Extraction of Renewable Natural Pigments in Indonesian Cultures for Coloring Batik Fabrics

Abstract

Nowadays, trends of Indonesian batik have increased to replace synthetic pigments with renewable natural pigments (chlorophyll, tannin, and others) due to strong consumer demands for more natural products. Production of renewable natural pigments from plant biomass (e.g., wood wastes) has been developed and produced in liquid, paste, and dry forms. Natural pigment production not only increases their selling-price capacity but should also exhibit biological activities that are environmentally friendly and beneficial for health. Abundant sources of chlorophyll/tannin in wood wastes (including mangrove origins) from forestry industries could potentially substitute for synthetic pigments, which sound environmentally harmful. Wood waste utilization could encourage and create economic opportunities in forest villages, centers of mangrove wood industries, and small/medium-scale batik/weaving enterprises. Natural colors of chlorophyll/tannin seem preferred by coastal and inland motif batik crafters. Accordingly, exploring various natural sources of tannin is essential for fabric/batik coloring, safe for food/beverages, and not endangering health.

1. Introduction

Renewable natural pigments obtained from living creatures/biomass (e.g., plants), such as chlorophyll, tannin, and others, have attracted remarkable attention from the related industry and trade world for coloring purposes (especially textile/batik fabrics, food/beverage packaging, paper, etc). The demand for chlorophyll/tannin pigments tends to increase continuously, as they are renewable, beneficial for human health; seem more environmentally friendly; and also due to the people’s growing awareness of allegedly the possible dangerous compounds in synthetic pigments. Chlorophyll is a complex organic compound containing C, N, H, O, and Mg elements, present in almost any plants (particularly leaves) that functions as a biocatalyst in photosynthesis, whereby CO₂ and water (H₂O) are combined together to produce very simple food (sugar/hexoses). Further, the chlorophyll could exhibit bluish-green colors. Such color appearances could be due to the presence of double bonds (e.g., –C=C– in conjugation or not, –C=O) and unsaturated aromatic rings with N elements [1].

Meanwhile, tannin belongs to polyphenols (with C, H, and O elements), regarded as one of the indirect products of plant photosynthesis, which is formed afterward through assimilation and other complex metabolism processes. Further, tannin is commonly found in particular plant tissues, for example, twigs, leaves, barks, woods, flowers, fruits, and roots. Further, the physiological functions of the tannin presence in the plants are still unknown, possibly protecting the plant tissues against microorganism attacks [2]. The tannin could reveal brownish-yellow to reddish-brown colors, which could be attributed to phenolic, benzene, C=O, and conjugated –C=C– bond groups. Further, such presences in tannin as well as in chlorophyll enable both pigments to absorb light at a particular visible (colored) wavelength range (4000–8000 A), thereby exhibiting various and specific colors [1, 3]. Accordingly, chlorophyll and tannin could play essential roles in the coloring culture of weaving and crafting textile materials (especially the batik fabrics) and others (paper, food/beverage packaging, etc.) in Indonesia.

Batik makers, weavers, and eco-printers can look for chlorophyll and tannins around their homes. Color variations are different for each type and part of the plant, but the performance can be adjusted according to the customer’s order. The presence of natural pigments is often together with other pigments such as flavonoids, anthocyanins, and carotenoids [4].

Chemically chlorophyll contains polar groups (e.g., CHO, Mg⁺² ions, and COO); however, its large nonpolar portions are insoluble in water. Further, plants commonly have two types of chlorophyll (i.e., a and b). Chlorophyll b is more soluble (in water and other polar solvents) than a because the former contains aldehyde (CHO) groups, while the latter is not so. Meanwhile, the tannin is only partially water-soluble, owing to the presence of hydrolyzable (more hydrophilic) structures and condensed/nonhydrolyzable (less hydrophilic) structures in particular proportions. However, chlorophyll and tannin are soluble in alcohols, ethers, and hot water (moreover, with the addition of detergent or alkali).

Regarding other plant pigments (e.g., flavonoid, anthocyanin, and carotenoid), they mostly could be, among others, polyphenols (with highly condensed structures), and the compounds with the presence of double bonds (–C=C– and –C=O) and phenolic groups, as well as macromolecules (with sizable nonpolar portions, despite containing polar groups). Consequently, most of them are insoluble or only partially soluble either in water. However, as occurred to chlorophyll/tannin, those other pigments could be expectedly solubilized in hot water. This is because the hot water could induce more kinetic molecular movement and hence cause more intensive melting of pigments, thereby enhancing their water solubility.

The solubility properties and other characteristics of chlorophyll/tannin as well as other pigments are essential for coloring purposes (e.g., textile/batik fabrics, paper products, and food/beverage packaging). This is because the coloring works, beginning from the pigment extraction (from the plants), the coloring processes, until the finalization, usually employ aqueous liquid media. Further, the presence of double bonds, carbonyl (–C=O), and phenolic groups in those other pigments, as also the case in chlorophyll/tannin, renders them to also absorb visible light at a particular wavelength and hence to appear colored [1, 4]. Further, similar to tannin, those other pigments (e.g., flavonoids, saponine, and anthocyanin) could possibly be formed as indirect products of photosynthesis through further assimilation/other complex metabolisms. The function of those pigments for the plant themselves might be, among others enhancing the plant-tissue durability, releasing specific smells (for the arrival of wanted animals/insects), and attracting the insects to come (especially those in the flowers with their attractive colors) to enhance the plant/flower pollinations. Pollination occurs mostly in the flowers, which refers to the transfer of pollen grains to the surface of the stigma, aiming mainly to develop future seeds. Those seeds would further develop into young plants and ultimately mature plants. As the plants grow mature/older, the reserve food (resulting from photosynthesis) stored mostly in the plant parenchyma tissues might exceed the needs for plant assimilation and other regular metabolism activities. This situation renders the excess food in the parenchymas to be transformed (under no or little oxygen) into the so-called plant extractives, including also the synthesized natural pigments [2].

Communities in forest villages can produce chlorophyll and tannins from plants such as betel nuts (Areca catechu), jackfruits (Artocarpus heterophylla), bananas (Musa paradiciaca), mangroves (Rhizophora mucronata), pine (Pinus mercusii), and Uncaria gambir. Those in the highlands can get it from the tea plant (Camelia sinensis), while those in the lowlands can get it from Rhizophora mucronata, Xylocarpus granatum, Avicenia marina, and Terminalia catappa. Especially in the coastal area are the species of Rhizopora apiculata, R. macrophylla, Pterospermum ferroginum, Ceriops candolleana, etc.

The source of tannin and chlorophyll comes from tree waste which was produced as much as logging forests, amounting to around 928,934.81 m³/year [5]. Another source of log production from plantation forests reaches 40,945,378.90 m³ per year (Ministry of Environment and Forestry of the Republic of Indonesia/Keputusan Menteri Lingkungan Hidup dan Kehutanan, 2018). The source of tannin, chlorophyll, and other pigments mainly comes from the bark of the mangium wood, which can reach 216.49 tons per day or around 9% of logs by weight [6].

Further, wood wastes in the forms of wood slabs, sawdust, barks, etc., are supposedly rich in various natural pigments, such as tannin, flavonoid, anthocyanin, chlorophyll, and carotenoid. So far, those alleged pigment-rich wood wastes are still not utilized optimally, instead just abandoned or discarded. Consequently, the waste utilization into renewable natural pigments could be a better solution/recommendation and hence deserve consideration.

In obtaining/producing renewable natural pigments, after their extraction from plant biomass portions (e.g., barks, woods, roots, leaves, and flowers/fruits) or wood wastes, they could be produced in three forms/shapes (i.e., dry-solid extracts, concentrated pastes, or liquid shapes). Whatever their shapes, attempts should be thoroughly performed, thereby enabling the pigment to meet the standards of quality, security, and uses or benefit principles. Further, the pigment’s raw materials should be consistently available and easily assessed. The pigment products should bear their specification, especially the color standard, color consistency, information about the ingredients as well as other matters added in the pigment formulation, and essentially their shapes. Accordingly, pigment testing deserves to be carried out.

Regarding the shapes/forms of pigment products, however, for the sake of efficiency in long-termed use, especially the trade, it would be better to process/produce the chlorophyll/tannin as dry-solid pigments. Dry natural pigments could last longer or be more durable during storage, rapidly packaged, and easy in case of coloring work/activities (just dissolve them in the water). The essential coloring activities (chiefly for the fabrics/batik) with the pigments, for example, chlorophyll/tannin, consist mainly of mordanting, coloring, and fixating. Mordanting aims to eliminate fat, oil, and other foreign matters, which could adhere or stick to the fabric fibers, thereby otherwise interfering with the fiber-pigment bonds. Also, such elimination could greatly facilitate pigment infiltration/penetration into the pores, voids, or other microscopic fiber structures (micropores/microvoids) during the fabric coloring. Mordanting is usually performed before the fabric coloring, using typol, tawas/alum, tannic acid, and acetic acid/vinegar (all in aqueous solution). Fabric coloring is carried out by immersing the mordanted fabrics in an aqueous coloring-pigment solution (e.g., chlorophyll/tannin). Afterward, the fixation could be conducted, whereby the pigment-colored fabrics are submerged (immersed) in the fixative solution. The fixation intends to strengthen the color fixing at the pigmented fabrics [7]. Further, to examine the pigment performance (e.g., chlorophyll/tannin) at the pigment-colored fabrics, then their color-leaching/fading resistance should be tested against washing, rubbing, and exposure to sunlight, which refers to the recognized standards (e.g., ISO/international standard organization and SNI/Indonesia’s national standards).

Accordingly, research into diverse natural sources of pigments (e.g., tannin and chlorophyll) that are safe for food/drink as well as the human body is crucial for fabric and batik coloring. Relevantly, this chapter presents, elaborates, and assesses the results of exploration, extraction, and application of natural pigments (e.g., chlorophyll/tannin and others) extracted from various plant species/portions/wood wastes and motivation of batik, weaving, and eco-print crafters.

2. Current main situations and elaborated approaches

Natural renewable pigments now become one of the prominent complements in substituting for synthetic pigments for coloring purposes, such that the coloring results become the community’s partial lifestyle. Natural pigments from wherever they come are preferred a lot by consumers (users) because of their superiority, which is inherently exclusive; renewable; environmentally friendly; and appear very typical, distinct, and ethnic, thereby affording high selling values. Natural pigments could become potential superior products regionally and globally. Consequently to achieve such, it is necessary to conduct research in order to get even better results from pigment extracts as well as pigment-colored products (e.g., especially, fabrics/batik, paper, and food/beverage).

The research which have been performed partially revealed that many ethnic groups throughout the world have utilized particular plant species/portions (and vegetation/wood wastes) in natural renewable pigments, including in Indonesia. For such, Indonesia’s ethnic groups have utilized specific plant biomass, among others: ketapang roots (Terminalia catappa L), teak leaves (Tectona grandis Lf.), barks of Rhizophora sp., annato seeds (Bixa orellana L.), tea leaves (Camelia sinensis L), and betels nuts (Areca catechu L), as they feel concerned with securing the environments. Meanwhile, several countries, such as India, Singapore, Malaysia, and China, have conducted intensive research and begun performing the trade transaction dealing with renewable natural pigments because they mostly get attracted to environmentally friendly and renewable products (e.g., plant pigments). Relevant to such favorable achievements, this still needs to be enhanced toward substituting natural pigments for synthetic pigments, as elaborated in the following related essential topics, respectively.

3. Production of renewable natural pigment

In the production aspects, it is essentially related to how renewable natural pigments are obtained. Renewable natural pigments (e.g., chlorophyll, tannin, flavonoid, saponine, carotenoid, and anthocyanin) could be obtained commonly through the extraction process from almost any parts of the plant tissues/biomass allegedly rich in such pigments, for example, tree barks, roots, leaves, fruits, seeds, exudates/saps, and fruit skins [8, 9]. The terms extraction and production are often used interchangeably. In the extraction/production of natural pigments (e.g., chlorophyll/tannin), currently, the particular plant portions considered worth for such are the wood wastes generated abundantly from the tree cutting/felling in the forests and from the wood sawing in the sawmilling industries. So far, those wastes are still underutilized, instead as described before, just abandoned in the forests, merely left accumulated on wood-industry sites, or just burnt uncontrollably, thereby potentially polluting the environment and hence arousing the idea for waste utilization for the production of renewable natural pigments.

Further, those would-be natural pigments (e.g., tannin, flavonoids, saponine, anthocyanin, chlorophyll, and carotenoid), besides already naturally present in the plant biomass or wood wastes, could also be accidentally formed during their heating or storage. This is because during such, chemical and biological changes could occur, such as degradation, depolymerization, respiration, fermentation, and other physiological processes, thereby chemically converting the more complex and higher molecular weight (MW) plant components to simpler and lower MW pigments [10]. Accordingly, those phenomena could also affect or contribute to the pigment productions.

The production of chlorophyll/tannin and other pigments should be preceded by the exploration of the allegedly pigment-rich plants (or wood wastes) which grow or exist in the surrounding community. The simplest way of performing the exploration is through the identification process using specific chemicals. For example, the extracts from the fruits, leaves, and stem barks of mangrove (S. alba) trees, after identification using phytochemical tests with FeCl₃, turned their colors to blackish green or strong blue, which indicated the tannin presence. Still relevant, the barks of S. alba stems, after being dried, maintained their colors similar to those before being dried but then exhibited dry and hard textures [11, 12]. Unfortunately, still, not many of the extracted pigments (e.g., tannin) are ready for use (usable), continuous, and standardized, and nor is their availability in the markets.

To cope with such pigment drawbacks (e.g., its ready use, incontinuity, standardization, and market availability), among the ways, it is necessary to enhance the pigment yields that result from the extraction. This is because the pigment yields are affected by the species origins of the plant biomass (e.g., wood and wood wastes) and the kind of cooking/extracting chemicals. For example, this occurred, when woods of various mangrove species were extracted in hot water (near 100°C), other polar solvents (alcohol/acetone), or aqueous alkali solution (0.5–1.0% Na₂CO₃). It turned out that the extraction using 0.5–1.0% Na₂CO₃ (alkali) afforded higher chlorophyll and tannin yield, viscosity, and solid content than using water. As such, the highest solid content (7.866%) in the tannin was obtained from the woods of A. officinalis, using a 1.0% Na₂CO₃ solution. Meanwhile, correspondingly the highest tannin yield (31.003%) was found at R. apiculata woods [13]. These results indicated again chlorophyll and tannin pigments contained less water-soluble portions, more sizable less-polar structures, and greater molecular weight compounds, which could only be effectively solubilized in hot water or aqueous alkali solution. The data/information about the pigment yields (e.g., tannin) is essential because it is closely related to the pigment potency.

The potency of natural pigments (e.g., chlorophyll/tannin) in particular plants growing at particular area could be predicted from the density of plant stands there (e.g., number of stands per ha; or average biomass weight of the overall stands per ha). As such, as an example, research has been conducted on the tannin pigment in the plant stands that grew on rehabilitated lands at Rembang (Central Java). First of all, the tannin content/yield in the plant biomass was determined (w/w) through a laboratory experiment. Further, by measuring the stand density (i.e., number of stands per ha or stand-biomass weight per ha), then the tannin potency could be approximated/predicted, that is, roughly 105.93 kg/ha/year. Still related, after the third year of stand growth, the tannin potency reached 146.36 kg/ha/year [14]. Consequently, knowing the potency of natural pigments (e.g., tannin) is essential because, further, the tannin contains specific compounds that could potentially exhibit exclusive tastes/smells.

Among such exclusive tastes/smells is that the tannin could render its compounds to taste bitter and astringent, which could be toxic, thereby besides protecting the plant tissues against organisms (as presumed before), also decreasing the plant digestibility and hence deterring the scavenging herbivores and other pests to consume them. Such bitter/astringent tastes are often found in young fruits. Changes in tannin compounds could exert a significant role in fruit ripening. Accordingly, it is strongly alleged physiologically, perhaps that tannin serves as plant-growth regulator. Further, tannin content in the plant biomass (e.g., slabs, twigs, and woods), inadvertently dissolved and leached by the rainwater (with various kinds of humus), renders the colors of the flooded/stagnant water in the swamps or peat marshes to appear blackish brown like those of tea water, popularly known as black water. The tannin also causes bitter/astringent tastes and imparts dark brown colors to the tea water.

Relevantly, imparting the colors by natural pigments (e.g., tannin/chlorophyll and others) at the fabrics (e.g., batik) should proceed in stages. This is because most of the pigments are, as described before, insoluble or only partially so in the water. Therefore with stages, it could render the pigments more water-soluble. Moreover, in the coloring works, as has been described, it employs mostly aqueous liquid media. The first stage in the fabric coloring (after the fabric cleaning and mordanting) starts with immersing the cleaned/mordanted fabrics in the aqueous pigment solution, followed by the fixation stage. In this stage, the pigmented fabrics are fixated with specific inorganic salts such as kapur/lime (CaCO₃), tawas/alum (Al₂[SO₄]₃), and tunjung/ferrous sulfate (FeSO₄). Fixing agents direct chlorophyll and tannins into light or dark colors and are more resistant to washing, sun exposure, and ironing. The common procedures in coloring the fabrics are as follows: 50 grams of any chemical fixatives (lime, alum, or tunjung) are dissolved in 1 liter of water. The resulting fixative solution is then allowed to settle/precipitate for 24 hours until two layers are formed (upper and lower). The upper/supernatant layer is further used as the fixative solution. The fixation is performed by immersing the pigmented fabrics in the fixative solution for approximately 15 minutes. Afterward, the fabrics are removed, allowed to dry, and ready for color detection. As such, the dried fabrics are immersed again in the specific color-detecting aqueous liquid. The color detection/identification test procedures refer to the RHS (royal horticultural society) color charts. Afterward, the color-identified fabrics are properly documented by inscribing specific labels, such as kinds of pigments, kinds of fixatives, appearances of the imparted colors, 2022.

As of this occasion, despite strenuous attempts in imparting various pigment colors/motifs at the materials (e.g., fabrics) with the fixative aids, unfortunately, those available varying sources of renewable natural pigments which are abundant in Indonesia and more environmentally friendly have not yet provided maximal solution, especially as a substitute for synthetic pigments. Further, in spite of strong suggestions and appeals for Indonesia’s batik crafters/weavers to use natural pigments, based on such positive allegations, pitifully, in fact, the majority of domestic batik crafters/weavers still use synthetic pigments. Accordingly, systematic and thorough attempts deserve carried out to reduce the dependence on imported synthetic pigments, among others, by establishing renewable natural pigment industries that utilize chlorophyll (green), anthocyanin (red-violet), xanthophyll (yellow), tannin (brown, reddish brown), and carotene (orange), which are abundantly available or existed in the plants.

Further, in order that Indonesia’s abundant natural pigments could be obtained and produced into usable or ready-for-use pigments in feasible operation (technically as well as economically), then it is necessary to explore the genetic and biochemical aspects of the sources of natural pigments (especially the plants), which can bring essential economy values. Accordingly, a breakthrough is urgently performed with respect to the effectiveness, efficiency, and rules to regulate the utilization of those natural biopigment sources. In addition, the involvement of the batik-crafting community and traditional fabric weavers should get a priority. The aims are that the pigment-industry continuation and environment sustainability could be realized.

4. Variations in colors and motifs at batik fabrics

Batik fabrics are one of the pigment-colored and motif-decorated products. As such, the traditions performed by the batik crafters and fabric weavers to impart the fabric colors and motifs using natural pigments are by cooking (boiling in the water) the plant biomass (e.g., barks, leaves, wood slabs, sawdust, and flowers), until the colors appear in the boiled water (as pigment solution). When the colors become thickened or viscous enough, the fabrics are immersed in the pigment solution to undergo the coloring, as systematically shown in Figure 1. These local coloring procedures are conducted a lot by the forest village’s community, which further become a guidance/reference, adopted by consecutively the regional authority, Indonesia’s state-owned forest enterprise (Perhutani) in Central and East Java; and wood enterprises in Kalimantan, Sumatra, Nusa Tenggara, and Bali.

Figure 1.

Illustration of coloring the fabrics, using the pigments extracted from consecutively leaves dan barks of avocado (Persea americana Mill), jambu seeds (Psidium guajava L.), mahoni (Swietenia mahagoni; Jacq), manggous (Mangifera indica L.), and coffee (Coffea arabica L), (using the fixatives: Alum, lime, and ferrous sulphate).

The colors of natural pigments (e.g., chlorophyll, tannin, and others) become essential to seek and arrange the motifs at the pigmented fabrics, which should be compatible with the desires of the batik/fabric crafters; and also with the tastes of the ordering users/consumers. If we want motifs other than chlorophyll and tanning pigments, we can use waste from plant species or other sources of wood waste. Plant biomass and wood wastes produce a variety of colors. The leaves were dominated by chlorophyll can create green. The presence of flavonoids can create yellow. If tannins dominate the leaves and bark, they give brown, brownish-yellow, or reddish-brown [15, 16].

The varying colors imparted by those several kinds of natural pigments should be confirmed more convincingly with regard to the pigment source origins and their positive presence. As such, source origins that cover tree roots, barks, stems, and leaves from mangrove (Avicennia sp.) plants are prevalently very rich in chlorophyll, tannin, phenolic, and flavonoid compounds, where their presence is indicated, after the detection tests, by a strongly positive category [++] to a very strongly positive category [+++] [17, 18]. This implies that if a part of those mangrove plants is dissolved in hot water, then the resulting colors could appear very strong, that is, blackish brown, resembling the tea-water colors. The presence of particular pigments (e.g., chlorophyll, tannin, and flavonoid) with high content in mangrove plant parts allows the extracts to be used as a natural pigment for fabric coloring.

Besides mangroves, other plant species (e.g., old teak trees) could also exhibit specific colors, which were due to the presence of extractives, predominantly 2-methyl anthraquinone (as polyphenols), where its content was quite great (reaching 13.54%). In teak wood, the quinones together with wood lignin allegedly enhance wood durability and also imparts attractive appearance/color to wood surface as well as seemingly renders easier the wood working (e.g., sanding, planing, and polishing) into favorable teakwood products [19]. However, the teak extractives contained tannin only a little [20, 21]. Further, the tannin content in the extracts from Acacia mangium barks could reach 15–20% [22]. The batik fabrics which were colored with Acacia amngium’s tannin, were resistant against the high-intensity sunlight and also against the pH changes [15].

Likewise, coloring the cotton fabrics with the extracts from teak (Tectona grandis) leaves, previously mordanted with alum and acetic acid (vinegar) separately, brought the fabrics with different color motifs, expressed in brightness values, that is, 55.56% (less bright) and 77.22% (brighter), respectively [23]. On other occasions, chlorophyll and tannin pigments were extracted from the barks of Acacia mangium, three mangrove species (Terminalia catappa, Rhizophora apiculate, and R. mucronata), and Tectona grandis, and then used concurrently for fabric coloring, followed with the fixation (using alum, lime, and ferrous sulfate, separately). It turned out that these procedures that incorporated chlorophyll and tannin could be used either as basic color motifs or as supplementing the colors of the resulting batik fabrics [24, 25, 26]

In imparting the fabric colors, it turned out that tannin is the most dominantly used in batik fabrics. Also, tannin is used in the coloring aspects and the color variations, where the two latter cases are the most important in designing and developing the batik colors and motifs, especially the inland motifs [27]. On other occasions, research results revealed that different colors in the colored fabrics could occur using particular pigments due to the use of different fixatives. This case was commensurate with the previous statement that the appearance of different colors in the pigmented fabrics could be due to different fixatives. The fixative use actually aimed to strengthen the bonds of fabric-fibers-to-pigments.

Further, research results in using a fixative solution, after the batik-fabric coloring, revealed that the fabric colors would not easily fade or leach out and become more resistant to rubbing/ironing [25]. The fixatives used in this research consisted of tawas/alum, kapur/lime, and tunjung/ferrous sulfate. Those three fixatives were used because they had been utilized a lot; moreover, the fixative prices were affordable, inexpensive, and easily obtained in the markets. Meanwhile, the natural pigments used for such were the chlorophyll and tannin extracts from Acacia mangium and two mangrove species (Terminalia catappa and Rhizophora apiculate).

Relevantly, tests have been conducted on 73 plant species, which supposedly could serve as natural pigment sources. It turned out 26 species were identified containing natural pigments (allegedly tannins) that imparted yellowish brown, reddish brown, or strong brown colors for basic colors of batik fabrics [1, 13, 14, 28]. Those tannins originated from the particular parts of those 26 species, such as leaves, barks, flowers, and twigs (Table 1).

No	Species of the plant	Parts of the plants	Colors imparted/appeared on the fabrics
1	Acacia mangium	Tree barks, leave	Strong brown, green
2	Areca catechu	Fruits, leave	Brown, reddish-brown, green
3	Artocarpus heterophylla	Tree barks, leave	Yellowish-brown, green
4	Bixa orelana	Tree barks, leave	Blackish-brown, green
5	Caesalpinia sappan	Tree barks, leave	Brown, Yellowish-red, green
6	Camelia chinensis	Leaves, tree barks	Green, Reddish-brown
7	Ceriops candolleana	Tree barks, leave	Yellowish-brown, green
8	Cudraina javanensis	Tree barks, leave	Reddish-brown, green
9	Garcinia mangostana	Fruit skin, leave	Brown, reddish-brown, green
10	Morinda citrifolia	Barks, leave	Brown, reddish-brown, green
11	Pterocarpus indicus	Tree barks, leave	Red, yellowish-brown, green
12	Koordersiodendron pinnatum	Leaves, twigs	Strong red, brown, green
13	Musa paradiciaca	Flowers, fruits	Brown, blackish-brown, green
14	Peltophorum pterocarpum	Tree barks, leave	Brownish-red, red-black, green
15	Pinus mercusii	Tree barks, leave	Reddish-brown, green
16	Psidium guajava	Tree barks, leave	Greenish-brown, green
17	Rhizopora apiculata	Tree barks, leave	Brown, blackish-brown, green
18	Rhizopora mucronate	Tree barks, leave	Blackish-brown, brown
19	Soneratia alba	Tree barks, fruits	Brown, greenish-brown
20	Syzygium conglomeratum	Tree barks, leave	Brown
22	Swietenia mahagoni	Tree barks, fruit skins	Brown, red, yellowish-brown
23	Terminalia catappa	Tree barks, leaves	Brown, black, brownish-yellow
24	Tectona grandis	Leaves, tree barks, woods	Red, brown, blackish-brown
25	Uncaria gambir	Leaves, twigs	Strong red, brown
26	Xylocarpus granatum	Tree barks, fruits	Brownish red, brown

Table 1.

Parts of the particular plant species, regarded as sources of tannin’s natural pigments for coloring the batik fabrics and other woven fabrics.

Sources: Jamal [29]; Basri et al. [30]; Saefudin et al. [1]; Susanto (1980); Prayitno et al. [28], Poedjirahajoe et al. [14]; Suhendry et al. [13]

The natural pigments (i.e., tannin) extracted from the root parts of those particular plant species (Table 1) for fabric coloring, then treated with three different fixatives (tunjung, alum, and lime) brought the fabrics with three different colors. As such, after being fixated on tunjung, the fabric colors appeared dark, in average black to gray colors. Meanwhile, correspondingly after being fixated with alum, the fabric colors became brighter than the original pigmented-fabric colors (without fixative treatment). Likewise after lime fixation, the pigmented-fabrics generated blackish colors [27].

The dark/blackish colors (Table 1) appearing at the pigmented fabrics (after tunjung fixation)) indicated that a reaction occurred between the fixative and tannin pigments (plant extractives) that produced complex salts. The complex salts, being large-sized compounds, could additionally provide a bridging (intermediary) between the pigment and the fabric fibers, thereby further creating strong fiber-pigment bonds (fixing) and, accordingly, imparting strong color adherence at the pigmented fabrics. Meanwhile, the different colors (not dark/blackish colors, but brighter colors) of the pigmented fabrics after the lime as well as alum fixations, supposedly did not produce complex salts, thereby rendering the fibers-pigment bonds not too strong. However, the lime as well as alum fixatives, could afford ionic bonding with either fabric fibers or pigments, thereby still imparting the fabric-pigment bonds, although not so strong as the bonds exerted by the complex salts [31].

Further, it appeared that the use of different fixatives (i.e., alum, lime, and tunjung/ferrous sulfate) separately at particular fabrics brought the pigmented fabrics with the colors toward the brightest, then less brightness and ultimately the darkest, respectively (Table 1). In another case, different kinds of fabrics consecutively with cellulose-based fibers (i.e., mori, cotton, and cotton yarns) and with protein-based fibers (wool), but colored with the same natural pigment and then treated with the same fixatives, brought the pigmented-fabrics with different colors. This difference occurred because mori/cotton fabrics and cotton yarns comprise mostly cellulose polymers, thereby rendering the fabric/yarn fibers to easily adsorb the pigments and fixatives. However, the wool (as the animal/sheep hair fibers) comprises mostly protein polymers, which could have different characteristics in interacting/adsorption with the pigments/fixatives. Accordingly, cellulose-based fabrics/yarns are widely used as pigment-colored media by batik crafters/weavers [32].

5. Opportunities and challenges

Several batik and eco-print artisans in Central Java and Yogyakarta have started cultivating, producing and selling natural chlorophyll and tannin pigments commercially. Available dry extracts include: Indigofera tinctoria, Camelia chinensis, Intsia bijuga. Other plants that are also rich in natural pigments (tannin and chlorophyll) are soga tingi (Ceriops candolleana), tegeran (Cudraina javanensis) and noni (Morinda citrifolia), jambal (Pelthophorum ferruginum), kesumba (Bixa orelana), and guava (Psidium guajava) (Susanto, 1980; [1]). Although those extracted natural pigments have been known a lot by fabric crafters/weavers; unfortunately, only a few have utilized them. The main obstacles for such few users are the limitation of pigment varieties that are ready for use (usable), lack of the crafter/weavers’ knowledge about pigments’ raw materials, and insufficiency in ready-for-use technology. Besides, the availability of natural pigments is affected much by the seasons, environments, and collecting workers, thereby causing a not-continuous pigment supply to the crafters/weavers. Despite their drawbacks, the natural pigments could prospectively afford high market potencies as Indonesia’s superior commodity to enter into the global markets due to their attractiveness with unique, ethical, and exclusive characteristics. Those pigment drawbacks and prospects could become notable challenges for the batik crafters and related researchers.

The challenge for the researchers is that it is necessary to explore the natural pigment sources ready for use. The creativity of fabric crafters/weavers to seek fabric motifs that should conform to the user’s tastes and desires could become their own problems. These classical problems also occur to the producers of batik and other woven fabrics scattered in many Indonesia’s provinces. The batik crafters should obtain pigment-rich plants, which are fast growth, shortages, enormous available, and easily obtained in their home vicinities. To obtain the plant species rich in natural pigments with such favorable plant-growth characteristics necessitates thorough development for the present or future.

The development of natural pigments in the future should focus on research in the design motifs to anticipate local and global markets. Kinds of laboratory researches that use experiment methods should try hard to invent efficacious/unique formulae to develop such pigments in the crafter-community vicinity. Commonly, natural pigments are obtained/extracted by cooking the plant biomass/wood wastes in hot water (near 100°C). Further, to make the colors of the pigmented stuffs (e.g., fabrics) last long or as color protection against fading/leaching, it should use fixatives (alum, lime, tunjung, etc.). Plant biomass and wood wastes are allegedly rich in natural pigments (e.g., tannin/chlorophyll, anthocyanin, xanthophyll, and quinone). Evaluation results alleged that tannin’s natural pigment was the most prospective for coloring purposes (e.g., fabrics).

Despite the reported success/prospects of using natural pigments (especially tannin), the data and information about the pigment potency (e.g., from forests/wood wastes) are still lacking or inadequate and have not yet been assessed. Furthermore, using tannin as a natural pigment from forests/wood wastes could become an added value for the tannin’s plant sources and essential information for the community who love Indonesia’s batik fabrics and other woven materials colored with the tannin.

The plant tannin, besides already being intended as fabric coloring, has long been widely used as a tanning agent to convert animal bones and skins into leathers (under high temperatures), which are stable, strong, and elastic/flexible. The tannin, as high molecular weight polyphenols, contains numerous OH and other polar groups (e.g., CO and COO) and is, therefore, able to impart multiple strong hydrogen bonds not only with fabric fibers but also with hydroxyl/other polar groups at the bone/skin proteins. Tannin presence in the plant leaves is concurrent with the chlorophyll presence, thereby allegedly causing the changes in leaf colors. The leaves of whatever plant species could also undergo the color changes sooner or later because the leaves perform a double function. As such, the leaf chlorophyll absorbs the red and blue colored light from the sunlight while concurrently conducting photosynthesis. Then, gradually reducing the capacity of chlorophyll to absorb sunlight, reducing the intensity of the green color of the leaves, until they become old, dry out and finally fall. Meanwhile, the carotene that imparts red colors to the leaves is more stable than the chlorophyll, thereby enabling the leaf’s reddish-orange colors to stay longer, although the leaf’s green colors disappear [33]. Other factors that could affect the pigment stability (e.g., their colors) of cations, oxygen, pH, sulfur dioxide (SO₂), proteins, and enzymes. All factors should then be considered.

Considering such, it is essential to know that the attractive varying colors imparted by plant’s natural pigments (e.g., chlorophyll, anthocyanin, flavonoid, carotenoid, etc.) have attracted enthusiastic attention among many genetic experts. This is because such pigments might have meaningful relations with the various morphology aspects in plant species (but in the same genus), which are still close relatives. That information is essential for the taxonomist to determine and combine the plant’s evolution lines into one group. Regarding flavonoid pigments, their form in the plants could be induced by the blue-colored light radiation (e.g., from the sunlight) to increase the plant resistance against ultraviolet radiation.

6. Conclusion and suggestions

Indonesia is endowed with abundant availability of renewable and environmentally friendly natural pigments, with respect to their huge potencies, numerous pigment kinds (e.g., tannin, chlorophyll, flavonoids, saponine, anthocyanin, and carotenoid), and their varying colors (e.g., green, red-violet, yellow, brown, reddish brown, and orange). Expectedly those could serve as substitutes for synthetic pigments, which are mostly environmentally unfriendly.

Those natural pigments could be obtained from almost any part of the plant biomass (e.g., tree barks, roots, leaves, fruits, seeds, exudates, and fruit skins) and wood wastes through commonly the extraction process, which is further beneficial for imparting colors and motifs to, for example, specially woven fabrics/batik, paper products, and food/beverage packaging, commonly performed by the synthetic pigments.

Unfortunately, the majority of Indonesia’s users/consumers still use synthetic (inorganic) pigments, which are mostly imported. One way to overcome such is by establishing industries to produce natural pigments, which could last longer and be ready for use. Accordingly, the natural pigments (as the pigment-colored products, e.g., batik fabrics) should incorporate the fixation process (to strengthen the fabric fiber-pigment bonds), using, for example, alum, lime, and tunjung/ferrous sulfate fixatives); and undergo the quality tests (among others the color resistance against the leaching/fading, due to mainly the detergent washing, rubbing/ironing, and sunlight exposure).

The success in utilizing the plant biomass and wood wastes into pigments, which are not only confined to chlorophyll and tannin (currently the dominant natural pigment for especially batik coloring and tanning agents), but extended to others (flavonoids, carotenoid, anthocyanin, etc.), could be beneficial and safe for health, thereby expectedly encouraging and creating economic opportunities as well as welfare, for example, pigment industries in small/medium and large scale levels, users/consumers, and enthusiastic community.