Paint can add or detract from the value of your home. Your need to update and the changing moods of what’s popular might prompt you to repaint. When it comes to color, what’s in and what’s not will change and this is a good reason to not lock yourself in with siding or paneling that can’t change with the times. Instead, get used to watching paint dry.
Paint has a function beyond beauty–it protects a surface from damage, degradation by light and weather, and corrosion.
Paint was developed by the first chemists, the ancient Egyptians. The first pigment known was blue, which they made from bluegrass. Gum arabic, made from acacia trees, was another ancient component of paint. (It is also used in foods.)
Sometimes, a primer is used to seal the surface and add initial pigment before painting resulting in fewer coats of paint later. One component of a primer might be barium sulfate–the same thing used in a barium enema–or titanium dioxide. Even PVC can be in a primer.
Paint has three major components: pigments, binders, and thinner.
After paint is brushed on a surface, the thinner (also sometimes called a carrier) evaporates, the binder senses other, similar molecules growing closer, reacts with them and hardens as it dries. As it hardens it binds the pigment to the surface.
Bubbles can form in the paint, particularly if it is sprayed or if the paint is cheap, old, or shaken. Bubbles tend to wiggle through the paint until they group together and form in corners. Anti-foam agents can be added to paints when they are manufactured to prevent this. Other ways to prevent bubbles are to make sure you have the proper roller for the wall texture and to avoid painting in high humidity.
The binder plus the thinner is known as the paint vehicle, which is used to classify paint as either oil-solvent base or latex/acrylic (plastic) water-base. For chemical formulas of paints and primers, go here. And here.
Until the early 1950’s, the binder in paint was principally natural oils-tung, fish, and linseed. Then came latex in 1949. Within 5 years, 7% of all residential paint sales were latex. Today, 80% of all household paint is water-based. Water-based paint is more environmentally friendly than oil-based paint and provides for easier cleanup. Water-based paints used to be considered slightly inferior to oil-based when it came to durability but this is no longer the case. However, some painters consider them less glossy.
Even with the water vehicle, paint should be used in a well-ventilated area. Although water-based paint dries in an hour and can accept a second coat in four hours, it is slow to totally cure (bond with itself fully). This can take up to a month. In other words, it won’t be at its hardest for 30 days and should be treated carefully until then.
Any old house probably has seen lead paint. Older homes were painted white with linseed oil and lead oxide in a high concentration. Anything old that was once white was once lead. I’m a chemist and I like to test for lead. I haven’t found it in my home’s interior but have detected it in the outside paint in an inconsistent concentration. Lead dust is dangerous and lead paint chips laying around and on the soil present a hazard. Keep in mind that lead is a stable element. As such, it won’t change into anything less harmful. Lead should be painted over or if scraped off, should be wetted before being scraped and all chips should be put in a plastic bag and (in Iowa) treated like municipal garbage.
These days, the primary paint pigment is titanium dioxide (white). Colors are added to the titanium dioxide and they might be mineral or more commonly today synthetic organic. (NOT the same as natural.)
The color of paint is a matter of personal choice. Some claim that colors will affect your mood. I for one want to make paint companies work for my money and like bright vibrant colors. This year’s color of the year is what I painted my bedroom when I was 13. I might fall in love with it again. It reminds me of the first synthetic pigment–mauve.
One question you may have is if it is worth it to buy cheap paint. Consider that cheap paint doesn’t have more pigment, just more thinner. What type of finish should you buy? Low sheen paint hides imperfections and is good for low traffic areas and ceilings. High-sheen paints are more durable and contain more binder vs pigment.
Unopened paint will keep its properties for ten -fifteen years. Opened water-based paint lasts for about two years although some say longer. Old paint gets lumpy. Binder particles find each other and cling together, and old paint might even grow mold or bacteria. What should you do with unused paint? If you can’t give it away, recycle it, or use it up, put it in your municipal waste. (This is for water-based paint only.) Solidify it first–kitty litter or newspaper can help. Keep in mind that new advances have made paint even better so there is not much incentive to save old paint.
Catherine Haustein 
I love your posts….so full of information I did not already know. Thanks
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