INTRODUCTION OF DIGITAL PRINTING ON TEXTILE
Digital Printing on Textiles:
Introduction In the ever-evolving world of fashion, technology continues to redefine the boundaries of creativity and production. One of the most transformative innovations in recent years is digital printing on textiles.
Digital textile printing is a technique where colourful designs are printed on fabrics using digital ink-jet printing technology, by this any design can be easily and accurately printed on fabrics. Digital textile printing was started in the late 1980s as a possible replacement for analog screen printing. With the development of a dye-sublimation printer in the early 1990s, it became possible to print with low energy sublimation inks and high energy disperse direct inks directly onto textile media, as opposed to print dye-sublimation inks on a transfer paper and, in a separate process using a heat press, transfer it to the fabric.
Some Common Brands of Digital Textile Printing Machine
Chart 1- Digital printer Manufacturer
| Name of Machine Supplier | Origin of Country |
| Durst Alpha | Italy |
| Zimmer Machine | Germany |
| Atexco Machine | China |
| Reggiani | Italy |
| MS | Italy |
| Mimaki | Japan |
| Epson | Japan |
Different type of digital printing ink can be used on fabric based on type of Fibre
| Ink Characteristics of Digital Textile Printing | |||
| Ink | Fabric Type | Pre-treatment | Post-treatment |
| Pigment | Natural, Synthetic | No (Usually) | Dry heat |
| Acid | Wool, silk, Nylon | Yes | Steam heat |
| Reactive | Cotton, Rayon, Silk | Yes | Steam heat |
| Disperse Dye | Polyester | yes | Steam or dry heat |
| Disperse sublimation | Polyester | No | Dry heat transfer |
Chart 2- Ink vs Fibre
This cutting-edge technique offers designers unprecedented flexibility and precision, enabling the creation of intricate designs and vibrant colours that were once thought impossible. What is Digital Printing on Textiles? Digital textile printing is a method of printing patterns and designs directly onto fabric using specialized inkjet technology. Unlike traditional printing methods, which involve transferring designs from a medium onto fabric through physical contact, digital printing applies the ink directly to the textile. This process allows for greater detail, a wider range of colours, and the ability to produce short runs economically.
How It WorksDesign Creation:
Designers create patterns and designs using digital tools such as Adobe Photoshop or Illustrator. These designs are then converted into a format that the digital printer can interpret.
Pre-Treatment for Reactive Ink Digital Printing:
Reactive ink is commonly used for printing on natural fibers such as cotton, linen, and Viscose, Modal. The pre-treatment process for reactive ink is critical for achieving vibrant, long-lasting prints.
Here’s a detailed look at the steps involved:
Pretreatment:
The fabric is first cleaned to remove any impurities, oils, or dust that could affect the print quality. This cleaning process may involve Singing, Desizing, Bleaching, Mercerising, washing or using specific cleaning agents to ensure the fabric is free from contaminants. After this fabric need to be prepare for the digital printing application, This Pre-Treatment is very critical for Reactive digital printing.
Application of Pre-Treatment Solution:
A pre-treatment solution, also known as a pre-coat, is applied to the fabric. This solution typically contains several components:
Sodium Bicarbonate: Acts as an alkali to facilitate the reaction between the reactive dye and the fabric fibers.
Urea: Helps to retain moisture during the drying process, which is essential for the chemical reaction.
Thickeners: Ensure even application of the solution and improve ink adhesion.
Resist Salt: To ensure even distribution of ink without migration of ink.
The ratio of above chemicals depends on the type of fibre, GSM of fabric, Structure of fabric. As In this process alkali is applied first on fabric then ink is sprayed on fabric through nozzles of machine, hence pH of fabric before chemical application is very important.
The pre-treatment solution can be applied using various methods such as padding, spraying, or foam coating. Padding involves passing the fabric through a trough containing the solution, followed by squeezing through rollers to ensure an even coating.
Drying: Once the pre-treatment solution is applied, the fabric needs to be dried. Proper drying ensures that the pre-treatment components are evenly distributed and fixed to the fabric. This can be done through air drying, heat drying, or using specialized drying machines. The fabric must be completely dry before printing to prevent any smudging or bleeding of the inks.
Why Pre-Treatment is Important for Reactive Ink:
Enhanced Chemical Reaction:
The pre-treatment solution creates the right chemical environment for the reactive dyes to form covalent bonds with the fabric fibers. This ensures that the dyes are permanently fixed to the fabric, resulting in vibrant, wash-fast colours.
Improved Colour Yield: Proper pre-treatment ensures that the fabric can absorb the maximum amount of dye, leading to more intense and vibrant colours.
Fabric Compatibility: Different fabrics react differently to inks. Pre-treatment ensures that the fabric surface is adequately prepared to receive the ink, regardless of its type.
Printing: The fabric is fed through a digital printer, where specialized reactive inks are applied directly onto the textile. These inks penetrate the fibers and bond chemically with the fabric, resulting in durable and vibrant prints.
Post-Treatment: After printing, the fabric undergoes a post-treatment process, which may include steaming, washing, or heat-setting to fix the colours and ensure durability. Steaming is particularly important for reactive inks as it enhances the chemical reaction, ensuring that the dyes are fully bonded to the fibers.
In case of digital printing, it is most seen that stains are coming on fabric, as soon as fabric is coming out of ager. 90% technician works on the ager to stop such stains, though in my opinion it is not due to ager. It is due to pretreatment application method.
Here is the type of stain on fabric (Picture 1), we can see blackish blue line in below picture.
Picture 1- Stains on fabric after ager.
Picture 2 – Stain on printed fabric
Below are some precautions needed to avoid such stains.
- Pre-treatment Paste should contain anti migration chemical. Different company makes different chemicals, we can use of any supplier, but dosage should be minimum 3.5%, it can be used up to 4.5%, It is helpful if we are using stenter to apply chemical paste.
- If we use Rotary machine to apply pre-treatment paste the anti-migration chemical is not needed, here we should use two screens to apply paste on fabric and there should be gap in between screen so that chemical goes inside the fabric. But it is not reaching on the back side of fabric.
- Fabric should not be dried in any condition more than 110 deg C,
- Fabric should not be allowed to absorb moisture from the atmosphere, hence pack properly with polythene.
- Fabric on digital printing machine also should be dried properly, here fabric temperature should be not less than 105 deg c and not more than 115 deg C. It is very important that fabric has been completely dried, the temperature mentioned is on fabric, not chamber. based on length of drying chamber we can keep chamber Temperature 10 to 15 deg c more than fabric temperature.
- Fabric should be covered properly until it is passed through ager.
- During ager it must be ensure that fabric is not touching each other on the printed side.
- If we are getting stains after ager, we can supply dry air also of heated up to 105 deg C along with steam. The purpose of this step to keep fabric just warm dry, not to getting moist during ager. Though steam will make fabric little damp. In this case shade may become lighter also, hence sample and bulk condition must be exactly same from pretreatment chemical padding to ager.
This is followed by thorough washing to remove any unfixed dye and pre-treatment chemicals. In general washing fastness of Digital printed fabric being very good, hence we need to give wash at 90 deg c for 15 to 20 min. with detergent having anti staining property. In washing the most critical part is first wetting squeezing, as it is the area where all paste will be removed from fabric. after this we can keep water ph around 5, and wash with detergent.
Benefits of Digital Textile Printing
1. Unmatched Flexibility and Customization Digital printing allows for an almost infinite variety of designs and colours, enabling designers to experiment with new ideas and create customized pieces. Small production runs are also feasible, making it ideal for bespoke orders and limited-edition collections.
2. High Resolution and Detail Digital printers can produce high-resolution prints with fine details that traditional methods struggle to achieve. This is particularly beneficial for intricate patterns and photographic images.
3. Eco-Friendly Digital printing uses less water and energy compared to traditional methods. Additionally, the ability to print on demand reduces waste from overproduction.
4. Speed and Efficiency The digital process is faster from design to production, reducing lead times and enabling designers to respond quickly to market trends.
Applications in the Fashion Industry Digital textile printing is revolutionizing various sectors within the fashion industry:
Fast Fashion: Brands can quickly produce and bring new designs to market, staying ahead of trends.
High Fashion: Designers can experiment with bold, complex designs without the constraints of traditional methods.
Home Textiles: Customizable home décor items like curtains, cushions, and upholstery benefit from the flexibility of digital printing.
Sportswear: Digital printing allows for vibrant, durable designs on performance fabrics.
Challenges and Considerations:
While digital textile printing offers many advantages, it also presents challenges. The initial investment in high-quality digital printers and inks can be significant. Additionally, achieving consistent results requires meticulous calibration and maintenance of equipment. Designers and manufacturers must also consider the limitations of fabric types and the suitability of digital inks for different materials. The Future of Digital Textile Printing The future of digital textile printing looks bright, with ongoing advancements in technology promising even greater capabilities. Innovations such as 3D printing on textiles and the development of new, sustainable inks are set to further transform the industry. As digital printing becomes more accessible, we can expect to see even more creativity and innovation in fashion and textile design.
FLOW CHART FOR THE PROCESS SEQUENCE:
Below is the typical process flow for the knitted cellulosic fabric for reactive digital printing
Conclusion:
Digital printing on textiles is not just a technological advancement; it’s a paradigm shift in how we think about design, production, and sustainability in the fashion industry. As this technology continues to evolve, it will undoubtedly open new possibilities for designers and consumers alike, making fashion more vibrant, personalized, and eco-friendly. Here defined precautions are based on my experience on digital printing, before applying these things in bulk small scale trial is always recommended, as each digital printer has different size of dryer, ant most of them are not of suitable length.
