The use of leathers is strictly related to the history of the origins of civilisation. From the cave paintings that date back to the Palaeolithic Era (approx. 20,000 years BC), we learn about the common, at the time, use of leathers as a raw material for the manufacture of outer clothing or bed covers. Scholars also point out that for the first time the term leather was used in the third part of the Book of Genesis. The ancient Arabs, commonly using leathers, developed a written procedure of tanning them. The instructions stated that: first skin, cleaned from fat and impurities, should be stored in flour and salt for three days. Then, the root of the plant Chulga should be grated using large stones and dissolved in water, then cover the inner surface of the skin with preparation obtained and leave for one day, after which the skin will lose its hair. The skin should be left in this state for another two days, after which the treatment process is completed. Thanks to this procedure, ancient Arabs achieved an excellent material for the manufacture of famous saddles.
Leather as an upholstery material is a special product due to its uniqueness and unique features of use. When choosing leather for the upholstered layer of the furniture piece, we usually accept traces of scars, scratches and stabs on its surface which came about due to natural causes, as well as differences in the texture and colour shades showing the uniqueness of nature. Undoubtedly, these features strengthen the belief in the authenticity of the natural origin of this product. Therefore, a set of lounge furniture made of hides of leathers of identical or similar colours, but with a unique surface texture, can be attractive.
In dermatological terms, the skin is an organ which covers and guards the organism. It consists of three layers: epidermis, dermis and subcutaneous tissue. The epidermis consists mainly of ageing epithelial cells, called keratinocytes, and creates several layers: basal, spinous, granular and cornified. In addition to kerat- inocytes in the epidermis, there are also colour cells—melanocytes, the cells responsible for immunological reactions—Langerhans cells and the cells of the nervous system—Merkel cells. In dermis, made of connective tissue, there are collagen fibres, elastin and cellular elements: fibroblasts, mastocytes, blood cells, vessels and nerves. The hypodermic tissue is created by the adipose and connective tissue. The skin has skin appendages: sweat glands (eccrine and apocrine), sebaceous glands, nails and hair. The skin protects against bacteria, fungi, virus infections, against mechanical, thermal, chemical and light radiation factors, as well as ensures constant conditions for the internal environment of the organism (ho – moeostasis). In addition to this, skin fulfils the following functions: perceptive (heat, pain, touch), expressive (in articulating emotional states), resorption and participates in storage and metabolism (Placek 1996).
As an organic material, such as wood, skin reacts to changes of external climatic factors, including light intensity, temperature and humidity of the environment. During treatment in tanneries, skin is subjected to complex processes, using moisturising substances, giving it softness and elasticity, however, during use these substances vaporise. Drying of the skin increases its fragility and susceptibility to cracking and flaking. In order to ensure its original elasticity and extend its lifespan, appropriate care and conservation agents should be used. Leather needs to be conserved and cleaned every 3-6 months, depending on its kind and degree of exploitation of the product.
From the commercial point of view, the following kinds of leathers are distinguished:
• madras is the basic kind of single-colour leathers with an adjusted grain. Adjustment of the leather consists in polishing the grain and embossing appropriately regular cracks on its surface;
• modial, grain leather, two colour, with identical properties to madras;
• antic, grain leather, adjusted and embossed, usually two colour and shiny with a grain size that is smaller than madras;
• lissone, split leather made in the production process through cutting (splitting) grain leathers. A smaller thickness of split leathers causes them to be more prone to stretching and mechanical damage. Usually, it is used as a coordinate material, a supplement of grain leather on a furniture piece; and
• reno, the best kind of leather with a partially adjusted grain, preserving the natural drawing and texture of the surface.
The fabric is a textile product woven on a loom (Chyrosz and Zembowicz – Sufkowska 1995). As a work of human hands, fabrics are much younger than leathers. They were made in the Neolithic about 8000 years BC. Initially, they were loosely laced grass fibres, thin creepers and leather straps. A true fabric of use and design value, similar to modern fabrics, was woven in ancient Egypt during the period of the Old Kingdom (27th-22nd century BC). It was a linen cloth commonly used by the Egyptians in the manufacture of clothing and upholstering furniture.
The fabrics are made of two systems of threads, warps and wefts. Combining these two systems according to a specific order (weave) creates the structure of the fabric. The quality of the material depends on the main structural parameters of fabric, which consist of:
• the weave, determining the appearance and purpose of the fabric. Freedom in linking weaves enables to obtain any number of fabric designs according to their purpose;
• the quantity (density) of the warp and weft, which affects the elasticity and permeability of fabrics;
• the weaving of the warp and weft is a percentage ratio of the difference in length of the thread between its length after straightening l and the length in the fabric lo to the length of the thread in the fabric W =100 %(l – lo)/lo. The size of the weaving has a significant impact on the elasticity and permeability of the fabric; and
• the thickness is the number of the yarn and its type. Thickness has a significant impact on the purpose of the fabric.
Taking into consideration the structure of fabrics, they can be divided into:
• single layer, characterised by the same appearance on both sides and
• multilayer, in which the appearance on one side may significantly differ from the appearance on the other side.
Due to the texture of the surface, we differentiate between fabrics that are as
• smooth, distinguished by an even surface on both sides and a clearly visible structure (plait);
• with hair (fleece) cover, characterised by a fluffy cover, hiding the fabric structure on one of the sides;
• with looped (terry) cover, characterised by total or partial looped surface on one or both sides of the fabric; and
• with mixed cover, distinguished by a partial filling with looped cover and fleece.
Depending on the raw material, among others, the following fabrics are distinguished: cotton, linen, wool, silk and synthetic fibres.