- January 14, 2022
- 7 minutes read
Pigment, varnish and dye. What are the differences?
Color plays a very important role in our lives and is often the criterion for choosing clothes, decorations, furniture, small accessories. However, few people think about the fact that it is not an inherent characteristic of every material.
The colors that surround us, in many cases, are due to natural and synthetic coloring substances – dyes and pigments. They differ in their chemical properties, origin and areas of application. Let’s take a closer look.
Dyes – properties, types and uses
Dyes are usually organic, derived from plants and insects. They can be easily obtained at home by boiling vegetables, fruits or parts of vegetables to a thick broth.
Dyes are soluble in water, oils and alcohol. Their characteristic feature is the ability to impregnate the dyed material, which is why they are used in the food industry, in dyeing fabrics, paper, wood, fur, hair and leather. In the dyeing process they penetrate the material and form weaker or stronger bonds with the fibers. They also have migratory properties – if you put colored soap on paper, for example, sooner or later the paper will also be colored.
Types of dyes
The most well-known type of dyes used in everyday life are food dyes. They are safe for consumption and, as the name suggests, are mainly used for coloring food. They give very bright and intense colors, but not very durable. They dissolve in water and are usually sold in liquid form.
Another type is synthetic fat-soluble dyes. These also have bright and vivid colors, but are more stable and do not dissolve in water, but combine well with paraffin, wax or stearin. They are used for coloring candles, plastics, gasoline, leather, rubber, technical fats, oils, household chemicals (lacquers, shoe creams, etc.). Sometimes they are used in the confectionery and cosmetics industry, but in this case such a dye must have the appropriate safety certificate. An important and unusual property of such dyes is their concentration – in some cases, the manufacturer recommends the use of 7 g to 10 g of dye per ton of material. For this reason, they reach the end consumer in diluted form, for example in paraffin or oils.
There are also dyes that are soluble in alcohol, acetone, acids, sulfur dyes, etc. As you can easily guess, their name indicates the property of dissolving in specific substances.
Examples of dyes
Natural dyes include:
- kraplak (alizarin) extracted from arrowroot
- indigo (indigo blue) from indigo berry, bird’s-foot trefoil and bird’s-foot trefoil
- carminic acid from cactus maggots;
- sepia from cuttlefish.
The method of calcination from organic raw materials can be used to obtain black coloring substances.
Pigment – properties, types and uses
Pigments are finely divided substances (mainly minerals) chemically neutral to the medium and insoluble in water. In paint, they are found in the binder (water, drying oil, nitrocellulose, etc.). If we talk about mineral paints, their properties depend more on the substrate than on the pigment, and it is the binder that provides the bond with the painted material. This means that the pigment itself does not color the material, but settles on its surface, covers it.
Pigments can be used in cosmetic production (e.g. for soaps, lipsticks and creams), for coloring cement and concrete, plastics, rubber and in the manufacture of paints. Mineral pigments give cloudy colors, albeit in a variety of shades, while synthetic pigments create a wide range of vivid and distinctive colors, including neon.
Types of pigments
Pigments can be divided into absorptive, metallic (particles of metals or their alloys), pearl (single-colored and multicolored), and fluorescent.
There is also a division according to the method of obtaining. So we distinguish pigments based on iron oxide, chromium oxide, lead, copper and carbon black.
Examples of pigments
The most well-known pigments are titanium dioxide, lead and zinc white, ochre, cinnabar, zinc, ultramarine, azurite, cobalt blue, Brunswick green, carbon black, coal, Frankfurt black and manganese brown
And what is lacquer?
When hearing the word “varnish,” most of us will think of the colored wax-like substance used to make decorative stamps on letters and documents. And rightly so. However, varnish is also a coloring substance, insoluble in water and most solvents. It owes its name to the process as a result of which it is created – lamination, i.e. precipitation of a dye from the solution.
So-called colored lakes are resistant to light and higher temperatures. They are used to color paper, fibers, and in the manufacture of paints (oil, glue, and printing).
Main photo: Pavel Czerwinski/unsplash.com