Custom Printing: Digital Printing on Woolen Fabric

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On a daily basis I get a Google Aggregator list of articles about both digital printing and offset printing. I find these extremely useful on two counts. First, even if I just read the headlines, I can immediately see what’s trending in commercial printing. I know what to research. Second, I can click through and research in depth any subjects that interest me.

So I’d encourage you to set up a similar feed of articles if you are a student of custom printing, as I am.

Over the last several months, I have noticed an uptick in the number of articles about digital printing on fabric. This includes both direct-to-garment (DTG) work and printing on rolls of fabric. In the case of DTG, fully formed pieces of clothing are stretched over a platen in the printing equipment, and some form of inkjet printhead array decorates a portion of the clothing. In the latter, images are printed on rolls of fabric, which are then measured, cut, and sewn into complete pieces of clothing.

The two imaging techniques I have found are direct inkjet, which works for cotton fabrics, and dye sublimation, which works for polyester fabrics. The goal is to get the coloration deep into the material, where it can bind to the fibers of the fabric.

Direct inkjet technology sprays droplets of color into the cotton. In contrast, dye sublimation starts with the direct digital printing of the image onto transfer paper using dyes. Then, in a separate step, with the transfer sheet flat against the fabric, applied intense heat causes the printed image from the transfer sheet to migrate into the mesh of polyester fibers and bind to them (it goes from a solid to a gas, skipping the liquid state, and then solidifies again in the fabric). This is a very strong bond. In fact, it is my understanding that dye sub on polyester is even more durable than inkjet on cotton. And, there have been forays into direct dye sublimation of images onto polyester (skipping the transfer sheet but retaining the high heat), although the challenge is to keep the fabric completely flat during the transfer process.

So these are the options, using different coloration technologies for different substrates (cotton and polyester).

But What About Wool?

Yes, exactly. What about wool? We have made clothing out of wool for centuries. Now, finally, I’m beginning to read Google Aggregator articles on the custom printing of woolen fabrics. How exciting.

First, a little backstory. For most of history, the preferred way to decorate wool has been to dye it, in bulk. (Imagine vats of liquid dye.) This consumes a huge amount of water. Much of the coloration runs out of the fibers during the washing process. And there is no way to get photographic-quality image detail and resolution, which even now you can find on polyester and cotton bathing suits at the beach. But this is changing.

First, here are the benefits of wool:

1. 1. Wool is warm.

1. 1. Wool absorbs moisture.

1. 1. Wool is flame retardant.

1. 1. Wool has good drapability (ability to conform to whatever it is draped on, like the human body).

1. Wool is resilient (returns to its original form).

Here are the challenges with decorating wool:

1. 1. The coloration has to get deep into the fibers, quickly and easily.

1. The color has to stay there.

Recent strides in commercial printing technology have improved the surface characteristics of woolen fabric in such a way as to improve its color receptivity to fabric dyes, the pigment depth (ability to get coloration deep into the fibers), and the color fixation and color fastness (keeping the dyes attached to the woolen fibers). This has been done with chemical pretreatment and/or additions to the ink paste mixture (including, for instance, some of the following: monoethanol amine, benzyl alcohol, urea, and ammonium persulphate). Some of this processing actually strengthens the wool as well.

(If all of this technical information interests you, you might want to research Redox System; Dr. Suman Pant’s “Techniques to Improve Printing Performance of Wool Fabric,” 09/2010; and Think Positive, experts in the UK on direct-to-fabric custom printing.)

Here’s how it’s done (based on my recent reading about Think Positive). This includes printing on woven wool and knits, wool blends such as wool denim, wool velvet, lightweight wool twill, and wool fur.

(Keep in mind that wool is now considered a “luxury” fabric, particularly when compared to cotton and polyester. For instance, such famous brands as Vivienne Westwood benefit from this technology.)

The Process

In my reading, the custom printing was done directly onto rolls of fabric, as opposed to printing onto fully formed garments:

1. 1. Printers first pretreat the wool with a blend of seaweed thickener, urea, salt, and lemon juice (citric acid).

1. 1. The printers then use a water-soluble textile dye.

1. 1. The process sprays the dye through an array of inkjet print heads. (In the case of Think Positive, the digital press incorporates an 8-color inkset from which more than a billion colors can be mixed.)

1. 1. The fabric is held in place during imaging by a “sticky belt.”

1. 1. The printed fabric (with the dye sitting on top of the wool) is passed over a heat tray, which dries the dyes to the touch.

1. 1. Steaming the fabric opens the fibers and allows deep ink penetration into (and bonding with) the wool fibers. This sets the coloration (and images) and makes it permanent and durable.

1. 1. The printer washes out the precoating solution.

1. There has even been experimentation into custom printing both sides of the fabric.

The Benefits

Here are some thoughts culled from the articles I read:

1. 1. Wool is a high-end fabric. Printing on wool opens up areas of high fashion once accessible to only cotton and polyester fabrics.

1. 1. Dyeing wool used to be a long, complex, arduous process, which consumed copious amounts of water. (Also, some wool dyeing was done not at the fabric stage but at the yarn stage, dyeing skeins of wool.) Now, using digital commercial printing technology, it’s possible to print ready-to-wear items much faster.

1. 1. This lends itself to printing short production runs and even prototypes.

1. 1. Due to the quick make-ready, the digital process eliminates the need for large runs. Therefore, there’s no need to store inventory (which might go out of fashion). Also, presumably, it’s possible to personalize individual items.

1. 1. Design flexibility has gone through the roof. Think about the detail and photographic resolution of digital printing vs. dyeing fabric.

1. 1. The process is sustainable and environmentally friendly. It uses far less water than prior technologies.

1. The dye itself is environmentally friendly. In addition, excess dye can be recycled.

The Takeaway: How Can You Benefit as a Designer or Printer?

If you’re a designer or printer, how can you benefit from this new technology? First of all, fabric printing in general opens up two hot industries for you: apparel and interior design. The ability to print close to photographic quality designs on wool puts your design and commercial printing skills and knowledge in high demand.

If you’re a printer, it seems to me that buying the equipment required to produce and sell fabric printing would be less of a hurdle than adding traditional fabric dyeing technology (vats of colored dye) with its high water usage and need for storage of large printing runs.

So, as with any new commercial printing technology, my advice is to first read everything you can find on the subject of fabric printing for apparel and interior design (wall coverings, bedspreads, etc.) to see how you might apply your current level of expertise and what more you need to learn.

This is just the start. It’s really quite exciting, don’t you think?

This entry was posted on Wednesday, September 15th, 2021 at 8:29 pm and is filed under Fabric Printing. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.