Have you ever noticed the outline of coins or cards showing on the surface of your leather wallet? When hard objects press against leather for an extended time, it can leave an imprint, known as a pressure mark.

Leathers tanned with tannins tend to be more susceptible to pressure marks, as the fibers adapt readily to pressure. It’s especially noticeable in soft, richly oiled leathers like our signature Soft Nume Leather used in our Tone Nume series, or Oil Mellow Leather used in our Diario series.

Pressure marks vary depending on usage, creating one-of-a-kind marks that reflect your lifestyle. In fine-grain leathers like cordovan, and leathers with a high oil content, the edges of the marks tend to appear softer, lending the piece a well-loved, lived-in feel.

Leather is made up of collagen fibers, which by nature, do not bond strongly with dyes. As a result, exposure to friction, moisture, or prolonged contact with other materials can cause the color to fade or transfer onto objects in contact. Conversely, the opposite can also occur: dyes from other materials can transfer onto leather—this, too, is referred to as color transfer.

Naturally finished leathers like nume leather (see Glossary Vol. 2) are especially prone, as they are seldom treated with fixatives in order to preserve the leather’s original texture and character. On the other hand, patent leather (leather treated with a glossy varnish) rarely fades, but can still pick up color from other materials that it comes into contact with.

Leather is typically composed of two main layers: the grain layer on the surface and the dermis layer beneath, which is made up of a dense network of fibers. In cowhide, the bond between these two layers tends to be relatively strong—but in other animals, it can be much looser. Even within a single hide, some areas—such as the belly or sides—may have weaker bonding.

When leather with a looser grain structure is repeatedly bent or exposed to moisture, the grain layer may begin to lift or separate from the dermis underneath. This is known as loose grain (gin-nuki in Japanese). Loose grain can appear as a puffed, swollen area, or as fine creases that are barely noticeable. It’s commonly seen in the flex lines that form across shoe tops.

Loose grain does not occur in cordovan (which does not have a grain layer) or in suede and velour, which are made using the underside of the hide.

In leather that has been heavily infused with oil, pressing from the back causes the oils and dyes to shift outward, lightening the color at the point of pressure. This phenomenon is known as the pull-up effect, and it also appears when the leather is bent, folded, or creased.

When this effect is deliberately enhanced through kneading or wrinkling techniques, the leather is referred to as pull-up leather. It responds to movement and pressure, creating a bold, richly variegated surface—where light and dark tones mix to express a wild, dynamic quality.

Bloom refers to the fine white powder that surfaces on leather infused with oils or wax. It’s especially prominent in bridle leather, a type of waxed leather that contains a generous amount of tallow—a special kind of wax. In some cases, the bloom can appear thick enough to coat the surface. A lighter version may also emerge on oil-rich leathers.

Bloom can be gently rubbed back into the leather with your fingers or with a soft cloth. If there is a significant amount, it can also be removed with a soft brush. That said, many bridle leather owners choose to leave the bloom intact, appreciating the stately, dignified presence it lends to the leather. Watching the bloom gradually fade with use is part of the unique aging experience that makes bridle leather so beloved.

Exposure to sunlight, heat, or artificial light can alter the color of leather—sometimes enhancing its richness, other times causing damage.

Darkening occurs when the tannins and oils in the leather oxidize under light or heat, resulting in a deeper, richer tone. The extent and speed of this change depend on factors such as light intensity, heat exposure, and the type and amount of tannins or oils used. In many cases, this is considered a natural part of leather’s aging process and contributes to its patina.

Conversely, some pigments and dyes used to color leather are prone to fading (taishoku) when exposed to sunlight or strong indoor lighting. Brightly colored items are especially vulnerable to fading if stored in direct light for extended periods. To preserve their vibrancy, store such pieces in shaded or dark areas whenever possible.