3. Effective area and level dyeing

When the material transfers, an effective part of the dyebath is expressed as an average area of gross material because of the movement of the position of the minimum area. Then, the area of the dyebath which can be occupied by the material is called “the effective area”.

In dyeing machines such as cheese or beam, where the material is fixed and the dyebath is circulated, the effective area of material is equal to or less than the minimum area for yarn or fabric, because the minimum area does not move and the effective area does not expand.

When a yarn or fabric is excessively compressed, the minimum area for yarn or fabric decreases, which causes insufficient penetration of liquor leading to unlevel dyeing. (To avoid such a situation, an increase of the rate of diffusion is effective, which is attained by an increase of dyeing temperature or the use of a leveling agent).

On the other hand, in dyeing machines such as jet or winch, where the material is circulated, the material can move in the dyebath and the effective area varies according to the mechanical conditions.

A level dyeing can be achieved if the area of dyebath closely relating to the fiber becomes large enough for liquor exchange and the conditions where a mechanical dye liquor exchange is effectively attained is established.

Further, if the absolute area in a dynamic dyeing system can be close to that of a static state by the increase of the area closely relating to the fiber, the necessity of forced pass of dye liquor through the pores of the material may be decreased, and even distribution of the dye can be achieved with a mild circulation or a transfer of the material.