Some years ago I have had the opportunity to suggest some experimental work on the evaluation of First-Strike. Very interesting paper has been presented by Dr. Fiebig (Denkendorf, Germany) in the second half of the eighties dealing this item in relationship with direct dyes.

An initial mention has been made in my paper (together with Oskar ANNEN, Roland WALLISER and Emil ENGELER) (see Bibliography, Nr. 139 and 145) in which it was explained the importance of initial pH in order to decrease the First-Strike of acid dyes on polyamide.

In the meantime we have had a lot of opportunities to face this behavior, not only in relationship with cotton and direct dyes, but in all the dyeing systems in which the temperature is not the main parameter for controlling the speed of adsorption of the dyes. As more interesting and more significant concerning possible errors in the process design:

• Cellulosic fibers: Direct and Reactive dyes
• Wool: All kind of dyes
• Polyamide: All kind of dyes

We are facing every day cases in which the importance of the First-Strike has been underestimated. That has been the reason developing Test Methods allowing to evaluate the magnitude of the First-Strike in each specific cases, as well the determination of the corresponding precautions in order to avoid its negative consequence.

The reasons can be explained in following form:

• The necessity to improve the reproducibility of the Color
• For that: The advantages to use low migrating systems
• For that: The convenience to design dyeing processes based on the controlled adsorption
• Consequently: The need to Improve the quality of effluents and a low impact on the physical properties of the dyeing goods
• And additionally: The better fulfillment of market requirements concerning fastnesses, specially wet fastnesses

Following these high-lines, the First-Strike achieves a big importance. So fare the migration has been the basis of the dyeing processes, it was some easier to balance the influence of the First-Strike. Bur using controlled adsorption processes, the migration can not more helps to compensate the terrific unlevelness of a big First-Strike.

The First-Strike can not be defined only as a constant of each dye, but depends of a lot of additional circumstances. For this reason it becomes very useful the analysis of First-Strike in relationship with following dependencies, as example:

1. Dye type and used concentration
2. Involved dyes in the recipe
3. Class of Substrate and history of the lots
4. Liquor ratio
5. Type and concentration of Auxiliaries
6. Electrolyte, pH

The specific actions depending of the evaluation of the lab trials, depends from the dyeing equipment, the available peripherics, the programming facilities, etc.

It is no always simple to establish the actions to be undertaken, and for this reason in the CARBOTEX software for process design, a very important part has been dedicated to the proposition of the best possible way to avoid the impact of First-Strike.

Non taking in consideration the big importance of the First Strike in the case of short liquor ratio values, is one of the reasons why the short liquor ratio has not yet becoming popular. See