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What Is Reactive Printing? An In-depth Guide Covering Everything You Need

Modern society is absolutely no stranger to printed fabrics. Do you know how complicated patterns are printed on fabrics? And why do some printed patterns sit on the fabrics permanently? Why do some seem to jump off but others do not?  If you are around the block,  reactive printing may hit upon you right away.  But any detailed information? The following guide is curated to shed light on the intricacies of reactive printing.

What Is Reactive Printing on Fabric?

Reactive printing, or more precisely reactive dye printing is an advanced technique of printing using reactive dyes. This type of dye can form a covalent bond with the substrate, typically cellulose and protein, through a series of heat-activated reactions. The covalent bond is concisely, a steady and firm chemical bond, making the dye a part of the substrate. 

Consequently, reactive dye printing is an effective and frequently used craft to transfer designs and patterns onto fabrics. It can collaborate with digital printing machines to produce intricate patterns in vibrant colors effectively. In the textile industry, it mainly applies to natural fabrics and regenerated fabrics with natural fibers as their raw materials. You can leaf through its applications in the following list.

What Is Reactive Printing on Fabric

Fiber Reactive Dyes

Reactive printing gets its name for the unique type of dyes it uses. Furthermore, fiber reactive dyes can not work well by themselves, but with special additives and auxiliaries.

What Is A Reactive Dye?

A reactive dye is a type of dye that diffuses in water and establishes a steady chemical bond with fibers at a molecular level. It is revered for its incomparable fastness properties – it can be permanently attached to a substrate. The fiber reactive dye has versatile applications in textile printing, including direct printing, discharge printing, resist printing, inkjet printing, etc. For another, the reactive dye also hydrolyzes. It undergoes stronger hydrolysis in lower dye concentrations, higher pH value and higher temperature. 

Additives and Auxiliaries to Reactive Dyes

In reactive dye printing, other chemicals except dyes are necessary for the reactions. Fibers need to be coated with solutions dissolving them before printing (usually in the pretreatment). Here is a brief list of these chemicals.

  • Salt (mainly sodium chloride and sulfate): It promotes the dye uptake.
  • Alkali (sodium carbonate, bicarbonate and caustic soda): It promotes the fixation of colors.
  • Urea: It may be added to the padding liquor in continuous processes
  • Sodium silicate: It is used in CPB (the cold pad-batch method), or in padding mangles.

How Fabric Is Printed by Reactive Printing?

Reactive printing is a multi-step process. Let me take reactive printing with digital printing machines as an example.

Pretreatment

This process is fundamental to the optimal printing effects in printing.  A staple of pretreatment is to soak the fibers into a formulated chemical bath, including additives and auxiliaries to dyes (someone regards it as sizing). Without this bath, fibers can not take in dyes well and assume pellucid patterns. One of the reason lies in that raw fabrics tend to disperse dye solutions with their narrow tubes automatically, physically called capillarity. So, it is this chemical bath that locks these narrow tubes. It reduces the dye bleeding which decreases the clarity and precision of printed patterns.

Besides, the chemical bath removes curling and wrinkling of fabrics and they become stiffer – easier to pass through printing machines. Then they are dried on stenters and rerolled to be ready for printing.

Printing

Pretreated fabrics pass through digital inkjet printers of reactive dyes. It is the time when fibers absorb dyes and dyes diffuse and penetrate the surface of fabrics. You can get fabrics with printed patterns when this operation is done, however, they are not permanent or long-lasting.

Steaming/Curing

It is a process of color fixing. That is, the high heat sparks the chemical reactions of reactive dyes and fibers, with the help of salt and alkaline in the pretreatment bath. The temperature of steaming varies from 215℉ to 356℉ (for the properties of different fabrics). The steaming time also differs but is always less than 25 minutes. Coming out from the steaming chamber, dyes have settled down on the fabrics.

Washing and Drying

During washing, the fabrics go through 2 processes, rinsing and soaping. The rinsing is to wash them in cold waters for at least 3 times. It aims at removing the residue of alkaline agents.  On the other hand, soaping gets rid of the excess dyes not integrating into fibers. The soap used should have strong abilities to disperse and emulsify in water,  and clean free chemicals. Moreover, it should be under the temperature of 195 ℉ and in a neutral environment.

Fabrics get dried in the oven or stretch dryer (also called the setting machine). The temperature should be meticulously calculated as too much heat may yellow the fabrics.

The above contains the basic processes of reactive printing. In addition, the fabrics may require finishing treatment to promote touch and texture.

Advantages and Disadvantages of Reactive Printing

Advantages of Reactive Printing

  • Its products assume high fastness, including color fastness, light fastness, wash fastness and rub fastness.  Among these properties, they perform excellently well in wash fastness and color fastness – they can be washed over and over with negligible fading.
  • Its products are of superior durability and only need easy maintenance (also a result of their fastness properties).
  • Reactive printing is preferred for its wide spectrum of hues. Furthermore, you do not need to compromise on poor color reproduction for its brilliant colors.
  • It has economical crafts and easy conductions. It is cheaper than Vat dye printing.
  • It is more sustainable than some types of textile printing such as sulfur dye printing, ice dye printing and Vat dye printing.

Disadvantages of Reactive Printing

The utilization of dyes in reactive dye printing is relatively low, generally 60% to 70% (other dyes hydrolyze or just do not react with fibers). That being so, it produces a large amount of colored sewage. Further, the sewage involves different types of salt and alkaline in need of special treatment. One of the additives, sodium chloride, is especially hard to treat. 

As one method fixing dyes by reactions, one solid color may turn out to be slightly different in 2 lots (finished products that do not print together). There are so many variable features that it is challenging to pursue a completely consistent color.

Reactive Printing VS Other Printing Methods

What Is the Difference Between Reactive and Pigment Printing?

Pigment printing does not fuse pigments (It does not use dyes) into fabrics, but glues them on the surface. It is mostly applied in direct printing.

Compared to reactive printing, pigment printing is more economical and of faster production. However, it coats fibers with some flammable solvent and vibrant pigments – less safe, harder hand feel and a pungent smell. Per contra, pigment printing has wider applications. For example, poly-based fibers are often printed by pigments and reactive printing does not work on them well. In addition, reactive printing can print on both sides of fabrics while pigment printing ONLY works on one side. 

What Is the Difference Between Sublimation and Reactive Printing?

Sublimation printing transfers the patterns onto fabrics indirectly. It at first prints the patterns onto a transfer paper and then it is heated and pressured to fix the patterns onto fabrics. As a newborn method of printing, sublimation printing debuted in the textile industry owing to the slathering of polyesters. It is more or less an exclusive way to print on polys. 

Sublimation printing settles inks by a heat press while reactive printing by reactions initiated by steaming heat. They both produce vibrant and faster colors, but sublimation printing has a narrower application and costs less.

How to Print Silk by Reactive Printing?

Silk, as one of the finest natural fabrics, can be printed by fiber reactive dyes. I happen to know this printing process well. Here are the key points of printing silk by reactive dyes. You may get inspired by this epitome. 

In the factory, silk to be printed and the desired effect picture should take meticulous examinations and calculations first. These works are essential and inevitable in every printing because varying types of silk need different formulas for treatment. Then silk takes a unique chemical bath for pretreatment. Professionally, both the composition and the concentration have minute differences every time. Next, silk fabric coated with chemical solution passes through idler wheels to eliminate excess liquid. Then the silk enters the drying areas. After that, silk fabrics officially step into printing machines.

What is connected with the printing chamber is the steaming chamber. Unlike regenerated fabrics, silk can not withstand extremely high temperatures, so the steaming temperature should be able to promote the combination of dye and fibers but within silk’s tolerance. Normally,  silk is steamed at a temperature between 215℉ to 221℉. It is better to control the steaming chamber under this temperature than just the steaming boxes. The operation time is about 10 to 15 minutes. Sometimes, silk fabrics may get through a hot-air dryer of 248℉ and then get ventilated and recover some moisture before steaming. 

The steamed fabrics afterward get soaped in the open-width soaping machine.  First, spray them with cold water twice, and then lukewarm water of 122℉ and 158℉ take turns. Second, wash them with special silk soapy solutions between 176 ℉ and 196 ℉. Third, rinse fabrics with cold water. Fourthly, neutralize the alkaline with acetic acid. Eventually, rinse them again. In the next, silk accesses the drying chamber. 

After washing and drying,  silk fabrics should take close inspections for the precision and reproduction of designs and patterns. Do you think the printing is over now? Absolutely no. The sewage newly generated should be gathered and poured into a central processing chamber – They can be reusable water and employed in printing again and again. As you may know, a responsible factory of textile printing should be equipped with pollution treatment and water recycling systems for printing was once notorious as a dirty industry. For more details, you can visit Sinosilk’s factories in person or watch our videos. 

FAQs

What Is Capillary Action?

Capillary action is one of the reasons for the necessity of pretreatment in fabric printing. In the natural world, water solutions climb up tiny tubes without any external force and even in opposition to gravity. Jurin’s law in fabrics contributes to the diffusion of dyes and thus printed patterns may get blurred and cross-colored.

How to Tie Dye with Fiber Reactive Dyes?

You should prepare urea and soda ash to tie dye with fiber reactive dyes. Apart from normal procedures of tie-dyeing, you should deal with fabrics and dyes with these 2 substances between prewashing and applying dyes. Soak your tied fabrics in soda ash for about 5 minutes. Then mix the urea with dyes. You should pursue a tested formula, and measure the right amount of urea. Dissolve the dosage into lukewarm water and mix the solution up with dyes into a flowing paste. After that, follow the steps of tie dyeing.

What Is Eco Printing? What Is Eco Solvent Printing?

Eco printing is a sustainable and eco-friendly method of printing on fabrics by natural dyes. Eco solvent printing, on the other hand, is an eco-friendly way to print on paper.

Conclusion

Reactive printing provides a wide array of colors and produces enduring and vibrant effects. If you need custom services of printing on natural fabrics, Sinosilk is your credible workmate. We above all offer top fabrics, including various types of silk fabric, silk blends, etc. We also render printing services of on-top machines and expertise teams. Within the industry, Sinosilk’s custom printed fabrics are publicly praised for high color reproduction, sleek and precious lines, and quality two-sided printing. We can also do quality printing on fabrics hard to print, such as wool and silk cashmere. If you want professional help, come and contact us.

More Resources

Reactive dye – Source: Wikipedia

Reactive dye printing – Source: Wikipedia

What is screen printing?Source: Sinosilk

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