3204.12 - Acid dyes, whether or not premetallized, and preparations based thereon; mordant dyes and preparations based thereon:

This HTS category, 3204.12, specifically covers acid dyes, whether or not premetallized, and preparations based on these dyes, as well as mordant dyes and their preparations. Acid dyes are anionic in nature and are typically applied from an acidic dye bath, binding to fibers containing basic groups, such as wool, silk, nylon, and modified acrylics. Metallized acid dyes contain metal atoms complexed within the dye molecule, often improving their light and washfastness properties. Mordant dyes require the use of a mordant (a fixing agent, usually a metal salt) to develop their color and bind to the fiber.

This category is distinguished from its sibling categories, such as disperse dyes (3204.11) or direct dyes (3204.14), by the chemical nature of the dye and its application method. Unlike disperse dyes which are non-ionic and suitable for hydrophobic fibers like polyester, acid and mordant dyes are designed for proteinaceous and polyamide fibers. Direct dyes, on the other hand, have an affinity for cellulosic fibers without the need for a mordant.

The subcategories within 3204.12 further break down these classifications by specific dye names, providing a granular level of detail for accurate import and export declarations. These subdivisions include specific acid dyes like Acid black 210 and Acid violet 19, as well as more complex listings of multiple acid and mordant dyes for ease of classification. The "Other" subcategory is reserved for acid or mordant dyes and preparations not explicitly listed, ensuring comprehensive coverage within this heading.