dye

Type of Colorant

Natural or Synthetic compound

A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber.

Both dyes and pigments appear to be colored because they absorb some wavelengths of light more than others. In contrast with a dye, a pigment generally is insoluble, and has no affinity for the substrate. Some dyes can be precipitated with an inert salt to produce a lake pigment, and based on the salt used they could be aluminum lake, calcium lake or barium lake pigments.

Dyed flax fibers have been found in the Republic of Georgia dated back in a prehistoric cave to 36,000BP. Archaeological evidence shows that, particularly in India and Phoenicia, dyeing has been widely carried out for over 5,000 years. The dyes were obtained from animal, vegetable or mineral origin, with none to very little processing. By far the greatest source of dyes has been from the plant kingdom, notably roots, berries, bark, leaves and wood, but only a few have ever been used on a commercial scale.

Natural Dye

The majority of natural dyes are from plant sources – roots, berries, bark, leaves, and wood, fungi, and lichens. Textile dyeing dates back to the Neolithic period. Throughout history, people have dyed their textiles using common, locally available materials. Scarce dyestuffs that produced brilliant and permanent colors such as the natural invertebrate dyes Tyrian purple and crimson kermes were highly prized luxury items in the ancient and medieval world. Plant-based dyes such as woad, indigo, saffron, and madder were raised commercially and were important trade goods in the economies of Asia and Europe. Across Asia and Africa, patterned fabrics were produced using resist dyeing techniques to control the absorption of color in piece-dyed cloth. Dyes from the New World such as cochineal and logwood were brought to Europe by the Spanish treasure fleets, and the dyestuffs of Europe were carried by colonists to America.

The discovery of man-made synthetic dyes late in the 19th century ended the large-scale market for natural dyes.

Synthetic Dye

The first human-made organic dye, mauveine, was discovered serendipitously by William Henry Perkin in 1856, the result of a failed attempt at the total synthesis of quinine. Many thousands of synthetic dyes have since been prepared.

Synthetic dyes quickly replaced the traditional natural dyes. They cost less, offered a vast range of new colors, and imparted better properties to the dyed materials. Dyes are now classified according to how they are used in the dyeing process

Dyes vs. Pigments

Dyes dissolve in liquids. This gives them the ability to stain porous materials such as cloth or wood. They also tend to be very bright and produce transparent colors which don't separate, but they are strong bleeders. Dyes are notorious for being fragile when exposed to light and can react to pH changes. They can also react to salt, which is why some use the hybrid Lake colors instead. 

Pigments do not dissolve but instead disperse as very fine particles. They have very limited staining power on their own and need an additional binder to make the particles adhere once the liquid medium has evaporated or dried. Pigments are more deep than bright and produce more opaque colors that will separate over time, but do not bleed. They are also quite stable when exposed to lights, pH differences and chemicals.

The difference between (True) Dyes and (Hybrid) Lakes

A DYE is a distinct chemical that exhibits coloring power when it is dissolved. Dyes are water soluble, and will not mix with oils. Dyes can be purchased in a powder format or a less dusty version called "granular".

An ALUMINUM LAKE PIGMENT is an insoluble material that tints by dispersion. Lakes are produced from the FD&C Dyes and are oil dispersible (but generally not oil soluble) and thus can be mixed with oils and fats. They can also be dispersed or suspended in other carriers such as propylene glycol, glycerin and sucrose (water and sugar).

Lakes are produced in specific concentrations of dye. Thus, Red 40 Aluminum Lake is available in Low Dye (generally 15-17% pure dye) and High Dye (36-42% pure dye).

Because they are a hybrid of a pigment and a dye the pigment portion will tend to separate out of a material while the dye does not and tend to be more stable to light, pH and other factors than true dyes.

"Natural" and "Certified Organic" colors

So called “Natural” colors must be approved by the FDA for use in edibles, cosmetics and drugs, but are not subject to batch certification. Examples of "Natural" colors are beet , paprika , annatto, turmeric, titanium dioxide, caramel and cabbage to name but a few. It is important to note that there is no FDA definition of "Natural" with reference to food or ingredients.

The USDA’s National Organic Program certifies products as organic based on farming, handling, manufacturing, distribution and labeling practices. Certified Organic Colors are a select group of Natural Colors that contain ingredients that are in compliance with the USDA National Organic Program and which have been certified by an independent organic certification agency.

Colors used for Cosmetics

The color pallet for cosmetic products is broader than that available for food color. There are a wide variety of “D&C” Dyes and Pigments that can be used in cosmetics and drugs, but are not suitable for consumption. In addition, there are a wide array of pigments such as Iron Oxides and Ultramarines that do not require certification that can also be used in cosmetic products.

The dispersing mediums available for use in Cosmetics are much more varied than those available for edible products. Ingredients such as castor oil, mineral oil, and silicone can be used in cosmetics, but not foods.