Paint is, in the decorating world, the universal solvent. It can completely transform a space with almost no effort, and when compared to other remodeling practices, painting is phenomenally cheap. What is it that makes paint so special? Is there a secret within the composition of paint that gives the stuff so much power? Let’s take a look.
The History of Paint
For almost as long as human beings have been wandering the earth, we have been making paint. We have paintings, however crude, that are 20 to 25 thousand years old. The next time you are in Cantabria, Spain or Montignac, France, check out Altamira or Lascaux, respectively. There you can examine the evidence of some truly remarkable primitive paints.
The ancients were not particular about their composition of paint. They used what they had readily available, including minerals, rocks, other natural earth pigments, charcoal, lard, milkweed sap, berry juice, and even blood. The days of such resourcefulness have shifted to ready-made paint available on the shelves of hardware stores.
This shift really caught hold in 1867, when the patent for ready-made paint was approved. Such patents started a trend of paint factories popping up all across the nation in the mid-1880s. This kind of innovation and those we continue to make regarding the composition of paint make the substance widely available in nearly every color, finish, and characteristic imaginable.
Understanding the Composition of Paint
While the composition of paint has shifted slightly, at its core, paint is the same: pigments or dyes mixed into a vehicle that allows them to be applied. That vehicle is generally a liquid or kind of paste to accommodate easy spread, as we’ll discuss momentarily. In order to achieve the characteristic nature of paint we have come to expect, manufacturers make paint by combining four ingredients: solvents, pigments, resins, and additives.
Solvent
Think of the solvent as the broth that keeps the rest of the paint “soup” together. All the other components of paint are mixed together within the solvent, so it is helpful for the solvent to be a liquid of low viscosity. After paint has been applied to a surface, it evaporates, leaving behind the other components.
This second feature means that the best solvents are relatively volatile, including liquids like the aromatics: alcohols, esters, benzol, ketones, and acetone. Back in the fifteenth century, artists began to add drying oils to their paints to speed up the drying process. They were also responsible for the innovation of linseed oil as a solvent. It was the most commonly used solvent until the twentieth century when synthetic solvents replaced its use.
Pigment
When thinking about the composition of paint, pigment is usually what springs to mind. Pigment gives paint its color, and while the other components help to get it on the wall, pigment is the main reason to add paint. Ancient people, including the Chinese, Greeks, Romans, Hebrews, and Egyptians understood this, using natural oils and pigments such as red and yellow ochres, arsenic sulfide yellow, malachite green, and chalk.
We still have a supply of hundreds of unique pigments, both natural and synthetic. Their use heavily favors the synthetic side, especially because synthetic pigments tend to stabilize the entire mixture. However, we haven’t quite abandoned our roots, for most black pigment on the market is still made from carbon black.
Resin
Resin is sort of a hidden champion when it comes to the composition of paint. It is the glue which binds paint together. It is also responsible for paint’s ability to adhere to the surface being painted. From the earliest days of paint, people have understood that resins are required to make paint really successful.
In ancient Greece and Egypt, natural elements like egg albumen, gum arabic, beeswax, and lime were used. By the Middle Ages, people began to boil their resin with oil to increase the mixture’s miscibility. Today we still use oils like linseed, soybean, and coconut as natural resins, but we also take advantage of synthetic resins like polyurethanes, acrylics, epoxies, and alkyds.
Additives
The additives thrown into a mixture of paint are really a grab bag of goodies. The general category covers many different chemical components to give paint characteristics beyond color. Sometimes the additives are just meant to add body and substance to a mixture of paint without changing its properties. This is the case with aluminum silicate and calcium carbonate.
Other additives add an element of fun. Thixotropic agents improve paint’s ability to cover well, including agents with defoaming, anti-settling, anti-skinning, rapid-drying, or smoothing characteristics. Other additives block stains, resist scuffing, or kill mold. Which additives are included is entirely the prerogative of the manufacturer.
