Acid Dyes

Acid dyes are water soluble anionic dyes that are applied to fibres such as silk, wool, nylon and modified acrylic fibres from neutral to acid dye baths. Attachment to the fibre is attributed, at least partly, to salt formation between anionic groups in the dyes and cationic groups in the fibre. Acid dyes are not substantive to cellulosic fibres. Acid dyes are used both commercially and by the studio dyer to dye protein/animal fibers such as wool, silk, mohair, angora, alpaca and some nylons and synthetics. Acid dyes require the use of an acid such as vinegar, acetic or sulphuric acid to set the colour.

Acid dyes sound scary to some novices, who imagine that the dyes themselves are caustic strong acids. In fact, the dyes are non-caustic, are in many cases non-toxic, and are named for the mild acid (such as vinegar) used in the dyeing process, and for the types of bonds they form to the fiber. Some of them are significantly more toxic than fiber reactive dyes, while others are even safe enough to eat, and are sold as food coloring.

Acid dyes fall into several classes:

• Leveling acid or strong acid dye,
• Milling or weak acid dyes, and
• Super milling or fast acid or neutral acid dyes.

Leveling Acid Dyes have been sold under the trade names of Kiton, Erio, Intracid, Sandolan, and Amacid, among others; they are also the acid dye component of all-purpose or union dyes such as Rit and Tintex, says Knutson. It's difficult now to find out which specific acid dyes fall into which of these dye classes, however. At least part of the reason is that the information is not particularly useful to the dyer.

Most histologic dyes are classified either as acid or as basic dyes. An acid dye exists as an anion (negatively charged) in solution, while a basic dye exists as a cation (positive charge). For instance, in the hematoxylin-eosin stain (H&E), the hematoxylin-metal complex acts as a basic dye. The eosin acts as an acid dye. A very large class of dyes containing acidic groups, such as the sodium salts of sulfonic acids or phenolic groups. They are more soluble and have less tinctorial value than basic dyes but they also have greater light fastness. They do not form lakes with tannin. Acid dyes are used in dyeing leather, paper, etc., and their particular value lies in their ability to produce brighter, more uniform colours. They are normally applied from an acid dye liquor (acetic, formic, or sulphuric acid); however, unless applied from a neutral or only slightly acid dyebath, i.e., pH of 6.0 to 7.0, their use is likely to result in acid degradation of the material dyed.

NAME OF THE DYESTUFF C.I. NO. NAME OF THE DYESTUFF C.I. NO. ACID BLACK AB ACID BLACK 210 Yellow M3RL Yellow 194 ACID BLACK 234 ACID BLACK 234 Yellow 2GLN Yellow 59 ACID BLACK MSRL ACID BLACK 194 Yellow GL Yellow 114 ACID BLACK 172 ACID BLACK 172 Yellow M5RL Yellow 204 ACID BLACK WA ACID BLACK 52 Yellow RL Orange 80 ACID BLACK 10BX ACID BLACK 1 Orange MRL Orange 142 ACID BLUE 92 ACID BLUE 92 Orange RL Orange 86 ACID BLUE MTR ACID BLUE 193 Scarlet ML Red 357 ACID BLUE S 5 R ACID BLUE 113 Red MBR Red 362 ACID GREEN PXC ACID GREEN 1 Red 2BL Red 219 ACID GREEN BS ACID GREEN 111 Bordeax MB Violet (90) ACID GREEN 20 ACID GREEN 20 Brown M2RL Brown 365 ACID RED 3BN ACID RED 131 Brown M2RL Brown 365 ACID MAROON V ACID RED 119 Brown MBL Brown 365 ACID FAST RED A ACID RED 88 Brown 2RL Brown 45 ACID RED SCARLET 3R ACID RED 18 Dark Blue MTR Blue 103 ACID RED GRS ACID RED GRS Orange G Orange 74 ACID RED RS ACID RED 114 Violet Brown B Red 184 ACID RED PG ACID RED PG Pink BE Red 186 ACID RED 97 ACID RED 97 Blue 2G Blue 158 ACID BRLL.RD 10B ACID VIOLET 54 Black T Black 11 ACID YELLOW GR ACID YELLOW 99 ACID YELLOW 5GN ACID YELLOW 110 ACID ORANGE II ACID ORANGE 7

ACID Miling Dyes AZO Dyes Metal Complex Dyes Nylon Dyes Textile Dyes Hair Dye Silk Dye