Colorants (also spelled “Colourants”) are substances that are added to another material, such as paints, inks, textiles, plastics, ceramics, concrete and personal care products, with the purpose to change the color of that material.
Historically, humans would create primitive coatings with whatever they could find using improvised colorants like dirt, charcoal or naturally occurring iron oxides. Today, we are more sophisticated and create materials that can be used in modern colorants. These modern colorants can be based on dyes or pigments and they could contain water or solvent. So, colorants may be dry or in a liquid form. These colorants could also contain resins or additives that improve performance and durability. Therefore, colorants can come in many forms and variations.
Colorants work by absorbing varying amounts of light at different wavelengths and reflecting the remaining wavelengths to produce the color we see.
In transparent colorants based on dyes, the light is absorbed by the dye, but most of the light is usually reflected by the substrate. Dyes may start out as a dry material, but they are usually dissolved in water or solvent. Transparent colorants will help to ensure the substrate remains visible.
In pigment-containing colorants, light is absorbed and reflected mostly by the pigment in the colorant. Some pigment-containing colorants have a higher concentration of pigment to increase opacity. These colorants are used to hide the substrate or make the part opaque. These types of colorants are usually called pigment dispersions, pigment pastes or pigment preparations.
Other colorants may blend multiple pigments together to provide a finished color in a single colorant pack. This approach works well when coloring a material on a job site.
Liquid colorants are generally much easier and cleaner to use compared to dry colorants such as pigments. Dry pigments as supplied often contain large agglomerates varying by size and shape. By creating a liquid colorant, the energy applied to these agglomerates can reduce their overall size and narrow the range of aggregate sizes. The consistent liquid colorant bring a number of benefits:
Therefore, by creating a liquid colorant from a dry pigment, the colorant is easier to use and will provide consistent results time-after-time.
When in liquid form, colorants are typically added to another material by either volumetrically dispensing or adding them by weight through a manually or metered process. When in a dry form, colorants are more typically added gravimetrically. Recent advances in technology allow for some dry colorants to be dispensed volumetrically.
Manufacturers use colorants to add color to many types of materials, such as coatings, plastics and personal care. These include decorative and industrial coatings, thermoset composites, inks, thermoplastics, textiles, soaps and lotions. However, just about any material that has color will use some type of colorant.
Colorant properties vary greatly for coatings and plastics applications. The end application should be the driving factor in selecting the best colorant performance. Here are the key factors to consider:
The environmental impact of colorants varies. The paint and coatings industry has steadily been moving toward products that have less impact on the environment and consumer health.
A colorant defined as more “eco-friendly” typically contains lower levels of compounds called volatile organic compounds, or VOC’s. VOC is a broad term that includes compounds that are known to be harmful to people or the environment and are regulated by government and environmental agencies. Colorants considered environmentally friendly must contain low levels of these VOCs.
Biocides are a component of water-based colorants and paint. These components are designed to minimize biological growth. Hence, they could be harmful if people are exposed to them or they are released into the environment. The industry is looking for ways to reduce or eliminate these components in an effort to make them more environmentally friendly.
More recent trends include the incorporation of sustainable materials used in colorants such as resin and solvents, utilizing materials from renewable sources, such as plants. Other advances in colorant technologies include the use of infrared reflective pigments to lower surface temperatures, energy consumption and surface degradation caused by radiation from sunlight.