Yet if you spend enough time painting, you might wonder why paint behaves the way it does. Far from being an esoteric subject remote from all practical applications, the manufacture and makeup of paint begin to take on a significance that applies to your own home. For example, once you understand that latex paint contains a great deal of water—often approaching half of its total weight—you will understand why it is so important to paint in the right climactic conditions. If you were to paint a room with four gallons of paint, for example, consider that nearly two gallons of water on your walls need to completely evaporate before you can lay down a second coat of paint. But let that same paint rest for nine months in the basement and it tells a different story, revealing its true structure. On top is a liquid that veers toward clear and bears no resemblance to the representative color dot on the lid. Press the stick to the bottom and you will discover a thick, nearly impenetrable solid mass. Latex paint, the most widely used paint in homes by do-it-yourself homeowners, is composed of solids and liquids. All paint specifications state how much of the paint is solids or liquids. For example, in one gallon of flat paint, 57 percent of the weight might be devoted to solids. For paint on the other end of the sheen spectrum—semi-gloss—solids’ weight might drop to around 51-percent. Already it is evident how paint’s make-up applies directly to your own walls. If you have ever wondered why flat or matte paint has a chalky texture, it’s because of this: more solids.
Solvents: Vehicle for the Solids
Solvents are the liquid body of the paint, the vehicle that carries and dissolves the other ingredients. Water, often called the universal solvent, is used for latex paints. For oil-based paints, mineral turpentine is often used as the solvent. Solvents are the ingredient that account for paint drying time. For water-based latex paint, all of the water in the paint ends up on your wall, ceiling, or other work surface and must fully evaporate for the paint to cure. This is why humid and cold conditions adversely affect paint drying time and, at worst, cause the paint to fail.
Resins: Paint Binders
If water helps keep the solids in water-based latex paint solvent, it is the resins that bind everything together and help the paint dry after it has been applied to the surface. For many latex paints, these resins come in the form of acrylic emulsion polymers.
Pigments: Color
Pigments give paint its color. Pigments initially come in powdered form. For example, white pigment is titanium dioxide, black pigment is carbon black, and oranges and yellows are derived from metallic salts. At the paint store when you see the color dispersion machine squirting colors into the paint base, those water-borne pigments are called colorants.
Additives: Improving Paint Performance
Additives are a loose collection of other ingredients that supplement the paint, mainly to improve its physical properties. Additives might be added to the paint to smooth out brush strokes, inhibit mold growth, promote faster drying, or help the paint to resist sag. It is also possible for the product user, after purchase of the paint, to introduce additives. Penetrol and Floetrol are the brand names of popular additives that smooth down brush marks.
The Process of Making Paint
Measuring and Portioning
Raw liquid and dry ingredients are portioned out by bulk weight or by volume in calibrated vats, much like measuring out cooking ingredients in measuring cups.
Mill Base Creation
Raw pigments are crushed and dispersed, creating a dry substance called the mill base.
Letting Down
In a process called the let-down, resins, solvents, and additives are prepared in a different vat.
Combining
The mill base and let-down product are combined.
Shipment to Canning Area
Prepared materials arrive at the canning section by truck. Liquid materials are piped into storage silos or tanks and dry materials are brought into the receiving area of a warehouse.
Mixing
Materials are combined in tanks to create the paint.
Labeling
Empty paint cans arrive in the factory and are run through machines that apply labels to them.
Filling
Separate machines fill one-gallon paint cans and five-gallon paint cans.
Palletizing
Cans are sealed up, boxed, and the boxes are placed on pallets for shipment.
