The choice of black ink matters a lot in digital textile printing. Black is most often the “key” color in the CMYK color process, alongside cyan, magenta and yellow. It not only adds depth and contrast, but is the basic component in every color, colorway and design.
Many printers will choose a Neutral Black for the sake of flexibility. But, depending on the application, this may not deliver the best end result or avoid production issues that could impact productivity, according to Mattia Perri, Global Technical Manager, Inkjet Application. He offers three reasons to look beyond Neutral Black.
1. To avoid the “Wimbledon effect”
The Wimbledon or football field effect refers to a slight color difference between alternating sections of a shaded black design – akin to the stripes you see on a grass tennis court or football pitch that are achieved when the grass is mown and rolled in alternate directions.
In digital textile printing, one pass is printed from left to right, whereas the next is printed from right to left. Since the CMYK printheads are positioned next to one another in the printhead carriage, this directionality makes a difference. When printing a shaded black with Black and Red ink, for example, the Black ink drops will reach the fabric a little earlier than the Red ink drops in the left-to-right pass and a little later in the right-to-left pass. This is enough to cause a discernable difference in the final black color.
Uni-directional printing is possible, as is increasing the number of passes, but both of these approaches will significantly slow down production and impact productivity.
“Whenever you mix a Neutral Black ink with other colors to reach the desired shade, you are at risk of the “Wimbledon effect” when printing bidirectionally or with a limited number of passes. By choosing a shaded black that fits your requirements and can be used as a stand-alone color, printing speed and quality will not be compromised,” Perri advises.
2. To avoid the dithering effect
“Dithering is a fundamental skill of the digital printer. When you don’t have enough channels for light Cyan, light Magenta or Grey, dithering lets you vary color density to create those light shades anyway,” Perri explains. “For example, you can trick the eye into seeing grey tones through a random arrangement of Black ink drops with varying spacing.”
The dithering effect, on the other hand, is when individual printed dots are visible in the design, creating a grainy pixelated-looking image.
“When printing shades of grey, the dithering effect is most likely to occur when printers choose the darker, more concentrated Neutral Black inks. To achieve a quality print of varying color depth, the answer is to have a mid-tone Black on hand or to invest in a separate Grey ink,” Perri says.
3. To achieve consistency between batches
A shaded black ink allows mills to consistently and accurately achieve the right tones without depending on software shading. When compared to a standard Neutral Black inks, a shaded black thus enhances consistency between batches during steaming without compromising speed or quality.
Another consideration is the ink chemistry. Vinylsulfon (VS) black inks are good when you need intense colors or neutral shades with light or dark tones. However, these inks do require an optimized printing and steaming process to minimize the risk of reduction. In contrast, monochlorotriazine (MCT) black inks offer a good balance of color and fixation conditions, with excellent stability to reduction, especially during steaming.
“MCT inks also allow fabrics to be stored longer between printing and steaming without any risk of hydrolysis, enhancing reproducibility and process efficiency,” Perri says.
The choice of black ink supplier is also crucial. When selecting between different brands, printers should consider coloristic performance, fastness performance and reproducibility, as well as print reliability and overall coloristic cost control.
Black inks for a range of printing needs
Ensuring that textile printers can select the exact shade for their application without compromising performance or production efficiency, Huntsman Textile Effects offers six different types of high-performance black inks.
- NOVACRON® DEEP BLACK XKS-2001, which is recommended for mid-tones and relatively light shades without dithering;
- NOVACRON® STRONG BLACK XKS HL, for cool bluish dark tones with slightly higher light-fastness properties;
- NOVACRON® BLACK XKS HD 9000, which delivers a deep black color with a balanced bluish shade; and
- NOVACRON® ADVANCE BLACK 12000, a warm reddish MCT black ink for very dark tones.
The range also includes two Neutral Black inks, which are ideal for printing black shades and creating darker basic colors for fashion and sportswear designs on a range of cellulosic fibers:
- NOVACRON® ADVANCE BLACK-10000, Textile Effects’ most neutral MCT black ink for very dark tones without any performance compromise; and
- NOVACRON® JET BLACK XKS HDA, a stand-alone neutral VS black ink for dark tones, which is particularly suited to printing on viscose.
Mattia Perri, Global Technical Manager, Inkjet Application, Huntsman Textile Effects
Sergio Vito Prenna, Global Marketing Manager – Textile Printing, Huntsman Textile Effects
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