Digital printing for denim? Oh good? Yes, report NCSU researchers

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RALEIGH- Drop by drop, researchers at North Carolina State University printed ink on cotton fabric to create a “digital” denim fabric resembling six different styles of jeans. When they asked a team of textile experts, they found that, overall, samples made with the computer and printer matched, on average, well with denim made using traditional methods in more labor intensive.

However, in the Journal of Imaging, Science and Technology, the researchers reported that certain styles of jeans were easier to reproduce with inkjet printing than others, and that certain characteristics, such as color, were more easily reproduced. After further study, the researchers said they expect digital printing to be a viable method for making new denim products in the future, with less waste.

The abstract spoke to study co-author Lisa Chapman, an associate professor of textile and apparel technology and management at NC State, and lead author Ming Wang, a former NC graduate student. State, about the study.

The abstract: Why were you interested in digital jeans printing?

Chapman: Denim is a must in our wardrobe. Almost everyone has several pairs of jeans in their closet. This is a very popular item. It is also one of those clothes that are sold all over the world. But the denim-making process is water-intensive. In particular, the industry is considering the following question: how to reduce the amount of water used for denim?

Wang: To make jeans, the cotton thread is dyed, then there are finishing and washing processes that give the jeans a certain look. These processes can have many negative environmental impacts such as water pollution and energy consumption. I wanted to explore another way to produce the same look of denim that is more environmentally friendly.

AT: What is inkjet printing? Why is it used in textile manufacturing?

Chapman: Inkjet printing is really similar to your home inkjet printer in that it will shoot droplets of ink onto the fabric. But in this case, it drops textile dye on the surface of the fabric.

We consider it to be an emerging technology insofar as its market share is still quite low in textiles. But it has potential mainly because it uses less water, it uses less energy, and it’s a print-on-demand process. So you eliminate some of the steps in the coloring process and have unlimited colors. To print using the traditional process, the more you increase the number of colors, the more you increase the cost of the design. Inkjet printing is not like that; 200 colors equals two colors in cost.

At some point in the history of apparel and home furnishings, we had a lot of the same products. We were printing a lot of yards of the same design. Now we’ve moved into a consumer group that demands a lot of variety. When you have a lot of variety, you have more impressions and you have smaller production runs and screen costs can be very high. Inkjet printing becomes more cost effective.

AT: In your experience, how did you create digital denim?

Wang: I used a high resolution scanner to scan a very high resolution image of the jean swatches, then transferred it to a computer file that could contain the color and transparency information. Next, I chose a pre-treated fabric that has the same weight and texture as the traditional jeans samples. In the digital printing lab, I had access to four different inkjet printers. After struggling to find the right ink and the right printer, I chose the latex printer, which is more respectful of the environment. I chose six different types of denim that have different washing effects. We have discovered that digital printing can replicate all of these effects.

AT: What does the expert panel say about the quality of digital denim?

Wang: We found 12 experts from the textile industry who have a lot of experience, especially on denim and color matching. We asked them to compare digital denim and traditional jeans samples. For color, traditional and digital denim were very close. On a scale of one to five, with one being the greatest difference, five meaning no difference, the average score for color was around three or above three. Which means we had a good match for the color.

Besides color, we also evaluated line quality, texture, lightness, and overall match. What we’ve found is that it’s very difficult to get the quality and texture of the line. We think the reason could be that traditional dye has high ink penetration. But for digital printing, it’s printing on the surface of the fabric, and it doesn’t penetrate the fabric that much. This might cause the line quality and texture difference.

AT: What is the future of digital denim?

Wang: If anyone could solve the ink penetration problem, I believe we could mass produce denim products with high speed printer. This could lower the cost of production. However, since mass production is not quite realistic yet, we could use digital printing for high-end denim products like home textiles or garments. For kids, they are getting bigger every day, so you might have something that looks like jeans.

Chapman: It can be difficult to replace traditional denim, but there are other markets where it could do a much better job. Jeggings is a great example. In addition to baby clothes, there are situations where you want the denim look, but want higher drape and a softer fabric, such as dress shirts or women’s dresses.

AT: What is the future of digital textile printing?

Chapman: Although there is quite a steep learning curve for digital printing, there are also benefits with reduced energy consumption, chemicals and water waste when we compare digital printing in serigraphy. The dot-com market will also boost digital printing. We will look at new technologies that speed up the production cycle to get goods to consumers faster.

(C)NCSU

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