Unexpected ink and ghosting

Find out the interaction between cotton dyes and specific plastisol products.

Competition at home and abroad has forced textile screen printing companies to have more cost awareness than ever before. In order to ensure that the budget does not overrun, companies are constantly looking for lower-cost supplies and materials. Low prices do not always mean low quality. As an operator, it is necessary to know that the composition and materials of clothing are constantly changing and not necessarily always better. To maintain quality to a certain level, the quality of the materials to be printed must be tested and monitored on a regular basis. This is the only way to ensure that the dyed products shipped out meet the needs of customers.

This article will examine the structure of fabrics, especially those that have been processed with certain dyes. As we have seen, this is a side that we can barely control in production, but it is also a very important aspect of our success.

Fabric dye

It is usually printed on two major fabric materials: 100% cotton and 50/50 cotton/polyester blends. Let's take a look at the interaction between dyes in cotton clothing and plastisol inks used in printing.

Pure cotton dyes are aqueous, and the dyeing process is accomplished by soaking hydrophilic (water-absorbing) cotton fibers in a water-repellent dye. Just as we inadvertently put red cotton T-shirts and white clothes into the washing machine, these water-soluble dyes will make our white clothing materials pink.

One of the reasons why 100% cotton garments are so common in textile screen printing companies is because the fabric dyes do not have ink spillage problems on the printed ink film. Because the dyestuffs used on cotton materials are water-soluble, the plastisol inks we use are often oil-based, and the dyes and inks do not mix, so there is usually no spillage.

However, it is worth our attention: In the textile industry, from printing companies to soft product suppliers, they are constantly looking for ways to reduce costs in order to maintain their competitiveness. Compared to the blank fabrics we have purchased, these cost reduction methods often bring about some surprisingly serious accessories.

To illustrate this point, an example can be used to illustrate: dyed 100% cotton fabric overflowed during the printing process. A company printed and dyed a large amount of dark red 100% cotton fabric before printing on a cotton cloth using standard non-anti-overflow white ink. Based on experience, printing operators believe that fabric dyes do not transfer to the plastisol ink. However, this does not happen long after printing.

The final reason for this was the use of very inexpensive water-dispersible dyes in the dyeing of fabric materials. Therefore, these dyes can be mixed with the film of the plastisol ink, changing the appearance of the printed image. From a chemical point of view, water-based dyes and oil-based inks are completely incompatible, and dye transfer cannot occur. However, after some investigations and studies have found that the traditional dye transfer is not the culprit. In contrast, the printing staff finally concluded that the dye used in the fabric is heat-sensitive. In fact, the dye is sublimated from the fabric surface during drying and then mixed into the printing ink film.

In some cases, the problem was so severe that when the fabric came out of the drying device, the area where the graphic text was printed on the shirt was immediately detected. In the part where the effect does not appear immediately on the fabric, the dye has generally partially penetrated into the printing area and subsequently diffused on the surface.

Prevent ghosting

Although this situation was caused by the materials used, it caused some very interesting problems, some related and more common printing problems - ghosting and its causes. When the spill-resistant ink film is in contact with the cotton fabric, the middle anti-spill media will squeeze the dye out of the fabric adjacent to it, which is a ghost phenomenon. This problem usually occurs when fabrics are placed on top of one another.

For overlapping garments, the elimination of gases from the fabric and subsequent ghosting problems occurs mainly in two ways: one is when the higher temperature fabrics are stacked together, the spill-over medium (usually organic peroxides) Will be released from the thermal ink film in the form of a gas, causing the topmost heat fabric to fade.

The second case is when the surface of the cotton fabric is printed with an ink that is resistant to spillage and it has not completely dried and cured. In this case, the anti-spill component cannot be completely fused into the ink film, so it will sublimate from the ink film and enter or exist on the surface of any other fabric in contact therewith. As a result, the dye of the second fabric is bleached, giving rise to a "ghosting" effect similar to that of the first fabric. Once the anti-spilling component produces the above ghosting problem, the fabric loses its original effect.

The good news is that we have now found a way to avoid this. First, it is necessary to apply anti-overflow inks on 100% cotton fabrics. Most well-known and well-known fabric manufacturers do not cut corners on the dyes used. This means that the color of their fabric is stable and there is no need to use spill-resistant inks. However, if anti-bleeding inks are to be used, it must be ensured that these ink films have completely dried and cured. In this way, we minimize the possibility of vaporizing the dye-based media in the ink after printing to adjacent fabrics.

Another basic solution to avoid ghosting problems when using spill-resistant ink is to carefully control the printing process to minimize the thickness of the printed ink film. A thicker ink film requires more heat and time to dry and cure, which makes it more likely to dry and harden.

In order to obtain a thinner, more easily cured ink film, we must use a high-strength wire mesh, a minimum off-plate gap, and a minimum squeegee pressure. These parameters help to accumulate less ink and ensure that the ink is only in contact with the surface of the fabric. In this way, the contact area between the ink and the fabric is minimized and the possibility of ghosting is greatly reduced.

In general, dyes used in high-quality 100% cotton fabrics are safe and reliable, eliminating the need to print with spill-resistant inks. However, some companies have become accustomed to using anti-overflow inks on all fabrics. This is simply for ease of operation and standardization. This principle is not wrong, but if the ink film is not completely dry and solidified, ghosting may occur.

A very effective solution is to use inks that do not contain spill-resistant ingredients when printing 100% cotton fabrics, and spill-resistant inks when printing 50/50 fabrics. If you have problems with spillage on your cotton fabric, consider using an ink that resists spillage.

There is also a more sensible way to avoid this spillable fabric from the outset. The method of avoiding the use of such inferior 100% cotton fabrics is to further understand fabric manufacturers, and the fabrics are tested according to conventional methods.

An effective way to detect dye quality is to print a thin layer of white plastisol ink that does not contain spill-resistant ingredients on the surface of the problematic 100% cotton fabric and then heat the sample. As long as the dye on the fabric is vaporized onto the ink film, transparency will immediately appear, warning you of the possibility of this problem. Then you can decide whether to use anti-bleeding ink or change to a fabric supplier.

in conclusion

Although few 100% cotton fabric dyes will overflow, there may be a printing problem that may result in the loss of an important customer and waste. Controlling the printing process, printing with the smallest ink film thickness, conducting proper testing, and using the right product for the job all help to avoid these problems.