Acid Dye

Definition and Overview

Acid dyes are a group of dyes that are dissolved in water and used in a dye bath adjusted to the acidic side. They bind to dyeable sites in the fiber and are mainly used for wool and silk, which are animal fibers, as well as nylon, a synthetic fiber. The term acidic in the dye name indicates the pH of the dyeing process, not that it dyes only fibers with acidic properties.

Characteristics and Expression

They make it easy to achieve everything from vivid hues to deep dark shades, and are used for dyeing that makes use of the luster, softness, and drape of wool and silk. However, the final color appearance and hand feel vary depending on the fiber type, yarn or textile structure, pretreatment, dyeing conditions, and after-processing.

Colorfastness against fading, rubbing, sweat, and light cannot be judged by the acid dye classification alone. Depending on the application, it is important to check the required test items and performance levels, such as wash fastness, rub fastness, perspiration fastness, and light fastness.

Main Applications

Used for sweaters, knits, scarves, shawls, blouses, dresses, and linings made with wool or silk. In nylon, they may be used for dyeing sportswear, innerwear, lace, socks, and similar items. What determines the appearance and wearing season of the material is not the dye, but the fiber blend ratio, textile structure, fabric weight, and finish.

Selection and Handling Notes

When selecting a textile, check not only that it is dyed with acid dye, but also the target fiber, blend ratio, desired color, colorfastness, and care label. In textiles blended with different fibers, the same dye may not dye evenly, or may create a differential-dyeing effect, so confirm in advance with color swatches and test rolls.

Wool and silk can change in hand feel and dimensions due to moisture, heat, rubbing, and alkaline detergents. For products that need shrinkage control, check whether shrink-resistant finishing has been applied and the washing conditions. In sewing, assume possible color transfer from dark textiles, and evaluate rubbing against accessories and sewing thread, as well as bleed during wet conditions, in advance.

• Since color differences may occur depending on the lot and dyeing conditions, manage lots during additional production.
• Before cutting, check the grain line and shrinkage rate of the textile, and if necessary, relax the roll and straighten the grain.
• When combining with white or light-colored linings, tapes, or accessories, check for color transfer due to wet rubbing.

Differences from Similar Terms

Reactive dyes are dyes that chemically bond mainly with cellulosic fibers such as cotton and rayon, and their suitable fibers and dyeing conditions differ from those of acid dyes. Disperse dyes are mainly for hydrophobic synthetic fibers such as polyester, and differ from acid dyes in that they dye by dispersing dyes that are difficult to dissolve in water.

Yarn dyed and piece dyed are process categories: whether dyeing is done at the yarn stage or after the textile is made. Acid dye is a type of dye, and it is used in either yarn-dyed or piece-dyed processes depending on the target fiber and production conditions.

Frequently Asked Questions