Ink

Ink is a liquid or paste used to apply color to surfaces such as paper, fabric, or skin. It typically contains a colorant (pigment or dye), a vehicle or carrier, and additives that influence drying, adhesion, and stability. Pigment inks use solid particles; dye inks use soluble colorants. The choice affects opacity, colorfastness, and compatibility with the substrate.

Inks are formulated for different media and applications, including writing, drawing, printing, and tagging. Common carriers include water (water-based inks), solvents or oils (solvent- and oil-based inks), and UV-curable or hot-melt systems. Industrial inks may also include binders to improve adhesion and durability.

In antiquity, carbon black inks were used for writing on papyrus and parchment. Iron gall ink emerged in the Middle Ages but could corrode manuscripts. The 19th and 20th centuries brought synthetic dyes, pigment dispersions, and modern printing inks, including inks for digital presses.

In printing, inks are formulated for processes such as offset, gravure, and digital printing, with attention to drying time, viscosity, and interaction with inks and plates. Performance attributes include color accuracy, opacity, lightfastness, water resistance, and longevity.

Today, formulations aim to minimize toxicity and environmental impact, with emphasis on durable, recyclable packaging and reduced volatile organic compounds. Some pigments may pose handling hazards; proper disposal and compliance with regulations are important in industrial settings.