Horween Chromexcel—or CXL, as they call it in the Chicago tannery—has certainly established itself as one of the deservingly premier leathers for high-quality boots and shoes. The pull-up leather is soft and pliable but highly durable, easy to work with throughout the shoe- or boot-making process, and at its best, looks absolutely stunning when worn hard.

Natural Chromexcel is a dye-free version of Horween’s flagship leather…and offers sure-thing aging potential that few other leathers can.

So what is this stuff? What goes into making it? And how can you expect your pair of natural Chromexcel leather boots or shoes to wear and patina over time? Well, that’s what we’re here for…

What is Chromexcel Leather?

Chromexcel is a legendary Horween leather that has stood the test of time, made for over a century with a formula that has been largely unchanged since the first sides of CXL came out of Horween’s doors.

Interestingly, when Chromexcel first appeared in 1913, it wasn’t meant for shoes or other personal leather goods; instead, its main application was for mechanical purposes, like in motor seals and gaskets in trucks and even tanks (the first World War broke out not long after the leather was first released).

Today, it is one of the most ubiquitous and popular shoe leathers out there, and for good reason. CXL is a combination-tanned leather—it’s chrome-tanned, followed by a vegetable (tree bark) re-tan. Chrome tanning provides the leather with a soft suppleness, while veg tanning gives the leather a more rigid temper and a better chance at developing patina.

With a combo-tanned leather like CXL, you’re basically getting the best of both worlds. CXL is quite pliable but has a strong “backbone,” and it can take a shine or be left alone to age ruggedly.

horween tannery chromexcel

Additionally, CXL is hot-stuffed with a proprietary blend of oils, waxes, and grease. This provides the leather with its signature pull-up effect, where the oils and waxes disperse and lighten up when the leather gets pressed or pulled. Hot-stuffing also provides the leather with additional softness and water resistance. After hot-stuffing, most CXL will be hand-coated with aniline dyes and then finished with neatsfoot oil. (For a great look at how CXL gets made from beginning to end, check out Nick Horween’s blog.) 

horween chromexcel oil

In the case of Natural CXL, those dyes don’t get applied. What we’re left with is a sort of beige tan color, the tone and intensity of which can vary from hide to hide. That natural canvas provides a great starting point for all kinds of wonderful patina to happen.

How Natural Chromexcel Ages on Viberg Service Boots

For an excellent example of how this leather ages, let’s start by looking at the Natural CXL pair from the champion of our inaugural Patina Thunderdome, Steven Lee. Steven participated in a pair of Viberg x Lost & Found Service Boots in Natural CXL.

Month Zero

In the beginning, the leather on Steven’s boots looked fairly uniform. A couple of subtle dark spots here and there where the oils and waxes were concentrated, but nothing crazy.

steven lee patina thunderdome horween chromexcel viberg service boot

steven lee patina thunderdome horween chromexcel viberg service boot

Months Three and Four

Here we can see the leather really began to come to life. Creases became pronounced as the leather broke in and began to mold to Steven’s feet—luckily with some fairly tight break. (Chromexcel is infamous for having some wild crease lines.) Scuffs and other spots of heavy wear became darkened and set in. The overall color became more of a light brown.

steven lee patina thunderdome horween chromexcel viberg service boot

steven lee patina thunderdome horween chromexcel viberg service boot

Month Seven

When we finally arrive at the end of the contest, we can see that this CXL has achieved a surprising degree of depth and beauty. The color could best be described as “burnt sugar.” Not only has the leather taken on a bold patina, Steven has also been able to get it cleaned up quite nicely, providing it with a terrific shine.

steven lee patina thunderdome horween chromexcel viberg service boot

steven lee patina thunderdome horween chromexcel viberg service boot

How Natural Chromexcel Ages on Oak Street Bootmaker Trench Boots

Let’s take a look at another Thunderdome pair. These Oak Street Bootmaker Trench Boots were worn by Phil Kalas, co-founder of Ashland Leather (who also happens to be a former Horween employee). They’re not too different from where Steven’s pair started.

Month Zero

phil kalas patina thunderdome natural chromexcel oak street bootmakers trench boot

phil kalas patina thunderdome natural chromexcel oak street bootmakers trench boot

Month Four

At the time Phil took these check-in photos, he’d just been walking through some slush and snow. CXL takes on a much darker and more matte appearance when it gets soaked, and while the contrast may seem alarming, the leather’s lighter color and luster will return after drying and getting a good brush.

phil kalas patina thunderdome natural chromexcel oak street bootmakers trench boot

phil kalas patina thunderdome natural chromexcel oak street bootmakers trench boot

Month Seven

By the end, Phil’s boots look incredible. The toe caps alone have a whole universe of patina in them. It looks like Phil wore these hard, but lovingly.

phil kalas patina thunderdome natural chromexcel oak street bootmakers trench boot

phil kalas patina thunderdome natural chromexcel oak street bootmakers trench boot

How Natural Chromexcel Ages on Easymocs

Our third example is a Thunderdome pair that was worn by Chris, who goes by the handle MonsieurLeDude over on Reddit, where he compiled this excellent and thorough retrospective of his experience wearing the eponymous Easymoc.

Month Zero

patina thunderdome natural chromexcel easymoc patina thunderdome natural chromexcel easymoc

Month Two

Already, the aging here is quite advanced, especially around the collar (an area of high wear for shoes that are easy to slip into like the Easymoc). Chris said he wore these shoes more often than any other pair before, and it shows.

patina thunderdome natural chromexcel easymoc

Month Seven

Finally, at the conclusion of the Thunderdome, you can really see that these Easymocs were pushed to the limit. While the insoles look pretty rough and these are likely ready for a resole, the CXL uppers have broken in magnificently.

patina thunderdome natural chromexcel easymoc

patina thunderdome natural chromexcel easymoc

In Conclusion…

Whether you’re looking for a pair of boots that’ll clean up nicely, take a beating, and/or for a project like the Patina Thunderdome…you could do a lot worse than Natural Chromexcel.