History of Paint

 

History of Paint

The abundance and widespread use of paint in our daily lives makes it easy to take paint for granted. A look at the chemistry of paint leads to a better appreciation of its complexities.

Paint is a liquid composition that dries to an opaque film. It is composed of four basic types of ingredients: pigments, which are powders that give opacity and color; binders, which act like glue to hold the pigments together and cause the film to adhere to the surface being painted; liquids, which make the paint thin enough to spread on a surface, and additives, which perform special functions such as thickening, reducing mildew, and more.

Paints are generally classified as either solvent-borne or waterborne. Solvent-borne wall paints, such as oil paints, use a petroleum derivative (for example, mineral spirits) as the solvent. Waterborne paints use water.

Waterborne wall coatings prevailed from prehistoric cave paintings up to medieval wall paintings. Natural proteins were used as binders for the pigments. Tempera used egg whites as a binder; distemper, a similar waterborne paint, used animal glues from hides and hoofs. Whitewash used milk casein to bind lime (calcium hydroxide) onto Tom Sawyer's fictional fence. But all these exhibited poor washability and durability.

Linseed-oil-bound pigments — used by the ancient Egyptians, early Romans and Renaissance artists such as da Vinci and Michelangelo — were more durable, but were scarce until the linen industry expanded to provide ample flax seed, from which linseed oil was pressed. Hardening of the soft linseed oil films by rosin and adding volatile turpentine from the naval stores industry enhanced varnishes for Stradivarius violins, fine furniture and wooden floors. Turpentine was the only historic volatile organic solvent to control paint viscosities until the coke and petroleum industries distilled various naphthas.

These separate crafts came together only in the 1930s, when brilliant exterior waterborne paints enhanced and survived the 1933 Century of Progress Exposition in Chicago and the 1939-40 World's Fair in New York City.

World War II Brings Changes to Paint Industry

 

World War II Brings Changes to Paint Industry

During World War II, the paint industry geared up for defense production. Thousands of military items required paints, including camouflage paint for tanks; aircraft, ship, and truck finishes; and coatings for guns and bombs. Every soldier was equipped with many painted items, some of which had their own special finishes. In addition, construction equipment, water supplies, and electrical lighting systems necessary to a military campaign also required paint.

Sherwin-Williams, a leading paint manufacturer based in Cleveland, Ohio, worked to accommodate this defense conversion. Plant engineers converted old equipment to new manufacturing uses. Chemists experimented with old, almost forgotten oils and resins and treated them with modern processing equipment. Purchasing agents combed the country for raw materials so that shortages would not halt production.

Shortages affected every corner of life during the war, from women who gave up stockings because silk was unavailable, to paint manufacturers who were required to ration linseed oil, a common paint binder. These constraints led Sherwin-Williams to accelerate their research into new coatings concepts. Their chemists took casein, a milk protein used by the ancient Egyptians for making paint, and emulsified (or suspended) varnish in it. They then added a number of other ingredients, with water as the largest component, to create a water-based paint.

The result was Kem-Tone^© paint, a fast-drying emulsion that met with instant public acceptance and would ultimately become one of the best-selling paints in the United States. Kem-Tone^© paint became the first widely accepted waterborne interior wall paint with sufficient binding power to allow washability.

Developed by a team of Sherwin-Williams chemists, Kem-Tone^© paint did not depend on organic solvents (based on carbon, such as petroleum derivatives), and it reduced the required amounts of traditional binders, which were in short supply because of the war. Technologically, the chemists at Sherwin-Williams showed that it was chemically and commercially possible for a paint emulsified in water to produce a durable coating.

Kem-Tone^© was registered as a trademark on Sept. 23, 1941. In the next three years, more than 10 million gallons would be sold.

The widespread acceptance of Kem-Tone^© paint was accelerated by the simultaneous introduction of the hand-roller (called Roller-Koater™), which made application by do-it-yourselfers very easy. Here, too, wartime shortages played a significant role. Richard Adams, an engineer for Sherwin-Williams, invented and patented the roller as an alternative to brushes, which were in short supply because the war between China and Japan restricted the availability of hog bristles.

Kem-Tone^© paint and the Roller-Koater™ applicator ushered in a new era in the do-it-yourself paint market, which comprises about 50 percent of the architectural coatings (paints applied to residences) sold today. The innovative chemistry of Kem-Tone^© paint also opened the door to continued developments in waterborne paints, which account for approximately 80 percent of all the architectural coatings sold today.

Chemistry of Flavor

 

Chemistry of Flavor

Flavor is caused by receptors in the mouth and nose detecting chemicals found within food. These receptors respond by producing signals that are interpreted by the brain as sensations of taste and aroma. Certain taste and aroma combinations are characteristic of particular foods.

For example, a green apple tastes the way it does because the unique combination of chemicals found naturally within it are perceived by our mouths, noses and brains as the distinct blend of sweet and sour tastes and volatile aromas characteristic to the fruit. Identifying this chemical profile allows food producers to retain flavor in preserved green apples and, through synthesis of these flavor compounds, makes possible the production of candy, soda and other products using artificial green apple flavor.

The chemicals that produce flavors are notoriously difficult to study because a single natural flavor may contain hundreds or even thousands of component substances, and some of these substances are present in minute quantities. For example, one of the nine key aroma compounds found in pineapple is so potent that human subjects can detect it at only 6 parts per trillion—the equivalent of a few grains of sugar in an Olympic-size swimming pool. Understanding the components of flavor has become more important than ever with the modernization of food systems and the increased reliance on processed foods.

What is flavor?

 

What is flavor?

Taste plus smell equals flavor. We can detect five tastes (sweet, salty, bitter, sour and umami), and we can smell as many as 40 billion molecules. When they mix together in food, that can translate to more than a trillion possible flavors.

What does flavor have to do with chemistry?

Everything! We experience flavor in our brains, but it depends on taste and smell, which are chemical senses. That means we’re using our tongue and nose to sense molecules. Everything you taste—all the flavors you’ve ever experienced—are molecules.   

Can you tell how a molecule is going to taste from its structure?

We don’t have a perfect roadmap for flavor perception based on chemistry the way we do for color and sound, which are based on physics. But we do have a pretty good idea about a lot of things. For example, if you have a carbohydrate that’s not very big, there’s a good chance it’s going to be sweet. If a molecule is an acid, it’s almost definitely sour. 

Why do some plants produce seeds, roots, and bark that taste so good to humans?

We still don’t have a great idea about how to predict how a molecule smells just from its structure. We know from genetics that humans have around 400 types of smell receptors, but we’re still figuring out how they all work. We can make an educated guess about what a molecule is going to smell like, but it’s still a mystery how the brain translates signals from the smell receptors into the psychological experience of a smell or a flavor. 

Some people are using AI to analyze very large data sets to understand it. Others are taking a biology route by growing receptors in Petri dishes and seeing what kind of molecules they bind to. Some people are doing X-ray crystallography and structural studies to better understand the molecules themselves. Pretty much every area of chemistry has something useful to tell us about how flavor and smell work.

Synthetic Food

Synthetic Food

 In January 1976, the U.S. Food and Drug Administration (FDA) banned a popular and well-studied chemical used in food: Red 2. Food colorants have long been contentious, misunderstood and a target for chemistry researchers hunting for a breakthrough. 

Chemists first synthesized the molecule Red 2 in the late 1800s. They isolated the color from coal tar initially, then petroleum. Red 2 became the most popular dye in the food industry. Then, around 1970, the results of lab experiments seemed to challenge its safety. Public concern grew, and politicians urged the FDA to continue testing Red 2. Supporters of a ban claimed that the food colorant caused birth defects and cancer. Yet while further tests from FDA chemists proved inconclusive, the agency ordered food companies to stop using Red 2. As a result, the candymaker Mars paused making red M&Ms, although, ironically, red M&Ms did not contain the banned red dye—public anxiety had simply swelled so much that Mars wouldn’t risk losing business to any confusion.

As the U.S. government seeks additional bans on food colorants, both support and skepticism have again flooded in. In the final weeks of the Biden administration, the FDA moved to ban Red 3 from food and drugs. West Virginia has adopted the strictest ban on seven synthetic food dyes, and California has banned six.

Synthetic food dyes have just been better. Their colors tend to be more vibrant, and their chemical makeup tends to be more resilient against the (literal) pressures of food manufacturing: high temperatures, extrusion and pH changes. Natural dyes are more fragile in part because they are often extracted alongside sugar and other flavoring molecules that decompose under stress. This extra baggage also comes with an unwanted taste (unless a paprika-flavored sports drink sounds good to you). Natural food colors are often more expensive as well, and people tend to prefer buying brightly colored foods. 

However, public perception is that natural alternatives are considered safer. If the debate is a matter of health and death, then siding against synthetic food colors should be easy. But the truth is more complicated. 

“Natural” additives, such as annatto and saffron, can cause mild allergic reactions. Only a few synthetic colors have conclusive evidence of being toxic. Often, the dose required to cause harm is absurdly high. And while critics refer to synthetic food colors as “petroleum derived,” this label is misleading. “A 60 pound kid can eat 472 Skittles every day before hitting the [safe limit] for Red 40,” wrote immunologist Andrea Love in her newsletter ImmunoLogic. “A chemical behaves based on its identity, not its origin.”

The colorful dispute draws all sorts of criticism and support. Some candymakers want to keep using synthetic colorants; some consumer advocate groups fear the bans won’t be enforced. And research companies working on natural food colorants believe this is their moment.

Chemists can engineer natural dyes to with-stand heat and pH changes by enveloping them in polymers. They can also produce purer natural colors by tasking microscopic yeast to grow large batches in labs. This “fermentation-derived” color can also avoid unwanted veggie flavors. With-standing high pressures (like the force of pushing cereal through a shaping machine) is harder. But one company has invented a heat-stable blue gelatin powder based on extract from a Peruvian fruit called jagua. Jagua earned FDA approval in 2023.

In May 2025, the FDA approved three more natural colors as food additives: white calcium phosphate; a blue color from Galdieria algae; and butterfly pea flower extract, which can appear blue, purple, green or red, depending on acidity.

The red M&M remained discontinued until 1987. When it returned, Mars had switched to coloring it with Red 40—one of the synthetic dyes the FDA now wants to phase out. Which dye might be used next in the candy? Perhaps carmine, a food pigment made from crushed cochineal insects, which is already in use in European M&Ms.

 

Chemistry and society

For the first two-thirds of the 20th century, chemistry was seen by many as the science of the future. The potential of chemical products for enriching society appeared to be unlimited. Increasingly, however, and especially in the public mind, the negative aspects of chemistry have come to the fore. Disposal of chemical by-products at waste-disposal sites of limited capacity has resulted in environmental and health problems of enormous concern. The legitimate use of drugs for the medically supervised treatment of diseases has been tainted by the growing misuse of mood-altering drugs. The very word chemicals has come to be used all too frequently in a pejorative sense. There is, as a result, a danger that the pursuit and application of chemical knowledge may be seen as bearing risks that outweigh the benefits.

It is easy to underestimate the central role of chemistry in modern society, but chemical products are essential if the world’s population is to be clothed, housed, and fed. The world’s reserves of fossil fuels (e.g., oil, natural gas, and coal) will eventually be exhausted, some as soon as the 21st century, and new chemical processes and materials will provide a crucial alternative energy source. The conversion of solar energy to more concentrated, useful forms, for example, will rely heavily on discoveries in chemistry. Long-term, environmentally acceptable solutions to pollution problems are not attainable without chemical knowledge. There is much truth in the aphorism that “chemical problems require chemical solutions.” Chemical inquiry will lead to a better understanding of the behaviour of both natural and synthetic materials and to the discovery of new substances that will help future generations better supply their needs and deal with their problems.

Progress in chemistry can no longer be measured only in terms of economics and utility. The discovery and manufacture of new chemical goods must continue to be economically feasible but must be environmentally acceptable as well. The impact of new substances on the environment can now be assessed before large-scale production begins, and environmental compatibility has become a valued property of new materials. For example, compounds consisting of carbon fully bonded to chlorine and fluorine, called chlorofluorocarbons (or Freons), were believed to be ideal for their intended use when they were first discovered. They are nontoxic, nonflammable gases and volatile liquids that are very stable. These properties led to their widespread use as solvents, refrigerants, and propellants in aerosol containers. Time has shown, however, that these compounds decompose in the upper regions of the atmosphere and that the decomposition products act to destroy stratospheric ozone. Limits have now been placed on the use of chlorofluorocarbons, but it is impossible to recover the amounts already dispersed into the atmosphere.

The chlorofluorocarbon problem illustrates how difficult it is to anticipate the overall impact that new materials can have on the environment. Chemists are working to develop methods of assessment, and prevailing chemical theory provides the working tools. Once a substance has been identified as hazardous to the existing ecological balance, it is the responsibility of chemists to locate that substance and neutralize it, limiting the damage it can do or removing it from the environment entirely. The last years of the 20th century will see many new, exciting discoveries in the processes and products of chemistry. Inevitably, the harmful effects of some substances will outweigh their benefits, and their use will have to be limited. Yet, the positive impact of chemistry on society as a whole seems beyond doubt.

Energy and the first law of thermodynamics

 

Energy and the first law of thermodynamics

The concept of energy is a fundamental and familiar one in all the sciences. In simple terms, the energy of a body represents its ability to do work, and work itself is a force acting over a distance.

Chemical systems can have both kinetic energy (energy of motion) and potential energy (stored energy). The kinetic energy possessed by any collection of molecules in a solid, liquid, or gas is known as its thermal energy. Since liquids expand when they have more thermal energy, a liquid column of mercury, for example, will rise higher in an evacuated tube as it becomes warmer. In this way a thermometer can be used to measure the thermal energy, or temperature, of a system. The temperature at which all molecular motion comes to a halt is known as absolute zero.

Energy also may be stored in atoms or molecules as potential energy. When protons and neutrons combine to form the nucleus of a certain element, the reduction in potential energy is matched by the production of a huge quantity of kinetic energy. Consider, for instance, the formation of the deuterium nucleus from one proton and one neutron. The fundamental mass unit of the chemist is the mole, which represents the mass, in grams, of 6.02 × 1023 individual particles, whether they be atoms or molecules. One mole of protons has a mass of 1.007825 grams and one mole of neutrons has a mass of 1.008665 grams. By simple addition the mass of one mole of deuterium atoms (ignoring the negligible mass of one mole of electrons) should be 2.016490 grams. The measured mass is 0.00239 gram less than this. The missing mass is known as the binding energy of the nucleus and represents the mass equivalent of the energy released by nucleus formation. By using Einstein’s formula for the conversion of mass to energy (E = mc2), one can calculate the energy equivalent of 0.00239 gram as 2.15 × 108 kilojoules. This is approximately 240,000 times greater than the energy released by the combustion of one mole of methane. Such studies of the energetics of atom formation and interconversion are part of a specialty known as nuclear chemistry.

The energy released by the combustion of methane is about 900 kilojoules per mole. Although much less than the energy released by nuclear reactions, the energy given off by a chemical process such as combustion is great enough to be perceived as heat and light. Energy is released in so-called exothermic reactions because the chemical bonds in the product molecules, carbon dioxide and water, are stronger and stabler than those in the reactant molecules, methane and oxygen. The chemical potential energy of the system has decreased, and most of the released energy appears as heat, while some appears as radiant energy, or light. The heat produced by such a combustion reaction will raise the temperature of the surrounding air and, at constant pressure, increase its volume. This expansion of air results in work being done. In the cylinder of an internal-combustion engine, for example, the combustion of gasoline results in hot gases that expand against a moving piston. The motion of the piston turns a crankshaft, which then propels the vehicle. In this case, chemical potential energy has been converted to thermal energy, some of which produces useful work. This process illustrates a statement of the conservation of energy known as the first law of thermodynamics. This law states that, for an exothermic reaction, the energy released by the chemical system is equal to the heat gained by the surroundings plus the work performed. By measuring the heat and work quantities that accompany chemical reactions, it is possible to ascertain the energy differences between the reactants and the products of various reactions. In this manner, the potential energy stored in a variety of molecules can be determined, and the energy changes that accompany chemical reactions can be calculated.