Definition of Acid Dyes

The dyeing procedure, which is done in an acidic aqueous solution, is where the phrase "acid dye" originates. Acid dyestuff gets its name from two basic factors. The majority of these kinds of dyestuff are sodium salts of organic acids, and they were applied in a bath containing mineral or organic acids like sulphuric, acetic, or formic acid. Acidic conditions cause the positively charged amino groups in wool to be drawn to the negatively charged anions of acid dyes, which are anionic in nature.

Qualities of Acid Dyes:

The main qualities of acid dyes are:

• Acid dyes are water-soluble.
• These dyes are of the anionic variety.
• Usually, they are blended with simple dyes.
• Wool, silk, polyamide, and modified acrylics can all use these dyes.
• These colors are unsuitable for cellulosic materials because they have no affinity for cotton cellulose.
• They frequently dissolve in alcohol.
• The dye anion is what gives these dyes their vibrant hue.
• Acid dyestuffs are often decolored when they are treated with a reducing agent.
• The dyed acid colors are somewhat washable and exhibit good light fastness.

Application of Acid Dyes

These dyes are best suited for dying cloth and yarn, particularly carpet yarns, because of their outstanding level-dyeing qualities. Wool and silk are examples of natural textiles that can be dyed with acid dyes. Additionally, they are utilized to color polyamide. Since acid dyes are anionic, they will ionize in solution to form sodium ions as well as sizable colored ions that are negatively charged. They will therefore color any fibers that have positively charged spots for this reason.

Classification of Acid Dyes

Acid dyes are categorized based on their acidic power:

1. Neutral acid dyes: Also known as supra-milling or fast acid dyes, these dyes have medium to good wet fastness capabilities although some of them have poor light fastness in light shades. Numerous dyes are solely used as self-shades. These are applied to the fiber at a pH that is neutral or barely acidic.

2. Weak acid dyes: This category of dyes are made up of milling dyes. Although the light fastness of these dyes is just fair to bad, they have good fastness qualities.

3. Strong acid dyes: These dyes, which are also known as leveling dyes, are applied in a strongly acidic media, however, their wet fastness characteristics are a drawback. These dyes work well to create blends of colors.