Dyeing & Finishing
Tanned leather is first colored with a penetrating dye. The dye permeates the surface of the hide giving it color, but not covering over natural markings. The leather can then be finished in one or more coating operations, with clear or pigmented finishes that do not penetrate the surface. These final finishes provide abrasion and stain resistance as well as color enhancement. Generally, the more surface finish leather has, the stiffer it becomes, but tanning formula and hide quality also affect leather stiffness.
Aniline dye in common industry usage refers to any clear dye that penetrates into the leather, coloring it, but not coating its surface with pigment. Virtually all upholstery leathers are initially treated with a penetrating aniline dye, which allows the natural grain to show through.
The amount of dye used in leather production depends on the extent to which the dye has penetrated the leather. The dyeing of leather can be controlled by the manufacturer to either fully or partially penetrate it. Leather that has been fully penetrated with dye is known as fully struck through leather. If it has only been superficially dyed (only the flesh and grain surfaces penetrated), it is called partially struck through. For obvious reasons, leather whose cut edges will be exposed in the finished upholstered piece must have the dye fully struck through, but normal wear will not expose the interior of partially struck through leather.
The three most commonly available basic types of leather are pure aniline, semi-aniline, and protected aniline leather.
Pure aniline leather, sometimes called aniline leather, aniline finish leather, or premium select leather, is a product that has a clear protective coating but no applied pigmented surface coating (finish). This is the best quality and most expensive leather. It is made from hides having a minimum of natural markings which have not needed to be grain corrected, embossed, or coated with pigment. This leather may receive a clear protective coating, but not a pigmented coating. Natural characteristics of the hide show through and the surface is soft and supple. Moderate color variations are normal and these unpigmented leathers tend to develop a rich patina with age. Only a small percentage of hides are good enough to be converted into pure aniline leather.
Semi-aniline leather (aniline plus leather) has not as some believe had less aniline dye used in its manufacture than leather described simply, as aniline leather, pure aniline leather, or aniline finished. The term semi-aniline leather describes full grain leather which contains only a small amount of surface coating (finish), a premium product which allows most of the natural character of the leather to show through. It is, therefore, misleading to describe heavily finished or protected leather as being semi-aniline dyed.
Protected aniline leather is less expensive and more common than pure aniline or semi-aniline leather. Its coloration is more consistent and because it has been coated with protective pigments, the leatherĂƒ`s natural markings are less noticeable. Protected leather is more heavily pigmented than semi-aniline leather and is actually easier to clean than pure aniline leather because surface pigments repel water and stains.
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