Reactive dyes have been used for dyeing cotton and other materials for a long time. Today, they are widely used in digital textile printing.
Digital textile printing is an inkjet-based printing method that enables printers to print high-quality designs on an extensive range of fabrics.
Reactive dyes are known for their bright colours, good colour fastness properties and ease of application. The majority of apparel and garment manufacturers use fabrics dyed with reactive dyes.
Reactive dyes are more environmentally friendly as all bonding chemicals are applied directly on fabrics during the pre-treatment process. Despite these good qualities, reactive dyes are more difficult to process.
After printing, fabrics should go through hot steam fixation and extensive washing processes. This means more time, more equipment involved in the process, higher production costs and hence a higher price for fabrics.
An extensive after-print washing process for reactive dyes means that dyes are bound in the fabric fibre and not lying on the surface.
Reactive dyes for cotton, viscose and silk
Cotton is a natural fibre that, especially within the fashion industry, is widely used for clothing because of its high moisture control, comfort and durability. With a digital textile printing machine, you can print on cotton.
To obtain the highest quality possible, most digital printers use reactive inks since this type of ink provides the highest wash fastness for prints on cotton.
Viscose is another natural fibre that is widely used in the fashion industry. As is the case with printing on cotton, you will get the best results when printing on viscose with reactive ink.
Silk is another natural fibre that is suitable for digital textile printing. Silk can be printed with reactive ink (when high-fastness is a priority) or with acid inks (if colour gamut is a priority).
The technology behind reactive digital printing
For digital fabric printing on cellulose material, we use reactive dyes. Printing with reactive dyes is more complicated in terms of the textile finishing process.
The digital printing process on fabric using reactive dyes consists of five stages:
- Printing
- Fixation (steam fixation)
- Washing
- Drying
- Softening (sanforising)
First, your design is printed on specially coated textiles of your choice.
In digital printing, the fabric first needs to be pre-treated, after which it will pass through the inkjet printer at high speed.
A digital textile printing machine uses a printable design of a digital data file, reads the right colour information and prints the colours onto the fabric.
Minuscule droplets of ink produced by numerous print heads colour the fabric. These print heads are positioned a few millimetres above the substrate.
When the printing is completed, reactive dyes are fixed on fabrics with steam, then washed and dried.
The final step in the process is when the fabrics are softened. This is also known as the sanforising process. The process is applied to some cotton bases such as viscose.
This process uses drums filled with hot steam and rollers under pressure.
The fabric goes through this process to pre-shrink it and compact its fibres, thus controlling any additional shrinkage.
Once this is done, the fabrics are ready to be delivered to you!
Digital fabric printing with pigment ink
Pigment dyes have been used for digital fabric printing for a number of years. One of the advantages of pigment dyes is that steam fixation and extensive washing processes can be avoided.
When using pigment dyes, the fabrics have to be pre-treated and they contain chemical bonding components. This makes them less environmentally friendly than reactive dyes.
In terms of colour brightness, fabric stiffness and colour fastness properties, pigment dyes are inferior compared to reactive dyes.
Printed fabric with pigment ink can be used for interior accessories, furniture elements, crafter needs, tradeshow graphics, flags, banners and others.
It is not recommended to use wet washing for fabrics dyed with pigment inks. The pigment dyes are lying on the surface of the fabric and not so much tied in the fibre of the fabric.
Conclusion
An increased number of companies benefit from the competitive advantage that it offers them – from the fast production rate and the possibility to print complex designs and fine patterns.
Fibre-reactive dyes are the most permanent of all dye types. This is because of their unique qualities.
Unlike other dyes, reactive dyes can form a covalent bond with the fabric. Fabrics printed with reactive dyes can be washed safely with white garments without the colour running into the whites.
The chemical bonds as explained above significantly improve the products’ colour, stability and washability. This is why the reactive dyeing of cotton is presently the most popular textile dyeing process in the world.
