Description:FIELD OF THE INVENTION
Present invention relates to a natural indigo paste and method of its application in printing and hand painting. Present invention more particularly relates to an indigo paste and a method of printing using the same, in which the reducing agent used is 100% natural. The indigo paste and the method utilizing 100% natural reducing agent made it possible to use the natural indigo in screen printing, block printing and hand-painting and to achieve darker shades. Use of 100% natural reducing agent retains the indigo paste used for printing in its reduced state for longer period of time which is of the order of one month, making it possible to store it for a longer period of time. The natural indigo paste does not require reduction after application of print.
BACKGROUND OF THE INVENTION
Synthetic dyes are widely used for coloring a variety of materials, despite their well-documented negative environmental impact. While improving current dyeing methods to make them more efficient and eco-friendly is essential, promoting the use of natural dyes offers a sustainable alternative for the dyeing industry.
The practice of indigo hand block printing has a deep and ancient legacy that stretches across thousands of years. This rich blue dye, derived from the leaves of the indigofera plant, has been embraced by numerous civilizations around the world. Its use dates back to early societies such as those in India, Egypt, and Mesopotamia. However, it was in India that the craft of indigo dyeing and block printing truly flourished, reaching remarkable levels of artistry and skill. The process of indigo block printing is intricate and demands both expertise and precision. These textiles are deeply embedded in India’s cultural heritage and have become timeless symbols of tradition, identity, and sustainability. In recent times, indigo hand block printed fabrics have seen a revival, driven by the rising demand for sustainable, handcrafted fashion. Designers are now integrating these fabrics into their luxury collections, blending heritage craftsmanship with contemporary style, whether in small-scale or large-scale production.
Natural indigo, sourced from Isatis tinctoria, serves as a bio-based substitute for chemically synthesized indigo. However, due to indigo’s insolubility, it must first be converted to the water-soluble leucoindigo form for dyeing, traditionally achieved through the sodium dithionite vat method, which involves harsh chemicals. Throughout the dyeing process, indigo undergoes several transformations between its soluble leuco form and the insoluble oxidized form. The oxidation process can be difficult to manage, and traditional vat methods often require additional reducing agents to keep the dye soluble. Ensuring the solubility of indigo throughout the process could simplify dyeing, reduce steps, and minimize the reliance on harmful chemicals
So far in the industry the natural indigo paste has been used in block printing more often than screen printing or hand-painting, with caustic soda as a reducing agent. Some recipes also use thiourea dioxide as a reducing agent. Indigo paste has also not been used extensively because of the lack of practicality in the printing process. This is because the paste needs to be in a reduced state while being printed and should only oxidise once it is on the fabric, otherwise the colour fastness will be very poor and the print will fade and wash off. Since the reduction capacity of caustic soda deteriorates quickly when in contact with water (and the pigment paste contains water), the paste loses its reduced state very quickly and the paste needs to be reduced constantly. Due to this cumbersome process the artisans do not widely use natural indigo for printing. The blue colour in block printing is more widely achieved with a chemical pigment.
The caustic soda method allows the paste to be in the reduced state only for a few minutes. This is because the reduction action of caustic soda deteriorates when in contact with water. Hence the paste needs to be reduced constantly, for which caustic soda needs to be added regularly, which increases cost, labour and the use of chemicals. It also interrupts the fluency of the print application process, both in screen printing and block printing, as the paste regularly needs to be reduced.
The invention of a natural indigo paste designed for various printing techniques presents a novel solution to long-standing issues in the use of natural dyes. With increasing awareness of environmental sustainability and the revival of traditional textile arts, a natural indigo paste designed for various printing techniques has significant cultural, environmental, and economic importance.
DESCRIPTION OF THE RELATED ART
Lohtander et al. presented that leucoindigo can be stabilized by nanocellulose suspensions for time periods allowing storage and application and that indigo is oxidized on the nanocellulose matrix leading to stable indigo blue water suspensions. Furthermore, they showed that the composite of nanocellulose and natural indigo has antioxidant properties, and that the purity of natural indigo from Isatis tinctoria in terms of indigo concentration is comparable to pure synthetic indigo. The also demonstrated a simplified green recipe for a paste of indigo and nanocellulose applicable for screen-printing patterns on cotton. (Journal of Cleaner Production 328 (2021) 129615)
Based on the potential outlined in the previous industry discussions, Rahmah and Hendrawan presented use of indigo paste dye, developed with screen printing techniques, to be applied to fashion products such as clothing. (e-Proceeding of Art & Design : Vol.7, No.2, August 2020, Page 3141)
Mongkholrattanasit et al. presented printing of woven cotton and knitted fabrics with natural indigo using a new thickening agent from the modified starch of wild taro corms. They applied printing paste to cotton fabric by using the screen printing technique. (Journal of Natural Fibers, DOI: 10.1080/15440478.2021.1875381)

Luo et al. presented the silicone non-aqueous/indigo dyeing system prepared with a small amount of aqueous solution, together with a small amount of alkaline agent and sodium hydrosulfite. They analyzed indigo dyeing performance and rubbing fastness of dyed cotton fiber in silicone non-aqueous dyeing system. They also presented influence of fixing agent on the rubbing fastness of dyed cotton fiber under different conditions. They presented mechanism between the fixing agent and dyed cotton fiber. Moreover, they presented scale-up test of indigo dyeing in the silicone non-aqueous dyeing system. (Journal of Cleaner Production 251 (2020) 119728)
Patent application no. JP2011162930A discloses method of screen printing by using a paste containing the indigo dye on natural fiber products, including a reducing agent and an alkaline auxiliary agent in the paste, and then printing by reduction and oxidation wherein hydrosulfite is used as the reducing agent, potassium carbonate is used as the oxidizing agent and the reduction treatment is carried out by steaming a natural textile product screen-printed with saturated steam and then oxidized and dyed in a liquid containing hydrogen peroxide.
Patent no. KR101222827B1 discloses a manufacturing method of a natural indigo texture printing paste comprising a step of uniformly mixing alginic acid and water for 24 hours at 60-100 °C, and obtaining a viscosity controller by removing the alginic acid by using a filter; a step of mixing the viscosity controller, caustic soda, sodium hydrosulfate (Na2S2O4) as a reducing agent, sodium formaldehyde sulfoxylate(CH3NaO3S) as a strong reducer, and indigo powder; and a step of mixing zinc chloride as a reducer into the mixture.
Nemeshwaree and Volle presented use of 100% natural Mayan-inspired blue indigo pigment, made from Sepiolite clay and indigo dye, in powdered and paste forms to perform pigment textile dyeing by pad cure process, and direct screen printing on textiles. They used a water-based bio-binder (40%) for both padding and printing. As reported, bio-based Na Alginate thickener allowed color fast printing on both polyester and cotton fabrics, while bio-based glycerin allowed good print color fastness on polyester only, yielding prints with excellent color fastness to wash (5/5), to dry and wet rubbing (5/5) and light (7/7). (doi: 10.20944/preprints202312.0517.v1)
While the literature provides valuable insights into the preparation and application of natural indigo paste, the presence of harsh chemicals may negate the sustainability benefits that natural indigo aims to provide, making it less appealing in the context of eco-friendly practices. Further, not a single document discloses an indigo paste and a method of its preparation that is suitable for block printing, screen printing and hand painting.
OBJECT OF THE INVENTION
Principal object of the present invention is to provide an indigo paste, a method of its preparation and a method of printing and hand painting using the said indigo paste that utilizes 100% natural constituents and reactants.
Another object of the present invention is to provide a natural indigo paste and a method of its preparation that is suitable for block printing, screen printing and hand painting.
Another object of the present invention is to provide a natural indigo paste and a method of its preparation that does not utilize any chemical reactants.
Another object of the present invention is to provide a natural indigo paste and a method of its preparation that is environmental friendly and with improved efficiency.
Another object of the present invention is to provide an indigo paste that is naturally reduced and that can sustain its reduced state for at least a month period without any further intermediate reduction requirements.
Another object of the present invention is to provide a natural indigo paste and a method of its preparation that is not harmful for the artisans working with it.
Another object of the present invention is to provide a natural indigo paste and a method of its preparation that do not required reduction of the natural indigo paste after its application in the form of print.
The existing indigo paste used in block printing does not use 100% natural reducing agents. So far 100% natural indigo has not been used in screen printing or hand painting. If chemical reducing agent is used then indigo paste cannot sustain its reduced state for longer period of time as the chemical reducing agent degrades very fast, generally in a time period of the order of few minutes and therefore use of the indigo paste with chemical reducing agent is not practical for the screen printing or hand painting process. If the indigo paste can retain its reduced state for longer period of time only then can it be practically used for block printing, screen printing as well hand painting process.
SUMMARY OF THE INVENTION
Present invention relates to a 100 % natural indigo paste comprising of mud paste, gum Arabic paste, calcium carbonate (lime), indigo pigment, natural fructose and water, and method of its preparation. The indigo paste and the method utilizing 100% natural reducing agent made it possible to use the natural indigo in screen printing, block printing and hand-painting and to achieve darker shades. Proportion of each constituent is discussed in detail description.
A method for preparation of a natural indigo paste for block printing, screen printing and hand painting comprising steps of (i) preparing a solution A of a mud paste, a gum Arabic paste and calcium carbonate, allowing it to ferment for minimum 10 days , (ii) preparing a solution B of an indigo pigment and a natural fructose, (iii) mixing the solutions A and B and boiling a mixture of solutions A and B at 60-70 oC for 15 minutes to obtain a paste and, (iv) allowing the paste so obtained to rest for 24 hours to obtain a natural indigo paste for use.
Use of 100% natural reducing agent retain the indigo paste used for printing in its reduced state for longer period of time which is of the order of one month making it possible to use it for a longer period of time. The natural indigo paste do not required reduction after application of print. Test results of the 100 % natural indigo paste are presented in the detail description.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings provides a clear understanding of the present invention along with a detailed description, and it constitute a part of this complete specification.
FIG. 1 illustrates a flow diagram depicting steps for preparation of a natural indigo paste for block printing, screen printing and hand painting and, method of its preparation.
DETAILED DESCRIPTION OF THE INVENTION
The preferred embodiment describes a natural indigo paste for block printing, screen printing and hand painting and, method of its preparation in detail with the help of FIG. 1.
Moreover, the detailed description of the present invention provides a clear understanding of the proportion and function of each individual constituent of the natural indigo paste composition.
100% natural indigo paste as per the present invention comprises of mud paste, gum Arabic paste, calcium carbonate (lime), indigo pigment, natural fructose and water.
The mud paste acts as natural thickening agent, natural binder and also natural pH regulator. The mud paste helps to achieve the desired viscosity of the natural indigo paste for its effective application in block printing, screen printing, and hand painting. The mud paste improves adhesion of the natural indigo pigment to the fabric fibres enhancing the durability and longevity of the color, contributing to better color fastness against washing and wear. Mud used in the mud paste is a natural and locally sourced material, aligns with sustainable practices. It reduces reliance on synthetic thickeners or binders, minimizing the environmental impact associated with chemical production and disposal. Incorporating mud from the particular geographical region in the mud paste used for preparing the natural indigo paste enhances the authenticity of the dyeing process and reflect cultural heritage. Mud is often an inexpensive and readily available resource, making it a cost-effective option for artisans and small-scale producers. This can lower the overall production costs of indigo dyeing while supporting local economies. The inclusion of mud in the natural indigo paste influences the texture and finish of the dyed fabric, potentially enhancing its aesthetic appeal. The mud paste in the natural indigo paste provide a medium that supports the incorporation of other natural ingredients of the said indigo paste allowing for the development of a broader range of colors and effects when combined with indigo. The mud paste helps in regulating the pH of the natural indigo paste, which is essential for the stability of natural indigo during the dyeing process. Maintaining an appropriate pH level can prevent premature oxidation and degradation of the natural indigo paste.
The gum Arabic paste in the formulation of 100% natural indigo paste serves as a natural thickening agent and a natural binding agent helping to achieve the desired viscosity of the natural indigo paste for block printing, screen printing, and hand painting and, enhancing the adhesion of the indigo pigment to the fabric fibers improving the durability of the color and reduces the likelihood of fading or washing out over time by enhancing the color fastness of the natural indigo pigment. The gum Arabic has excellent film-forming capabilities, which creates a protective layer on the fabric and helps to lock in the color and provides a barrier against environmental factors, contributing to the longevity of the indigo pigment. Being water soluble, gum Arabic allows for easy mixing and dispersion in water, facilitating the preparation of the indigo paste ensuring a smooth and homogenous paste, critical for uniform application. As a natural and non-toxic substance, gum Arabic aligns with the eco-friendly and sustainable practices that are increasingly important in the textile industry. The Gum Arabic contributes to the flexibility and workability of the paste, allowing artisans to manipulate the indigo pigment easily during application which is particularly beneficial in intricate designs and detailed patterns.
Calcium carbonate (lime) acts as a pH regulator, maintaining an optimal alkaline environment during the printing process which is crucial for the stability of the indigo pigment, preventing premature oxidation and ensuring consistent pigment uptake. Calcium carbonate is a natural, non-toxic substance that aligns with the eco-friendly focus of using natural indigo. Its use helps minimize environmental impact, ensures safety for artisans during the printing process and is economic.
The indigo pigment of the natural indigo paste provides the deep blue color characteristic of indigo printing. It is essential for achieving the vibrant and rich hues that are desired in various textile applications. Derived from the leaves of plants like Indigofera tinctoria, natural indigo pigment offers a sustainable alternative to synthetic dyes. Using a natural source aligns with environmentally friendly practices in the textile industry. Indigo has a long history in textile dyeing, especially in cultures around the world. Incorporating indigo pigment into paste formulations helps preserve traditional dyeing methods and cultural practices, reflecting the historical significance of indigo. Natural indigo pigment is biodegradable making it a preferable choice for sustainable and eco-conscious production processes. Indigo pigment exhibits excellent color fastness properties and can withstand washing and exposure to light without significant fading which is essential for textiles intended for everyday use. By combining with other natural materials and binders in the paste formulation it enhance the versatility of dyeing techniques, including block printing, screen printing, and hand painting. The use of indigo pigment allows for a range of color variations, from light to deep shades of blue, depending on the concentration and application methods used. This versatility provides artists and designers with creative flexibility. Indigo pigment has a unique chemical structure making it resistant to various environmental factors, such as UV light and moisture, which helps maintain the integrity of the dyed fabric over time.
The use of natural fructose in the formulation of 100% natural indigo paste act as a natural reducing agent, facilitating the conversion of indigo from its insoluble form to the soluble leucoindigo form during the printing process. This conversion is essential for the indigo pigment to adhere effectively to the fabric. Natural fructose stabilizes the leucoindigo form, prolongs its shelf life and ensures its effectiveness during printing. This stability is critical for maintaining the quality of the natural indigo pigment over time. Use of honey or date syrup as the natural fructose provides an eco-friendly alternative to synthetic reducing agents commonly used in dyeing processes. This aligns with the sustainable practices promoted in natural dyeing. Use of fructose enhances the overall color yield of the indigo printing process by promoting the reduction of indigo. Fructose is compatible with other natural ingredients in the indigo paste formulation allowing for the creation of more complex and effective dye formulations that can incorporate various natural additives. Natural fructose is biodegradable and non-toxic, making it safe for both the environment and users. Its inclusion supports the overall sustainability of the dyeing process. Fructose contributes to a softer feel of the dyed fabric. This can enhance the tactile qualities of textiles, making them more appealing to consumers.
The use of water in the formulation of 100% natural indigo paste acts as a solvent that dissolves the various components of the indigo paste, including the indigo pigment and other natural additives. This solubilization is crucial for creating a uniform and effective dye mixture. Water plays a vital role in the dyeing process itself, helping to carry the indigo pigment into the fabric fibers. The presence of water allows for better penetration of the indigo pigment into the material, ensuring even color distribution. Many natural ingredients used in the paste formulation, such as thickening agents and natural extracts, require hydration to activate their properties. Water helps in this activation, enhancing the performance of the natural indigo paste. The amount of water in the formulation can be adjusted to control the viscosity of the indigo paste. A suitable viscosity is essential for different dyeing techniques, such as block printing and screen printing. Water can help to regulate the temperature of the dyeing process to activate certain components. This control is essential for achieving the desired dye characteristics. Water is used to dilute other components, such as reducing agents or thickening agents, to achieve the desired concentration and performance characteristics. Water aids in mixing the various components of the paste, ensuring a homogenous product. It also makes the application of the paste easier, allowing artisans to work with the paste more effectively.
Following Table 1 shows proportion of each constituent in the natural indigo paste as per present invention.
Table 1
Constituent Weight percent
Mud paste 500 g (from Delhi pottery market)
gum arabic paste 300 g (Gujarat or Rajasthan)
Calcium carbonate (lime) 75 g (Gujarat)
Indigo pigment 20 g (Indigo Fast, Tamil Nadu)
natural fructose 60 g (Local Market)
Water 900 mL

Honey or date syrup is used as the natural fructose. Proportion of the Indigo pigment needs to be varied based on the intensity of colour needed. Water at a temperature of 40-50 oC is added in a quantity that is sufficient to maintain desired consistency of the natural indigo paste for its application.
A method for preparation of a natural indigo paste for block printing, screen printing and hand painting essentially comprises of the following three steps.
Step 1
In step 1, a mud paste is prepared, a gum Arabic paste is prepared and this prepared mud paste and the gum Arabic paste is mixed with calcium carbonate. The mud paste is prepared by mixing 500 g of mud with 500 ml of water at a room temperature. The gum Arabic paste is prepared by diluting 300 g of a gum Arabic in 300 ml water at a room temperature. The mud paste, the gum Arabic paste and 75 g of calcium carbonate are thoroughly mixed at a room temperature and allowed to ferment for minimum 10 days

Step 2
In step 2, a mixture of indigo pigment and a natural fructose is prepared. Mix 20 g indigo pigment and 60 g natural fructose in room temperature. With use of more quantity of the natural indigo pigment to attain a darker colour, the proportion of the natural fructose also changes. The ratio of the natural Indigo pigment to the natural fructose is maintained as 1:3 keeping all other ingredients same.
Step 3
In step 3, the solutions prepared under step 1 and step 2 are mixed. The obtained mixture is boiled it at 60-70 oC for 15 min. Paste obtained after boiling is allowed to rest for 24 hours. The natural indigo paste so obtained is ready for use and can be stored for future use.
In above method, honey or date syrup is used as the natural fructose. , Claims:We Claim:
1. A natural indigo paste for block printing, screen printing and hand painting characterized in that the natural indigo paste comprising:
• 500 g of a mud paste;
• 300 g of a gum arabic paste;
• 75 g of Calcium carbonate (lime);
• 20 g of Indigo pigment;
• 60 g of natural fructose; and
• 900 mL of water;
wherein
honey or date syrup is used as the natural fructose.
2. The natural indigo paste for block printing, screen printing and hand painting as claimed in claim 1, wherein proportion of the Indigo pigment varies based on the intensity of colour needed and, the indigo pigment and the natural fructose are mixed in a ratio of 1:3.
3. The natural indigo paste for block printing, screen printing and hand painting as claimed in claim 1, wherein water at a temperature in a range of 40-50 oC is added in a quantity sufficient to maintain desired consistency for application.
4. A method for preparation of a natural indigo paste for block printing, screen printing and hand painting comprising steps of:
• preparing a solution A of a mud paste, a gum Arabic paste and calcium carbonate;
• preparing a solution B of an indigo pigment and a natural fructose;
• mixing the solutions A and B and boiling a mixture of solutions A and B at 60-70 oC for 15 minutes to obtain a paste;
• allowing the paste so obtained to rest for 24 hours to obtain a natural indigo paste for use
wherein
• the mud paste is prepared by mixing 500 g of mud with 500 ml of water at a room temperature,
• the gum Arabic paste is prepared by diluting 300 g of gum Arabic with 300 ml of water at a room temperature and,
• the mud paste, the gum Arabic paste and 75 g of calcium carbonate are thoroughly mixed at a room temperature and allowed to ferment for minimum 10 days to prepare the solution A, and
• the indigo pigment and the natural fructose are mixed in a ratio of 1: 3 to prepare the solution B.
5. The method for preparation of a natural indigo paste for block printing, screen printing and hand painting as claimed in claim 4, wherein honey or date syrup is used as the natural fructose.