for our watches.
Next time the knowledge we have accumulated here will be put to the test. First to explain how we design our watch bands and then to understand what to look for when purchasing a quality watch band.
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