Color and Design. Tutorial

samples in a color catalog, the use of which facilitates work in industrial conditions.

The correct choice of dye triads and careful adherence to the process parameters are essential. The use of dye levelers are required due to the different degrees of affinity of the individual dyes of the triad for the material to be dyed, as well as the difference in the structure and properties of the outer and down hairs. They are used to control the dyeing process.

In accordance with the color theory, the yellow dye should have the least complex chromophore system and, accordingly, a lower molecular weight than red dye and, especially, blue dye. It dissolves well in water and rather easily dissociates into ions. It is fixed on the fiber mainly by ionic bonds. Under experimental conditions, i.e. at pH = 4.5, corresponding to the optimal value at the initial stage of dyeing, the yellow dye interacts weakly with the hair. This is due to the absence of a positive charge on the amino groups of the protein. The interaction with the fiber due to the adsorption forces of this dye is low, since it has the lowest molecular weight compared to red and blue dyes. Blue dye is characterized by maximum affinity for the hairline. This is also in good agreement with the theory of color, based on which its chromophore system is the most complex. Therefore, its molecular weight is the largest. This dye is much more prone to interaction due to adsorption forces, which explains the high rate of its absorption from solution. Thus, the different affinity of the triad dyes for the material to be dyed is inherent in the nature of the dyes themselves, but it can be controlled by the introduction of equalizers.

Different levelers affect the affinity of dyes to fiber in different ways. Therefore, when moving from one leveler to another or when changing the concentration of excipients in a solution, a change in color tone and color saturation is possible.

Another important factor for controlling the dyeing process using triads is temperature. Depending on the temperature, the absorption of

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dyes by the fiber changes significantly. For different dyes of the triad, this difference can be expressed to different degrees. Therefore, a temperature change of even a few degrees can lead to a change in both the intensity of the color and the color tone.

There are advantages and disadvantages of fur dyeing using triads. The main problem of triad dyeing, compared with the use of individual dyes (for example, green, olive, etc.), is the need to control carefully all technological parameters: temperature, pH, concentration of dyes and

Imitation coloring of fur semi-finished products

It is known that the range of fur and sheepskin coat semi-finished products is much wider than the range of raw materials. This is explained by the fact that there are different finishing technology combining complex physical and chemical processes (dyeing, refining) and mechanical operations (cutting, pinching, ironing, embossing, etc.), which allow us to produce various fur and leather imitations.

According to the industrial terminology, “imitation” is a dressed skin which is dyed or sheared and refined to imitate valuable fur skins.

Modern combinations of well-known technological processes and operations are used not only to produce imitations of different furs, but also to eliminate defects on valuable furs, including astrakhan. They are used to create fantasy imitations for fashionable products.

Modern finishing methods allow us to obtain a high-quality semifinished product from low-ranking skins, expand the assortment of raw materials, and use more rationally traditional types of raw materials, including traditional types of fur and sheepskin coat raw materials.

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Nowadays, the imitation dyeing is widely used. New methods of finishing leather fabrics and the introduction of two-sided finishing in the fur industry diversify the range of products. In addition, the furrier and sewing industry also contribute to the expansion of the fur product range. Some types of cuts after stitching are subjected to additional finishing: shearing, picking, combing, etc. Sophisticated methods of cutting a semifinished fur product have been developed to create imitations of expensive types of fur skins. For example, the transfer method allows you to align properties with topographical areas and eliminate the visible features of individual topographical areas. With the transfer method, each skin from the side of the leather tissue is divided into an even number of strips, numbered, cut, and then all even-numbered and odd-numbered strips are sewn into separate plates. Thus, two parts leveled according to the properties of the hairline are obtained from one skin. This method is widely used to create chinchilla imitations from the skins of a chinchilla rabbit. Sewing strips of skins with different directions of the hairline

(stripes “against the wool” with stripes “along the wool”), with different depths of haircuts, and a combination of a curl group with a smooth-haired fur product provides unusual effects in fur products.

The combination of various finishing methods for creating imitations is very laborious. These operations lengthen the technological cycle, because they require repeated careful sorting and selection of semi - finished products. However, the ultimate goal (the transformation of lowvalue skins into noble imitations; the improvement of the quality of expensive raw materials) is cost-effective for the fur industry.

Combination of painting with dipping dyeing

Mass types of fur (sheepskin, webbing, rabbit skins, and muskrats) are usually the objects of imitations.

The color of imitated furs, as a rule, is two-tone. Therefore, to obtain this effect, a combination of several dyeing methods is required.

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To obtain imitations of valuable furs (otters, minks, martens, polecats, beavers, etc.) on a fur sheepskin or webbing, dipping dyeing is used in combination with spread dyeing (painting).

Stencils

Imitating mass types of fur for a wild cat, ocelot, smoky leopard, penguin, and cheetah may include a combination of dipping dyeing with a riding tip, which is carried out according to a special stencil pattern. Using various stencils, you can create two or three-color imitations (depending on the natural color of the simulated hairline) or fantasy ones.

Thus, stencil dyeing is a type of spread dyeing.

Punching

A rarer type of spread dyeing is punching, in which the dye solution is applied with stiff brushes over the entire area and depth of the hairline. This method is used to protect the leather fabric from the dye solution. It is used to process the skins of sea animals such as otters. The punching method is convenient for darkening the fur hairline.

Resist dyeing

Resist dyeing is used to obtain various effects on rabbit, sheepskin or red fox skins and improve the natural color of silver-black foxes.

During resist dyeing, the ends of the hair are left unpainted. They are protected against dipping dyeing applying a special solution, or reserve (resist). Then, the reserve is removed by washing. The unpainted ends of the hair have a silvery effect. This dyeing method will be discussed in more detail below.

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There are various types of imitations.

A white, long-haired, chinchilla and gray hare rabbit are dyed to imitate a dark sable. Some varieties of rabbit have an ugly shade of hair. Recently, they are often dyed with brown aniline paint “Urzol” to imitate the fur of sable.

A sheared rabbit is dyed like a fur seal. It looks like a cat. A rabbit is dyed to imitate dark brown nutria.

A rabbit is dyed to imitate the fur of marmot. A muskrat is dyed to imitate the fur of seal.

A groundhog is dyed to imitate the fur of sable.

A stone marten is dyed to imitate the skin of pine martens. Rabbit, opossum and muskrat are dyed to imitate the fur of mole. Fur sheepskins are dyed to imitate the fur of dark nutria.

The technologies of fur and leather dyeing are constantly being developed and improved. A number of successful inventions are being designed in this field.

Color effects

Fur dyeing in combination with bleaching is one the technologies for expanding the range of semi-finished fur products. The technology uses

the different color of the base and ends of the hair.

In this way, the “Snow Top” effect, as well as the effects of twoand three-color dyeing (“Briza” effect) can be obtained.

To obtain the “Snow Top” effect, the skins are dyed with appropriate dyes (Lowacene, Low-enstin) in the presence of levelers. After drying and ironing (for sheepskin), a bleaching composition is applied to the hairline with brushes or spraying, the main component of which are restorative bleaches. After application, the semi-finished product is subjected to thermal action or steam treatment. In an acidic environment

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at elevated temperatures, the dye is destroyed and the ends of the hair become discolored.

The “Briza” effect is characterized by a difference in the color of the base and ends of the hair. The hairline is dyed in one bath with Lowacene dyes in combination with any other acid dyes. After drying, a bleaching composition is applied to the surface and fur is heated. In this case, one dye (Lowacene) is destroyed, and the ends of the hair remain painted over only with the second dye, i.e. there is a bicolor effect. Briza can be dyed both on sheepskin and on long-haired types of fur raw materials: fox, rabbit skins, etc.

Different color effects are achieved by using appropriate acid dyes in combination with spread dyeing. For example, to obtain the “Chinchilla” effect on rabbit skins, they are first dyed blue-gray using Lowacene dyes. Then the upper part of the hair is bleached, after which the composition (gray acid dye) and auxiliary additives are applied with brushes. After drying, rinsing and drumming, black streaks are applied to the hair using a black oxidation dye (Tipping Black).

Obtaining multi-color effects are not limited to the above given examples. A wide range of dyes with different properties allows you to realize any ideas of designers: from a variety of imitations to incredible fantasy options for multi-color dyeing.

Dyeing with reservation of hair ends

In addition to the “Snow Top” effect, there is another option for obtaining a dyed hair base while maintaining unpainted hair ends– the “Frost-effect”. Before dyeing, a special reserve composition is applied to the surface of the hair, which prevents the sorption of the dye. Such materials include, for example, Resist B, which creates a negative charge at the ends of the hair. Due to this, in the subsequent dyeing, the possibility of fixing acid dyes on the protected part of the hair is excluded, i.e. only the hairline base is absorbed the dyes selectively.

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Resist B is applied to the hair with brushes or by spraying. After drying, the operation of ironing is carried out. Then the semi-finished product is dyed with acid dyes (Alizarine) in the presence of an auxiliary substance (Resist Assist ST), which ensures minimal absorption of the dye in the areas of the hair treated with the reserve composition. After dyeing, the skins are processed in the usual way.

Rodol dyes can be used for resist dyeing. In this case, a reserve composition is used that prevents the diffusion of oxidized intermediates into the hair structure.

Dyeing and finishing operations for sheepskins

Fur velour is used for the manufacture of uncovered products. Therefore, special quality requirements for leather materials have been developed. First of all, fur velour should have a smooth velvety pile with a well-defined “writing effect”. This is achieved by the use of appropriate retanning and fatliquoring materials, as well as careful grinding. Another important requirement is a deep (not less than 1/3 of the thickness) uniform coloring of the leather tissue. The paint must be resistant to dry and wet friction, as well as to the action of organic solvents.

Some years ago, fur velour was dyed and trimmed exclusively on leather. Recently, double-sided finishing (“Double face”) has been widely used, in which both the skin tissue and the hairline are intensely colored. It is possible to dye the hair and skin tissue in one color (tone-on-tone), or contrast (bicolor). There are many dyeing techniques that allow you to get a variety of color effects on fur velour. They are based on the general rules of dyeing leather tissue and fur hairline.

Skin tissue collagen and hair keratin interact differently with dyes. Due to this difference certain finishing effects can be created.

The hair has a more compact structure compared to the skin tissue. Therefore, the diffusion of dyes into the thickness of the hair is more

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difficult. The larger the dye molecule, the better the skin tissue is dyed and the worse the hairline is dyed.

The hair is more hydrophobic, therefore it is better painted with dyes that are soluble in hydrophobic media. An increase in the content of hydrophilic groups leads to an increase in its solubility and ability to dye leather tissue.

Thus, the differences between keratin and collagen characterize the affinity for dyes and, therefore, create prerequisites for painting or reserving hair and skin tissue.

Fur velour dyeing with hair reservation

This method aims at obtaining a dyed leather tissue without painting or with a weak shading of the hairline.

Dyeing begins with neutralization. The operation of neutralization is used to eliminate the excessive acidity of the skin tissue.

When dyeing velour with hair reservation, it is recommended to carry out neutralization for two hours with a mixture of formate and sodium bicarbonate in an equal ratio (2 g/dm3). Neutralization is followed by washing with the addition of surfactants that prevent the absorption of dyes by the hairline. Next, the semi-finished product is washed with clean water and sent to the operation of dyeing.

The operation of dyeing begins with the treatment of sheepskins in a 25% ammonia solution (1.5 g/dm3) and an anionic leveler. After 30 minutes, the dyes are added to the solution. For dyeing with hair reservation, Leather and Lowanil dyes can be used. They have a minimal tendency to paint over the hairline. Their recommended concentration in the solution when dyeing in color tones is 2 g/dm3. When dyeing in black tones, the concentration is 3 g/dm3.

To obtain soft leather fabric and to provide a writing effect, the operation of dyeing is used in combination with fatliquoring.

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To ensure the fixation of acid dyes with the collagen of the skin tissue, acid is introduced into the working solution at the final stage.

At the end of dyeing, the operation of washing is carried out in order to remove the dye from the hairline. To get a special whiteness of the hair or to get a pure tone of the hair in case of its weak coloring, optical brighteners are added to the same solution.

Tone-on-tone dyeing

Tone-on-tone dyeing is used to dye the leather fabric and the hairline of fur velor in the same color. Dyeing can be done in a twobath or one-bath method. In the first case, the dyeing of hair and leather tissue is carried out in different baths. First, the hair is dyed using acid dyes and levelers. After dyeing, the hair is washed with clean water, and then the operation of leather dyeing is carried out.

To ensure the purity of the color tone, it is important to create special conditions under which only the hairline would be dyed in the first bath and only the skin tissue in the second one. Therefore, in the second bath, the process is carried out at a low temperature of 32–37 ºC. The affinity of the dye is regulated by the introduction of auxiliary substances in both baths. To dye tone-on-tone, any dyes for leather fabric can be used (Leather, Lowanil, Lowapel).

The dyeing process is combined with neutralization. It is carried out in a solution of sodium thiosulfate with a concentration of 3 g/dm3.

After 1 hour from the start of neutralization, 1.5 g/dm3 of ammonia and a leveling agent are added to this solution. After 30 minutes, a solution of dyes is poured into the bath. The concentration of bath solution is 2 g/dm3. After another 30 minutes, a fatliquoring substance is added into the bath. After 4–5 hours from the start of the process, formic acid is dosed to lower the pH and ensure the dye fixation.

The two-bath dyeing method is time-consuming and laborintensive. It requires large amounts of water and chemicals. However, it

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can be used to obtain any color tone and any color saturation, especially when using a triad of dyes.

The one-bath method is simpler to perform. It is more economical. However, its color possibilities are not as rich as those that can be obtained in the two-bath method. Dyeing of hair and skin tissue in one bath is carried out using special dyes (Solow). The technological process includes neutralization, washing and dyeing. To achieve an intense and uniform

If the temperature is less than 65 ºC, the hair color saturation will be decreased. The semi-finished product is processed in a special solution for 30 minutes. Then dyes are added with a concentration of 2.0–2.5 g/dm3, and after another 30 minutes a fatliquoring substance is added to the solution. An hour before the end of the process, the pH of the solution is reduced by adding formic acid.

Nappalan leather

Until 1970, the “Double face” sheepskin leather (double-sided leather) was processed to produce velour or suede. However, the processed leather was not water-repellent. “Double face” products got wet in rain or wet snow. To increase the water-repellence of leather, producers try to develop new processing technologies. One of the technologies allowed them to create a leather product which was called nappalan.

Nowadays, nappalan leather is used for double-face sheepskins, which have:

•short and uniform sheepskin pile;

•uniform coloring of leather tissue;

•minimal hygroscopicity of leather tissue.

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