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. Water soluable 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:
1. Leveling acid or strong acid dye,
2. Milling or weak acid dyes, and
3. Super milling or fast acid or neutral acid dyes.
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
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.
EINECS No.: 284-915-2
Type: Acid Dye
CAS No.: 84989-26-4
Minimum Order Quantity: 500 Kgs.