Glossary of Terms - Optima Leathers

optima leather's glossary of terms

Always remember that leather is a natural product. The variations in hides are a part of the beauty that only leather can produce. Because of dying techniques and certain qualities some hides will vary more than others. We are providing you with a brief glossary of some of the most important leather terms to help you evaluate leather qualities for your clients.

The term aniline dyed is often misunderstood and sometimes confusing. Full or pure aniline leathers have no pigment substances applied to the surface. Aniline leathers offer a soft, mellow hand and are considered to be the most luxurious of upholstery leathers. This process typically has little barrier substances to protect again spillage or staining. Full aniline dyed leathers should be selected with this in mind.

Optima’s process of pigmentation is unique and offers the look and feel of a full aniline dyed leather without the maintenance issues. It is also more consistent since there is a color applied to the hide.

THE PROCESS

Making leather is a complicated process. The easiest way to understand the process of leather preparation is to understand the layer separation in which the leather is split across it’s thickness to produce a top layer (hair side) and the under layer. The top layer is called the grain and is the side exposed to the elements giving it the durability and malleability it needs to be considered fine leather. The underside is much stiffer and less durable than the top layer. This is practical for use after a coating or treatment is applied.

The process of tanning involves five distinct stages. Tanning, Selecting, Splitting/Shaving, Re-tanning and Finishing. Each one of these processes is complicated and requires many steps. The following is an outline of some of the more important points of each step.

Step 1: Tanning

Soaking - When the leather arrives at the tannery it may be soaked to extrude salts used in preserving leather. This is done in revolving drums which can hold up to 200 hides.

Liming - Hair and epidermis are removed and a solution of lime (calcium hydroxide) and sodium sulphide are applied to soften and enhance hide for softness and flexibility needed for upholstery leather.

This is the process which converts pre-tanned hide into leather.

Mineral tanning is normally done with alkaline chrome-3 salts. It penetrates the hide fairly quickly (24-48 hours). This results in a pale duck-egg blue, which after processing yields a fine, soft, modern finish. When there is absence of chromium tanning, other methods combine vegetable with polymers and syntans as an alternative.

Other tanning methods are: (more information on these tanning methods are in the Glossary)

Pure Vegetable Tanning
Synthetic Tanning
Oil Tanning
Combination Tanning

Step 2: Selecting

After tanning excess water is removed from hide. Hides are then graded according to the quantity and locations of natural features and faults. Aniline and Nubuck leathers demand the best quality hides. Leather where hides that are heavily coated or embossed can utilize a lesser quality of hides.

Step 3: Splitting/Shaving

Splitting - The hide is split into layers. The top or grain layer will produce a fine, smooth grain leather. The bottom is used for suede or split leather for other uses.

Shaving - Given a uniform thickness.

Step 4: Re-Tanning

Dressing the hides involves the following:

Dyeing - Dyes are added to color leather.
Re-tanning - Additional tanning substances are sometimes added to modify the physical characteristics of he leather to suit its final use.
Setting - A process which mechanically removes creases and excess water.
Drying - The hides are stretched dried on large frames or vacuum dried.
Trimming- The rough and ragged edges are removed.

Step 5: Finishing

The purpose of finishing are:

To minimize the appearance grain blemishes without losing the natural beauty of the leather product.
To give the required degree of gloss.
To ensure the leather is soft, malleable and moldable.
To give a more protective surface.
To provide a surface which is easily cleaned.
To give special effect like antique or special grain effects.

The finishing process uses a combination of surface coatings techniques such as padding, spraying or roller coating. Then there are mechanical processes such as buffing, staking and embossing.

GLOSSARY

Aniline Dyed or Aniline Leather - Leather that Has been dyed in a dye bath with some level of dye penetration.

Blues, in the - The state of hides which have been tanned once using chromium salts. This results in hides that are light blue in color.

Bovine - An animal belonging to the cattle or ox family

Breathability - An important characteristic of full-grain leather. Due to its intact grain and pore structure. This means the leather adjusts to temperature and wicks away moisture and body heat, making it extremely comfortable.

Brush Coloring - The process of applying dyestuff to the leather by means of a brush. This is a cosmetic process. Dyes are not saturated into the hide.

Buffed Leather - Leather from which the top surface grain has been removed by abrasive or bladed cylinder; or less generally by hand. In the case of upholstery leather the buffing process is invariably carried out by machine though sometimes incorrectly described as “hand buffed”.

Chamois Leather - Leather made from sheep or lambskin from which grain has been removed in the tanning process using oils.

Chromium Salts - Minerals used in the tanning process to make the leather supple and durable.

Chrome Tanning - Leather tanned either solely with chromium salts or with chromium salts together with quite small amounts of other tanning agents used merely to assist the chrome tanning process, and not a sufficient amount to alter the essential chrome tanned character of the leather. Chrome tanning results in soft, mellow hides receptive to excellent color variety.

Combination Tanning - Leather which receives chrome and vegetable tannage producing suppleness and body in hides. Some tanning agents can penetrate notably but not necessarily into the interior of the material.

Corrected Grain - Commonly referred to as top grain. Lacking an intact full grain surface. Usually heavily pigmented or another surface appearance which has been built by various finishing techniques.

Curing - Tanning process of cleaning the leather - consists of soaking, liming and fleshing.

Drum Dyeing - The application of dyestuffs to leather by the immersion of the leather in a drum that is tumbled. This process allows full dye penetration into the fiber.

Embossed Leather - Usually corrected grain, in which a pattern is applied by extreme pressure in a press to give a unique design or imitation of full grain characteristics. Sometimes embossing emulates other leathers such as an alligator.

Fat Wrinkle - Wrinkles in the grain of leather caused by fat deposits in the animal that are part of the beauty in leathers. Fat wrinkles are not visible in imitation or inferior leathers.

Finish - Generally defines a surface application on leather to color, protect or mask imperfections. More specifically it refers to all processes done to leather after it has been tanned.

Full Grain - Leather bearing the original grain surface as exposed by removal of the hair and with none of the surface removed by buffering or splitting. This grain is what gives each type of leather its distinctive appearance and style.

Glazed Finish- a glossy, smooth, sheen imparted to leather by polishing with a glass or steel rollers.

Grain - The pattern characterized by the pores, cells, wrinkles and other characteristics which constitute the natural texture of leather.

Grain Character - The natural markings on the surface of the leather.

Embossed Grain - An artificial grain pressed into the surface of the top grain leather from which the original grain has been removed.

Grain Layer - The portion of a hide or skin extending from the surface exposed by removal of hair or wool.

Grain Sueded - A buffing process to raise the fibers on the grain side of a hide or skin to produce a velvet-like effect. This is also known as “Nubuck” leather

Leather - Hide or skin which retains its original fibrous more or less intact. The hide is then treated and colored to enable it to be a covering for furniture, walls or floors. The hair or wool may or may not be removed. In the case of the “hair on hide”, typically it is referred to as fur.

Liming - The process of removing the hair from a hide preparing hides for tanning process.

Metalized Leather - Leather given a metallic luster by application of metallic foils or powders.

Napa - Soft full grain gloving or clothing leather made from unsplit sheep or lambskin or kid-skin. It is usually tanned with alum and chromium salts and dyed throughout the substance.

Nubuck - Cattle hide leather buffed on the grain side to give a velvety surface; white or colored.

Parchment - Translucent or opaque material with a smooth surface suitable for writing, bookbinding and other purposes. It is made from the hides of sheep or goatskin by drying out the limed material without applying tannage. The material being thoroughly cleansed and degreased and smoothed during the process.

Patent Leather - Leather with a glossy, impermeable finish produced by successive coats of drying oils, varnish or synthetic resins.

Patina - A natural characteristic that develops on full grain leather through normal use over a period of time. Another term used interchangeably is “weathering”.

Pearlized - Colored leather which results in a pearlized or soft sheen luster.

Perforated - Small die-cut holes that form a pattern. The hole size and pattern may vary.

Pigmented Finish - Leather whose surface has been finished with an opaque finish.

Plated Leather, Plating - Pressing leather with a heated metal plate under high pressure to cover imperfections.

Printed Leather - Leather which is either embossed or silk-screened.

Pull-Up - Full grain leather that derives its color from dyes. When leather is pulled, the oils or the waxes in the leather cause the color to dissipate and become lighter in areas which are pulled tight.

Sauvage - The two tone effect with a mottled appearance that adds depth and character to the leather. Created two ways; by blending similar colors during the dyeing process or by mechanical process during finishing.

Selecting - The sorting or grading of hides and skins using predetermined criteria such as area, thickness, grain quality.

Semi-Aniline Leather - The term is used to describe aniline dyed leather which has only a small amount of clear or pigmented finish. Leather whose surface coating only partly obscures the natural grain.

Shave - Hides are shaved to a particular thickness after tannage by a large shaving machine. The excess is removed from the bottom of the hide.

Shrunken Grain - Leather specially tanned so as to shrink the grain layer and having a grain surface of uneven folds and valleys. Sometimes referred to as “drawn grain”. This process is used to enhance the grain character of the leather.

Split leather - Leather made from the bottom split. By and large these splits are embossed to emulate hide grains.

Strap Leather - Heavyweight, vegetable tanned leather usually used for industrial use.

Suede - Velvet-like nap finish produced on leather by abrasive action. This is generally called Nubuck or grain sueded.

Tannin - Any various solvent, astringent substances of plant origin used in tanning leather.

Tanning - Processing whereby raw hide and skins are converted into leather.

Tipped Leather - Leather which has a contrast color coat (either lighter or darker than the base shade) applied by a roller to the tips of an embossed grain.

Top Grain - An overused term commonly used to refer to corrected grain leather.

Trim - The removal of the outer edges of the hide not suitable for making leather.

Top Finish - leather which has been given a final coating of a finish to confer special properties such as gloss, color level, fastness to wet and staining.

Vegetable Tanned - Leather tanned exclusively with vegetable tanning agents, or with such materials together with small amounts of other agents used merely to assist in the tanning process. Vegetable tanning is principally used to produce firm, non stretchy leather for shoe soles, belts and other leather goods.

Wet Blue Leather - Leather which after chrome tanning has not been further processed and is sold in wet condition.

Yield - The amount of useable area after all waste and imperfections have been discarded.