Leather pigments are for dyeing and coating of leather surfaces, so that leather has a variety of colors and effects. Due to the affinity to leather, leather pigments can be used for leather coloring. Acid, medium, direct and alkaline pigments are applicable to leather products. Neutral pigments are used the most commonly in spraying. Pigments should also be slightly soluble in water and easily soluble in organic solvents such as ethylene glycol, ether, ethanol or dimethylformamide. Leather pigments are mainly sprayed to color pigskin, cowhide, sheepskin and other types of leather.
Reflective Powder
Thermochromic Pigment
Photochromic Pigments
Pearl Powder
glow in the dark pigment
chameleon powder
UV Powder
Mica Pigment
Before leather pigments are applied, leather should be cleaned to remove oil stains, dust and debris on the surface. If necessary, leather can be cleaned with leather detergent. In addition, appropriate brushing tools and glue are required.
For even distribution of pigments, the brushing direction and sequence should be correct. If multiple layers of pigment are applied, the following layer should not be applied until the previous layer is dry. In addition, attention should be paid to the stability and use of leather pigments.
Leather pigments should not be used in poorly ventilated place. Moreover, attention should be paid to the stability and use of leather pigments, in order to avoid deterioration or expiration.
Step 1: Material collection
Materials required for leather pigments: alcohol, vinegar, carbon black, rhizome, bark, etc. hese materials can be purchased in the market, or collected in the natural environment.
Step 2: Preparation of pigments
There are two methods to prepare leather pigments: blow-in and dipping. In the blow-in method, materials are mixed with melted fat and boiled over the fire of a furnace. Then leather is directly immersed in pigments. In the dipping method, pigments are dissolved in hot water, and then dry leather is kept in pigments for some time.
Step 3: Adding of other materials
Other pigments can be added for leather coloring and aroma, such as herbal pigments, natural pigments, vegetables, etc. They are added as needed to control the color, strength and aroma of leather during production.
Step 4: Leather soaking
Leather is colored by soaking in pigments for some time. All leather should be fully soaked to even colors.
Step 5: Additional processing
At the end of leather dyeing, additional processing may be performed for better color or texture. Leather can be treated before or after dyeing, such as rubbing with stone or grass. Additional processing will lead to better possibility, flexibility and freedom.
Main differences between leather dyes and pigments:
Solubility and dispersibility
Leather dyes are soluble in solvents or water. They can penetrate at the molecular level into fibers or substrates. Chemical bonds are formed due to interaction between leather dyes and fibers or substrates. Leather pigments are granular substances, which are insoluble in solvents or water. They are often suspended in media.
Permeability and adhesion
Leather dyes have good permeability. They can penetrate into fibers or substrates, so that leather is dyed as a whole. Leather pigments are mainly adhered to the surfaces of objects. Their particles do not penetrate into objects.
Transparency and covering power
Due to molecular penetration into fibers or substrates, leather dyes have high transparency. They do not fully cover the primary colors of objects. Leather pigments have high covering power, which can fully cover the primary colors of objects.
Durability and stability
Leather dyes can form chemical bonds through interaction with fibers or substrates, so they have lasting dyeing effects. They are also resistant to light, water, washing, etc. Leather pigments are relatively weak in durability and stability. They are susceptible to the effects of light, water and chemicals.
Water-based leather pigments are environmentally friendly. Compared with conventional organic solvent-based pigments, water-based leather pigments feature higher safety, less contamination and better coating effects. They are similar to conventional organic solvent-based pigments in use. But water-based leather pigments should be applied with suitable tools and methods.
With organic solvents as diluents, organic solvent-based leather pigments are widely applied in coating and dyeing of leather products. The use and precautions for organic solvent-based leather pigments are similar to those for water-based leather pigments.
Metallic leather pigments are for metallic leather effects, so that leather have a metallic gloss. The use of metallic leather pigments is similar to that of other leather pigments. But attention should be paid to the stability and use of metallic leather pigments.
The covering power refers to the ability of a pigment to cover the primary colors of objects, thus avoiding exposure of primary colors. It is usually calculated by the amount (in mg) of leather pigment per one square meter of a surface. It depends on the difference between the shading coefficient of a pigment and refractive index of a film forming agent. The greater the difference, the higher the covering power is. The covering power of a pigment is also dependent on the light adsorption of a pigment. Carbon black has high covering power due to no adsorption of light.
The coloring power refers to the coloring ability of a pigment after mixing with another pigment. For example, if a grey color is made by mixing two kinds of carbon black with one coloring pigment, the amount of white pigment varies greatly. If more white pigment is added, the coloring power will increase.
The fineness has a great influence on the mechanical strength of coating, but has little impact on the coating weight. At present, the fineness of leather pigment paste is determined by many methods. It is usually determined with a rubbing board.
The oil adsorption capacity of a pigment refers to the minimum amount of oil for full adsorption of 100 portions of leather pigment paste. The finer the leather pigment paste at the same weight, the more particles, and the more oil is required.
The light resistance refers to the resistance of a pigment to light or the ability to gradually fade and discolor. Some leather pigment paste has lower light resistance, due to changes in chemical reaction or structure. This may also be caused by harmful substances in pigments.
Coated leather is usually ironed, so pigments should have high heat resistance, to avoid discoloration in ironing and polishing. Ironing of leather clothes is relatively difficult in color change, due to unknown heat resistance of leather pigment paste in post-treatment.
Other factors affecting leather features: cold resistance, migration resistance, specific gravity, purity, impurities and other factors of leather pigment paste. The specific gravity of pigments affects its settling rate in diluted color paste. If a finishing agent is applied, the pigment with lower specific gravity usually floats on the finishing agent solution, while that with higher specific gravity is prone to settlement. In this case, full stirring is required.
There is dye wastewater in the use of leather pigments. Due to a lot of organic matters and pigments, dye wastewater will cause serious pollution to the environment. It is treated by physical, chemical and biological means, such as precipitation, filtration, adsorption and biodegradation. Effective treatment can reduce pollution and recycle valuable substances.
Leather pigments may be toxic. They mainly contain heavy metals. Heavy metal poisoning may occur after long-term exposure. Therefore, operators must wear protective clothes while using leather pigments, including personal protective equipment such as gloves, masks and goggles. In addition, follow the precautions below:
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