Aniline printing - 100 Years Later

Material Science

Flexography evolved from a primitive printing process known as "aniline printing." In the early 1900s, this printing process took root to print flexible substrates using inks that were based on aniline-based dyes.

Although the earliest use of aniline printing can be traced to 1860, the first patent for an aniline press was issued in 1908.

From the very start, it was not considered a quality printing process compared to letterpress, lithography, or rotogravure. However, it provided quick ink drying to increase the speed of printing produce bags in a continuous operation.

Windmoeller & Hoelscher GmbH of Germany produced some of the first aniline presses in 1914.

The fast-drying characteristic of aniline printing inks allowed quicker processing and shipping. Thus, the corrugated industry was one of the first to utilize this process in the early 1920s and 1930s.

Introduction of the anilox roll and molded rubber printing plates provided the needed improvements to bring this printing process forward.

During the 1940s the aniline process showed its versatility as it proved capable of handling many of the new packaging films, including cellophane and PE.

In 1952, to remove the "aniline" part of its name and make it more acceptable to the flexible packaging food industry, the name of this printing process was changed to the "flexographic process."

Flexographic printing is based on the use of low-viscosity printing inks similar to those of roto- gravure. The high tack of lithographic inks proved impractical for printing thin flexible substrates. The key advantage of flexo and gravure inks is they have very low tack and dry quickly, making them well suited for printing on thin flexible substrates.

It was inevitable flexography would be competing against rotogravure. Although both processes use low-viscosity printing inks, flexo presses can be designed around a central drum that can support thin flexible substrates, which can be printed without the necessity of going through a high- temperature drying oven between each color. This means better register can be maintained on temperature-sensitive substrates, since the central drum temperature can be held constant.

Flexography and rotogravure have been in a competitive dance since the mid 1970s.

The quality of flexography has proved to be competitive to rotogravure in some package printing sectors, as well as to some lithographic printing.

Flexo is well suited for printing flexible packaging products with either solvent or water-based inks and now radiation-curable inks.

The success of water-based and UV-curable flexo inks made the process a major compliance alternative to solvent recovery or incineration; gravure was not as successful using either water-based or UV technology.

Flexo's cost advantages, as well as the ability to print with water-based and UV technology, clearly put this printing technology into the lead as we entered this century.

However, as flexography has grown in sophistication, so has its cost. Thus, flexo presses have lost some of their original economic advantages. A high quality, wide web press with all the bells and whistles can cost a lot of money.

And, while flexographic printing costs continue to grow, rotogravure - always known as the high-priced process - has been able to cut costs over the years. The result: It is no longer automatic that flexo printing is a cheaper process for a given job. You need to do your homework and price it carefully.

Worldwide, there is a great deal of gravure printing being done, and the low cost of rotogravure printing in third-world countries can compete with high quality flexographic printing in the US.

The net result of all this change has been that both printing processes have moved toward the center in terms of cost and performance. Run lengths are shorter, quality is up, and flexibility is in. In some cases, presses offer both flexo and gravure stations to optimize this flexibility.

The process once known as "aniline" today stands as the most versatile printing process, and it continues to evolve. It's not rotogravure and it's not lithography. It is its own unique printing process, and it has grown to be a major player in the flexible packaging printing sector.

Dr. Richard M. Podhajny has been in the packaging and printing industry for more than 30 years. Contact him at 267/695-7717; This email address is being protected from spambots. You need JavaScript enabled to view it..

To read more of Dr. Richard M. Podhajny's Material Science columns, visit our Material Science Archives.

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