Naoharu Oyabu, printing consultant

Printing consultant Mr. Naoharu Oyabu.

The following two elements are crucial to streamlining the printing process. One is to reduce the color-matching process, which we introduced in issue , that is the OCS method, and the other is to reduce the combinations of stock pastes.

The printing pastes made from starch, tamarind-gum, CMC, guar-gum and sodium alginate are used in the printing factories. In Indonesian printing factories, combinations of three of the above stock pastes are mainly used. I am of the opinion that combinations of two of the above stock pastes are sufficient.

In an Indonesian factory, I actually produced polyester fiber printed by a combination between two of the above stock pastes and these printed goods looked in no way inferior to the ones printed by a combination of three of the above stock pastes. We have had a great number of these goods exported to Japan.

In a bid to lower raw material costs, to target the types of printing paste will be necessary. This sort of attitude will be important in Japan. When starch is used during printing processing, it is said generally, color value will become better, but it means color paste loses depasting properties. In the case that other pastes are used, the depasting properties become better than in the case of starch, besides color value will be decreased.
Each paste has its pros and cons.

For this reason, combinations of stock pastes are used in printing mills. On the other hand, the more combinations that become available, the more adjustments such as pH become necessary.

Concerning printing of polyester, combinations among three stock pastes are common in many Indonesian factories. Demand for reducing faulty printing by simplifying the supervision of the printing process is increasing.

Therefore, as for polyester printing, the combination between tamarind-gum, which is utilized as a main composite, and sodium alginate is used during the printing process in major printing mills.

Sodium alginate is added for leveling, accordingly, good printing quality can be expected by using color deepening agents.
Malic acid is often used for pH adjustment in Japan, however, citric acid is often used in Indonesian printing factories, because the price is low and the amount used is 0.5% against stock pastes.

If you give technological advice to countries offering lower labor costs, it is unreasonable to expect high levels from printing technicians, or from factory workers.

Unlike Japan, in-house education among technicians and factory workers doesn't go smoothly, therefore, enhancing the technological level as an organization is not easy. So, technological education should be basic.

When printing achievement reaches 90%, taking what I mentioned earlier into account, it is necessary to explain meticulously to them how preparations of color paste, printing, steaming and depasting for washing are related to one another.

In order to obtain good printings, if it were possible to produce a 100% solution to all the problems, it would be ideal, however, 100% understanding is not necessary. Too much concentration on achievement might cause faulty printing, which would put factory management in jeopardy.

In Indonesian printing factories, printing is carried out in large lots, accordingly, if color paste causes trouble, the loss caused by faulty printing will increase for a short period. If 90% becomes an approval line, the rate of faulty printing will decrease and this is more convincing to many factory managers.

In Indonesia many factories demand tamarind-gum at a low price. For this reason, it is impossible to prepare stock pastes in the same way that we do in Japan. Each factory needs to establish criteria for preparation of stock pastes. If you stay in Indonesia for a long period, you will understand the situation well.

Printing know-how does not work according to dyeing theory.

The actual printing process is different from dyeing theory. While the relation between dyes and materials is important in dyeing, there is printing paste and a screen mesh between dyes and fabric in printing, that is, a multi-layered filter exists between dyes and fabric.

In the case of dip dyeing, how dyes should be fixed onto fiber materials has to be considered. In short, the relation between dyes and fiber materials should be one to one. On the other hand, the relation between various dyes, printing paste, screen mesh and fiber material should be three to one in the case of printing.

When it comes to dip dyeing of blended fibers, the use of dyes will be more complicated, as will the printing itself. In issue , we introduced as an example of polyester fiber printing, the OCS method which makes color matching easier and on a parallel, reducing the combinations of three stock pastes to two will make the rate of faulty printing lower.

As a measure against higher production efficiency and reduction of faulty printing, the combination of two stock pastes is becoming more popular in Indonesia, and the simplification of stock paste combinations should be carried out in Japan as well.

Western printing mills tend to think much of physical factors while printing recipes in Japan have become more complicated and diversified over half a century.

Some critics say that Japanese printing processes have "excessive chemical additions", and I cannot deny these combinations have become complicated.

When I wonder if this method is sustainable in the future, I feel doubtful.

Considering the number of printing experts who are aging and retiring, the number of young experts is becoming far too small to fill their predecessors' shoes. Would-be printing experts are also decreasing in number.

For this reason, the Japanese printing industry is at the brink of collapse.

In future strategies, it will be necessary to re-establish printing know-how befitting an IT (information technology) oriented age.

As an approach to re-establish know-how, the following things are necessary.

1. Printing know-how should be simplified so that it can be digitalized.
2. The quality of printing should be improved rather than allowing the quality of printing to degrade.

In the case of excessive chemical additions, you will not know which paste leads to what result. So in a bid to avoid it, simplified combinations of stock pastes will help the analysis of the cause of the trouble derived from the conditions of printing, steaming, rinsing and drying.

There are many factors deciding the quality of printing. One of these factors is the printing paste in use on the fabric. Whether the paste is properly selected or not, decides the result of each printing. Until the so-called bubble economy burst, excessive chemical additions were popular to avoid faulty printing and this method was considered effective. However, this idea will not be feasible in the future, since the regulations on waste water in printing mills will become more rigorous. The amount of chemicals in waste water per liter will be scrupulously stipulated. To jump over these obstacles, the combinations of the printing pastes should be done between two rather than among three.

The most important thing in managing printing mills in the future is to make the rate of faulty printing as low as possible taking environmental matters into account. The compatibility between these two elements is inevitable. If you insist that you should cling to the conventional excessive chemical additions, you will face thorny issues.

The concept of printing materials produced in small-lots and on a wide-variety basis with QR (quick response) has become prevalent. If this printing is carried out with super QR, the rate of faulty printing will drastically shoot up.

If quick preparation work for printing produces a mismatch in the relation between the solid contents of color paste and the screen mesh, the shades on the surface and the back of the cloth will be different at the drying stage of the post-processing. That is, migration effects will become worse. The major cause comes from inappropriate combinations of stock pastes, because the drying speed by hot air in the drying chamber depends on the kind of paste.

Each paste has its own characteristic features. It has its own color development, permeability, transferability, fluidity, printability, depasting properties, chemical resistance and mesh dependence and these all depend on the type of paste.

If these characteristic features are disregarded and you make each paste combined and use it as a color paste, you will hit printing problems immediately.

Meticulous combinations of the three pastes will cause no problem, but the combination between two pastes will drastically reduce the risks.