Dyeing is one of the major processes in the decoration of leather items. It is the process of permanently changing the colour of leather by the use of a liquid colourant. The core fibres of the leather which are porous in nature absorbs and permanently holds the dye solution. The whole skin can be dyed before it is cut for the production of leather articles or parts of an already produced item can equally be dyed. However, when a whole leather is dyed, there is an even penetration of the dye.
If articles are to be produced before the application of dyes on some parts of the article, it is advisable that holes in products such as belts, straps, etc. must be punched before the application of the dyes since dyes stiffen leather. Also, the dyes will colour and seal the hole edges making them uniform. Dyeing must be carried out before the fixing of any findings such as snaps, rivets, buckles, etc. The leather surface must be free from any foreign matter. The leather must, therefore, be thoroughly washed to improve the dyeing increasing the absorption and penetration rate of the leather.
There are several ways of dyeing leather and leather articles. In this section, the following techniques will be discussed:
1. Whole-hide
2. Reverse or flesh side
3. Induced grain
4. Cross
5. Laminated
6. Lace
1. Whole-hide-
This is the application of the dye liquor on the entire leather. It is important to have enough quantity of the dye that will be sufficient to dye the whole hide. If the dye runs out, it will be difficult to get the same shade of leather even after dyeing the remaining parts with the same colour of the dye. A large dye applicator can be used in applying the dye liquor to cover the entire hide. Another alternative is to immerse the whole hide in a dye bath. After the dyeing, the hide is stretched taut for it to dry.
2. Reverse or flesh side-
This is the dyeing of the flesh side of the leather. Often, the flesh sides of most tanned-dyed skins bought from the shop are left undyed. It is important to dye them, especially if the leather to be used for producing handbag flaps, belts, etc. where the flesh side of the leather will be shown. It must be noted that the penetration of the dye liquor is limited to the flesh side. The dye applicator for oil and spirit solvent dyes must be well bathed in mineral oil. The dye is then lightly brushed across the flesh side of the leather. This gives the flesh side a shallow surface colouring avoiding unnecessary bleeding to the already dyed grain side.
3. Induced grain-
This is the creation of a grained effect on leather by the use of dyes. In this dyeing technique, the dye applicator is left untreated because it gives the best grained effect. One way of creating the artificial grains on the leather surface is by dipping the tips of a heavy sheep wool and gently stroking only the tips across the leather. Another way is using a stiff wire brush to apply strokes across the leather. If the pressing is done hard enough, the bristles of the wire brush will groove the leather and create a textured grain on its surface.
4. Cross-dyeing-
This is the process of dyeing a leather with two colours combined (cross). The first coloured dye is applied on the leather after which the second colour is applied, resulting in a new coloured effect. For instance, red dyed over already dyed leather in the blue dye will give a purpled effect. Other cross dyeing effect includes:
Red over purple= Wine
Red over yellow= Scarlet
Brown over yellow= Light brown
Yellow over dull blue= Blue-green
Pink over orange= Deep orange
5. Laminated-
This is the dyeing of layers of leather to be laminated and used for the production of articles such as necklace pendants, wall reliefs and sculptural forms. Interesting dimensional effects can be created through the dyeing to enhance the general outlook of the articles.
6. Lace-
This is the dyeing of laces. A dye dauber is used in applying the dye liquor on the laces or the laces can be pulled along under the dauber to apply the dye on them. They can also be put in a small container filled with dye for the dye liquor to dye them. If the laces become stiff, they can be rubbed down with saddle soap or Vaseline petroleum jelly.
Dyeing is one of the best ways of enhancing the surface quality of leather products by using coloured dyes to create decorative patterns on them.
