There are several steps in making paint, and over the years, manufacturers have perfected the art of making different products. Paint is one commodity that has become a significant part of housing construction, but if you are interested in the process, you will find that the raw materials can make or mar the paint. So, what goes in paint?
The most important materials that go into the paint are solvents, pigments, resins or binders, and additives. The solvents are the materials that make the paint easy to apply, and the resins ensure the paint dries. The pigments give the paint the colors it has, and the additives can serve as anything, from antifungal agents to fillers.
This article discusses the process of making paint and the various materials that go into it. The process may seem complex, especially if you are new to the field. But it is actually a straightforward process.
Paint-making involves several steps before the final product goes to the market. The first step is to create a design. Many people use industrial paints, but some consumers may require specific colors which are not readily available.
Some people may want paint that settles over time and offers superb coverage. Others may not be so patient and want paint that quickly dries. These require different preparation processes, and manufacturers must recognize their market before making large batches.
Next is to make a paste. Manufacturers buy bags of pigments in fine grain form and mix them with resin. There are different types of resins that paint manufacturers use, from natural to synthetic types.
Resin or binders mix with the pigment before it becomes a paste; the resin and pigments are solids. But before forming a paste, manufacturers add additives and a solvent. Sometimes, they add more than one solvent, depending on the intended paint type. Then, the mixture becomes a paste. The solvents are the liquids that turn the solids into a paste.
Most industrial paints go through a dispersion process. The same is true for some consumer paints. Once it gets the mixture, the paint plant passes it through a sand mill, which is a cylinder that shakes silica or sand particles in order to grind the particles of the pigment.
Initially, the pigment has difficulty mixing with other materials in the paste. But the dispersion process grinds the pigment particles and makes them smaller. That way, the sand mill can disperse them in the mixture. After distributing the particles, the next step is to filter the paste to remove the sand particles.
Most consumer latex paints with a water base do not pass through a sand mill for dispersion. They are usually processed in high-speed dispersion tanks. This method achieves the same results, but instead of sand, the tanks use toothed blades fixed to rotating shafts.
After the dispersion process, whether it is done in a tank or sand mill, the paste must go through a thinning process. Without it, there would be no paint as we know it. The paste goes into kettles with specific amounts of solvents, depending on the paint type. Then, the paste is further agitated to thin it and arrive at the final paint product.
When the paint is ready, the next step is to can it. Most paint plants automate this process, so it may not necessarily involve people. However, before the paint goes into cans, the paint pumps into a canning room.
The process involves rolling empty paint cans onto labels in a horizontal manner. Once the tags are on, the cans are set vertically so that the paint is pumped into them. Each filled can is covered with a lid by a machine, and another machine seals the lid by pressing it.
The cans have wires that form the handles, and a bailometer cuts the wires and shapes them. Then, it hooks them into the precut holes in the cans. After the final step of packaging the paint, a few of these cans go to the manufacturers’ warehouse for testing and quality control.
Canning is not the final step of making paint. The final product must undergo several tests to check its quality. Manufacturers use different measures to ensure they have the correct paint density, viscosity, dispersion, and grind. They apply some of the finished product on a surface to check its texture, drying rate and bleed resistance.
Spectral analysis and observation are used to check the color to ensure it meets the standard. It is also crucial to check the paint color’s resistance to fading, which typically happens due to exposure to the elements.
Manufacturers check this by applying the paint to two surfaces, exposing one to an arc light, and leaving the other unexposed. They compare fading after some time to determine if there is a need for improvement. For paint with gloss, manufacturers check it by the amount of reflection a painted surface gives off.
There are also tests to check the paint’s mar resistance. Once applied to a surface, the paint is allowed to dry before scuffing or scratching the dry coat. How well it holds up under pressure determines whether or not it passes the mar resistance test.
The paint is tested to check how well it hides surfaces or blemishes. The paint is applied on white and black surfaces to perform this test. The coverage ratio on both surfaces is measured, with .98 being an excellent score.
Then, there is a test for adhesion. A well-made paint must have an excellent ability to adhere to surfaces. Manufacturers apply the paint to a surface, allow it to dry, and make a crosshatch, calibrating it to 2 mm. They put a piece of tape over the crosshatch and pull it off. If the paint is good, it should remain on the surface and not come off with the tape.
A few other tests exist to check:
- Scrubbability of the paint
- Ability to hold up under different weather conditions
- Fire retardancy
- Settling rate
Materials that go into paint
Most of us do not stop to think about the materials that make paints what they are. An even fewer number wonder about the process of making them. There are four essential compounds that go into all paints: pigments, resins or binders, solvents, and additives. Each has a specific role, but they all work together to create excellent paint to meet specific design and decorative needs.
These are the compounds that provide the color you typically see in paints. In other words, pigments come in a variety of colors, and manufacturers choose the colors depending on what they need per time. They also provide a paint’s hiding attributes; the paint’s ability to hide surfaces depends on the type of pigment used.
Pigments are fine particles dispensed into the paint during manufacturing. There are two types of pigments: extender and prime pigments.
Extender pigments are usually not expensive and add bulk to the paint. They contribute to the dry hiding attributes of the paint but are ideal for controlling gloss. Common extender pigments are diatomaceous earth, zinc oxide, silica, and clay. Some of them do great in providing improved film performance when it comes to abrasion or scrub resistance.
Prime pigments are the more expensive types and produce excellent wet and dry hide. Titanium dioxide, in particular, provides the wet hide in paint and is usually costly. Colorants are also prime pigments and are responsible for the color you see inside a can of paint. Colorants come in two forms: inorganic and organic.
The inorganic form has a dull, rich-earth color, making it ideal for exterior applications. The organic form has bright colors and can be used inside a house. It may also work for the exterior parts but may not be ideal.
One of the vital attributes of paint is its performance, and binders directly contribute to it. They improve a paint’s ability to adhere, resist abrasion, retain gloss, be washable, and resist fade.
Manufacturers typically use oils such as soya oil and linseed oil to make oil-based binders. Traditional oil-based binders tend to have a hard and dry finish, enhancing adhesion, leveling, and flow. The downside is that they quickly oxidize and may turn yellow when used in light colors. Also, they may become chalky when applied to exterior parts.
These days, manufacturers use alkyd emulsion instead of alkyd binders. It still presents like oil-based binders but is easier to clean with soap and water. It performs better in general but may also have the same downsides as the oil binders over time.
These are liquids that make applying paint easy. They ensure the paint does not stick to the can but can go from there to the surfaces during application. The type of paint determines the solvent that goes in it. The solvent may be water if it is latex paint, but oil-based alkyd paint typically uses paint thinners or some other similar liquid.
Mixing the binders with the pigments does not produce the paint in the liquid texture you see in the paint can. It is only when a solvent goes into the mix that it has that liquid look. However, the volume of the solids – binders and pigments – determines what remains on a painted surface.
Solvents have their role, but solids make all the difference. Nevertheless, a can of paint is not necessarily top-quality simply because it has a higher percentage of solids than liquids. It still depends on the quality of materials used.
These are basically extra materials that add attributes to the paint. They can be anything, such as fillers or any antifungal agent. Some of the most commonly used additives are:
Biocides: They go in many latex paints and come in two types – mildewcides to keep mildew from growing and preservatives that stop bacteria from invading the painted surface. They can also be fungicides to prevent the growth of fungi.
Co-solvents: These are other liquids that boost the performance of water or any other solvent used. Co-solvents are excellent in helping the binders to form a good film, especially when used in cold weather. They also enable application by keeping the paint liquid enough until it is applied before it dries.
Surfactants: These are soaps that provide stability in the paint to prevent separation. They also encourage pigment dispersion in the liquid to give the paint better hiding power and color accuracy.
Thickeners: These are agents that help the paint to flow and level better, preventing splatters during application. They also make the paint thicker for better application.
Defoamers: They prevent the formation of bubbles in the paint. Typically, bubbles tend to form in the paint during production, when shaken at the tint center, and during application. In other words, defoamers keep them smooth.
How paint works
The simplest way to explain it is that the solvent evaporates and leaves the paint or lacquer behind. If the solvent remains, the paint will run. The binders or resins and pigments draw closer as the solvent evaporates, and when it is all gone, the solids meet and form a tough and abrasive-resistant coat in most cases.
Some paints initially look rough when it initially dries after application. This is typical in mineral-based alkyd paints with mineral turpentine as solvents. The turpentine evaporates and leaves behind an unattractive coat. However, the alkyd resin in the paint reacts to oxygen, and when it does, it polymerizes to form a hard and smooth coat. This hard coat ensures excellent adhesion.
There are several stages in making paint, all of which are complex. Paint is not just about picking the right color; the pigment may be great, but the binders also need to match it. The pigments and binders are the solids that make the paint what it is. They are what remain after the solvent evaporates and the paint dries. Additives give the paint the ability to perform extra and better.