Batik, or wax resist dyeing, is a method to dye the cloth using wax as color barrier. Research about Batik Method dyeing used in tanned leather media is rarely conducted. The change of the use of media from cloth to tanned leather in the Batik Method dyeing has caused many troubles which require the solution. Especially, the process involves stages such as wax adherence, dyeing, and wax release.
Tanned leather dyeing technique, according to Burkinshaw and Paraskevas, is using tanning drum, spray and brush. The dyeing with this technique only produces one color without motive, and then, the motive depends on the original leather. The advantage of Batik Method dyeing compared to general tanned leather dying is that it produces various motives on the surface of tanned leather and with various colors. Tanned color dyeing with Batik Method is applied to cow leather with vegetable tanning, to goat leather with combination tanning, and to rabbit leather with chrome tanning.
To produce the satisfied Batik Method dyeing, it depends on the composition of Batik wax and the selection of dyeing agent. The adherence rate of Batik wax agent to the tanning leather is influenced by some factors. Heated Batik wax temperature, Batik wax composition, and leather surface texture. Wax temperature has very dominant influence on the incoming wax into leather tissue. The more Batik waxes are absorbed into chorium layer of leather, the more difficult it is to detach.
Batik wax detaching process is successful if all waxes are solved without the influence of color and leather strength .The detachment of wax from leather may be using hot alkali solution and may be natrium silica for silk media. The physical characteristics of Batik wax, including melting point, adherence rate, penetrating rate, and freezing speed, are influenced by the comparison of the composition of Batik wax mixing materials such as paraffin wax, beeswax, resina colophonium and animal fat.
In other side, leather thickness differs from cloth, and the leather is consisting of three layers such that the penetration of dyeing material into leather is very determining the success of leather dyeing. The selection of dyeing type for Batik Method dyeing on leather is relying on chemical structure between dyeing and leather, tanning type and the presence of chemical active substance on leather surfac.
Chrome tanned leather with thickness of 1.2-1.5 mm and 3.6 % chromium oxide are supplied by a Tannery located in Yogyakarta. Indonesia. Auxiliary chemicals such as Leathernol SPU (fat liquor), Tanigan TAK (retaining agent) and chrome tanning agents are obtained from commercial sources. Batik Wax made by a mixture of materials such as paraffin wax, beeswax, resina colophonium and animal fat are supplied by Research and Development House of Leather, Rubber and Plastic Goods Industries. Yogyakarta. Indonesia. The four following commercial dyes were supplied by LIK Magetan. Indonesia with different chemical structures:
– Acid black 210 (anionic dye)
– Indigozol blue IBC
– Remazol back 5
– Napthol AS
3.1. Mixing Batik Wax The mixture of Batik Wax includes paraffin wax, beeswax, resina colophonium and animal fat. Mixing Batik Wax is by melting resina colophonium because it has the highest melting point (700C). It is followed in order by melting paraffin max, beeswax, and animal fat which has the lowest melting point. The variable of research is the difference of ratio between resina colophonium and animal fat (A = 2.5 : 10 ; B = 5 : 7.5 ; C = 7.5 : 5 ; D = 10 : 2.5).
3.2. The Tanning and Dyeing of Batik Method The tanning and dyeing of Batik Method are completely explained in Enclosure 1. 3.3. Testing and Measurements Batik wax test has adherence rate, freezing speed, melting speed and melting point measured based on AOAC Procedure. Batik Wax Penetration is assisted by Hitachi TM 3000 Table Top and examined Scanning Electron Microscope. Degree of penetration wax is calculated along cross-section of Batik Wax sample with 300 x magnification.
% penetration from grain side = VZ / VX x 100 %
Fastness testing for leather batik samples was tested according to ISO standard methods. The specific tests were: ISO 105-X12 (1987), color fastness to rubbing; ISO 105-CO2 (1989), color fastness to washing; and ISO 105- E04 (1989), color fastness to perspiration. The test of the quality of tanned leather Batik is measured based on SNI Standard which involves stitching strength of SNI 06-1117-1989, pulling strength of SNI 06-1795-1990, stretching strength of SNI 06-1795-1990 and leather fainting of SNI 06-4085-1996.
4. Results and Discussions
4.1. The influence of the ratio of resina colophonium to animal fat on batik wax quality
Table 1 indicates that the different ratio of resina colophonium to animal fat will influence adherence rate, melting point, melting speed and freezing speed of batik wax. The highest adherence rate of the wax is found at ratio of resina colophonium to animal fat of 10 : 2.5, while the lowest adherence rate is obtained at ratio of 2.5 : 10. The adherence rate of batik wax is greatly influenced by the rate of resina colophonium material. The more resina colophonium is used as the mixture of batik wax, the stronger adherence rate of tanned leather is given by resina colophonium containing the monomer of resin acids. These resin acids are the derivate of diterpenoid- monocarboxylate from hodrypoenanthren alkyl, which has molecule formulation C20H30O2 . Figure 1 explains SEM of grain leather surface penetrated by batik wax. Indeed, batik wax containing monomers of resin acids will lift some epidermis layer and open collagen fibril such that the monomer of resin acids penetrates into tanned leather. The depth of penetration during the adherence of batik wax into tanned leather depends on ratio of acid monomer to other material mixture. At high ratio of resina colophonium to animal fat, the penetration rate reaches 21 % of leather grain thickness.
Figure 1: The photo based on Scanning Electron Microscope of cross-section of batik wax on leather
Figure 2 explains the ionic bonding between batik wax and tanned leather. Resina colophonium contains monomer of resin acids, with the highest proportion contributed by abietate at 63.4-70.3 %, while the remaining includes sandarakopimarat acid, dehydroabietat acid, and isopimarat acid. In figure 2, there are compound bonding and carboxylate cluster from abietate ester methyl which is the functional cluster of resin monomer, which binds chrome on tanned leather with ionic bonding. Carboxyl cluster in the abietate ester methyl hydrophobic monomer is functioned to release H+ ion such that there is ionic bonding with chrome. Next, it forms a very stable bonding with chrome tanned leather and polymerizes with monomers contained within resin composite such that it produces stronger adherence rate.