My fiancee brought home new printed sheets last week, and I was truly impressed with the strides that have been made in digital large format printing on fabrics. The sheets were covered with handwritten letters and images of envelopes spread across the large, queen-size format. Handwritten text in some areas included drop shadows in gray type, and there were stamps printed in orange and black.
I want to contrast this bedsheet with two drapes for which my fiancee had paid significantly more money a number of years ago. As beautiful as these drapes are, covered in large gray handwriting, the artwork is much simpler than the art on the sheets. The cursive strokes of the handwriting are all one color. They are beautiful, but simple.
Based on my research, this is how I think the two vendors printed the fabric art. I think the drapes were produced by a screen printing company in a light gray type on sheer white curtains, and I think the sheets were produced by the newer technology of direct to fabric printing, which includes both inkjet-based large format printing and dye sublimation direct to fabric printing. Both of these large format technologies are relatively new.
Moreover, given the difficult news about magazine printing and newspaper printing, I’m always glad to see growth in the commercial printing field. In addition, my fiancee’s insight into the pricing for these bedsheets reflected the consumer demand for this technology. Specifically, she had seen the sheets online at a local bed and bath store. Unfortunately, they were out of stock in all store outlets. However, they were listed on eBay for significantly more than the bed and bath store had charged. That’s consumer demand.
The Technology Options
I did some research into the technology involved.
Apparently large format inkjet printing works best for cotton fabric, whereas dye sublimation works best for polyester. More specifically, inkjet commercial printing becomes duller on fabric as the amount of synthetic material increases.
With both inkjet and dye sublimation, the wet ink is cured using heat and pressure on additional equipment (a heat press or conveyor dryer).
In inkjet printing, the water based dye or pigment ink is sprayed onto the fabric. In dye sublimation fabric printing, dye is turned directly from a solid into a gas without first becoming liquid. It becomes infused into the fibers of the fabric as it turns back from a gas into a solid and bonds with the polymers of the synthetic material.
Some dye sub printers produce the image on an intermediate transfer sheet. They spray the dye (in a liquid carrier solution) onto the transfer paper, and heat and pressure sublimate the dye (turn the solid ink on the paper into a gas) and transfer the dye to the fabric. The carrier solution stays on the transfer paper.
In dye sublimation printing, heat also makes the colors more vibrant because the dyes are specifically designed to bond only with polymers. Images on the transfer sheets tend to look dull until heated and transferred to the fabric. In fact, the greater the synthetic (i.e., polyester) content of the fabric, the more brilliant the colors appear.
I have also read about a dye sublimation process used by Velotex that sprays the dye directly onto the fabric using a large format inkjet printer. The fabric then travels through a separate heating and roller assembly that sublimates the dye and infuses it into the fibers of the fabric. This eliminates the transfer sheet and allows for continuous, unattended operation of the dye sublimation equipment.
Another benefit of dye sublimation digital large format printing is that the resulting printed fabric is very soft (has a smooth “hand,” in industry parlance). Since the finished product is softer, it retains the draping qualities of the fabric.
Alternate Technologies
Another resource that I found describes an inkjet process for non-synthetics using textile dyes or pigments. A pre-treating step is added in which steam-set inks are used, or a washing process follows the printing step using mordants (substances that facilitate the dyes’ or pigments’ bonding with the base fabric).
So there’s more than one way to achieve digital large format printing success.
What About the Sheets My Fiancee Bought
This is what I think, although I’m not certain. First of all, the bed sheet is very large, so I would assume that either the job had been inkjet printed using fabric dyes or printed via dye sublimation using direct to fabric technology without a transfer sheet. Moreover, the bedsheet includes three panels sewn together into one large sheet. This would support my theory that a large format (perhaps a 64-inch) inkjet printer had been used.
Which of the two processes the manufacturer chose (inkjet or dye sublimation) would then depend on the fabric composition. I looked at the tag attached to the sheets and noted that they are 100 percent cotton. Therefore, I would assume that dyes or inks had been printed directly onto the fabric using an inkjet printer and then the sheets had been treated with heat and pressure to cure the dyes or inks.
My fiancee mentioned that her online research revealed that some people who had bought the sheets complained of a strong smell. Wikipedia includes the following as mordants used to facilitate the bonding of dyes to fabric: “…tannic acid, alum, urine, chrome alum, sodium chloride, and certain salts of aluminium, chromium, copper, iron, iodine, potassium, sodium, and tin.” This would explain the strong smell prior to washing the sheets.
If, on the other hand, the sheets had contained a high percentage of polyester, I would have assumed that dye sublimation had been the digital large format printing technology of choice.
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on Thursday, November 15th, 2012 at 5:05 pm and is filed under Large-Format Printing.
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