THE PURPOSE OF STAINS AND PAINTS
Almost every kind of surface, from drywall to concrete, needs protection from the elements. These damaging elements can range from raging blizzards to innocent looking sunlight on a bed room wall. The total thickness of the paint that ends up outside of your home is usually about one tenth the thickness of your own skin, and interior paint is even thinner. We ask a whole lot of that coating of skin. What it can do depends on a number of factors, including the quality and brand of paint or stain, and how well the walls are prepared and painted.
Paint and stain should be durable, resisting fading and abrasion and allowing repeated washings. Interior paint should go on with minimal spattering. An excellent interior stain or clear finish should resist fading, peeling, or yellowing, and also be easy to maintain, free of impurities or waxes which could collect dirt and make cleaning or recoating difficult. External paints should dry with a toughness that resists deterioration from all types of exposure, and an elasticity which provides for constantly expanding and contracting surfaces. With their deep penetration and amount of resistance to ultraviolet (UV) light, the stains and finishes on your home's exterior should give a similar high performance.
A Brief History of Paint and Stain
The oldest known paint was used by the painters of Lascaux, who ground natural pigments with water and a binder that may have been honey, starch, or gum. You might be wondering why these cave paintings have lasted thousands of years as the paint on the south area of your property is peeling after only three winters. Here's why: The frequent mild temperature, humidity, and dark interiors of caves are ideal chemical preservatives. Your home, on the other hand, is subjected to all varieties of weather and conditions.
The Egyptians knew as early as 1000 B.C. that paint could protect as well as decorate. Beeswax, vegetable oils, and gum arabic were heated and blended with Earth and flower dyes to paint images that have lasted a large number of years. The Egyptians used asphalt and pitch to preserve their paintings. The Romans later used white lead pigment, creating a formula that could exist almost unchanged until 1950.
The Chinese used oil from the Tung tree to cement the Great Wall, and to preserve wood. The Chinese used gums and resins to make advanced varnishes such as, shellac, turpentine, copal, and mastic. The formulas and applications for those varnishes also changed little over the centuries.
Milk paint goes back to Egyptian times, was widely used until the late 1800’s when oil-based paints were introduced. Odorless and non-toxic, milk paint today is being revived as an excellent interior paint. Cassein, the protein in milk, dries very flat and hard, and can be tinted with other pigments. Like stains, milk paint needs to be sealed with a wax or varnish, and is also very durable.
Fashioned from hogs' bristles, badger and goat hair, brushes also changed little for many centuries. Bristles were hand bound, rosined, and greased, then hand laced into the stock of the brush. Hog's hair brushes, called China bristle brushes, remain a preferred brush for oil-based paints.
Pigments originally originated from whatever bore a color, from ground up Egyptian mummies to street dirt. Most mineral or inorganic pigments originated from rust, potassium, sea salt, sulphur, alum (aluminum), and gypsum, along with others. Some extravagant works incorporated precious stones such as lapis lazuli. Hundreds of organic and natural pigments from plants, insects, and animals constructed the rest of the painter's palette.
Paints and stains changed little from the time of the Pharaohs to the Industrial Revolution. A book on varnishes publicized in 1773 was reprinted 14 times until 1900, with only slight revisions. However, the colder climates of northern Europe did bring about the necessity for more durable paint, and in the 1500s the Dutch artist Jan van Eyck developed oil-based paint.
Starting in the Middle Ages lead, arsenic, mercury, and different acids were used as binders and color enhancers. These and other metals made the mixing and painting process dangerous. Paints and varnishes were usually blended on site, where a ground pigment was mixed with lead, oil, and solvents over sustained high heating. The maladies that arose from harmful exposure were common amongst painters at least until the late 1800s, when paint companies started to batch ready mixed coatings. While exposure to contaminants given off during the mixing process subsided, exposure to the harmful materials inherent in paints and stains didn't change much before 1960s, when companies ceased making lead based paints.
World War I forced the U.S. painting industry to modernize. Manufacturers had to discover a replacement for the natural pigments and dyes that came from Germany. They began to synthesize dyes. Today many pigments and dyes are chemically synthesized.
Inventions in the painting industry have extended well beyond pigments. Water-based latexes have gained in popularity as a safe, quality alternative to oil-based paints. Latexes have evolved from simple "whitewashes" to highly advanced coatings that can outlast oil-based products. Both oil-based and latex coatings are emerging every year with notable improvements, including the ground metal or glass that's now added to reflect damaging UV light.
A milestone in the evolution of coatings occurred in the early 1990s with the introduction of a fresh class of paints and stains known as "water borne." Created by the necessity to comply with stricter regulations, water borne coatings decrease the volatile organic ingredients, or VOCs, within standard paint and stains. Toxic and flammable, VOCs evaporate as a coating's solvent dries. They could be inhaled or absorbed through the skin, and create ozone pollution when exposed to sunlight.
THE CHEMISTRY OF PAINTS AND STAINS Paints and stains contain four basic types of materials: solvents, binders, pigments, and additives.
Binders and Solvents
Solvents will be the vehicle or medium, for the substances in a paint or stain. They determine how fast a coating dries and how it hardens. Water and alcohol are the primary solvents in latex. Oil-based solvents range from mineral spirits (thinner) to alcohols and xylene, to napthas. The solvent also contains binders, which form the "skin" when the paint dries. Binders give paint adhesion and sturdiness. The expense of paint is based in large part upon the grade of its binder.
Because water is the vehicle in latex paint, it dries quickly, allowing for recoating the same day. The odor that you see when using a latex paint or stain is the "flashing," or evaporation, of the binder and solvents. The binders in latex are minute, suspended beads of acrylic or vinyl acrylic that "weld" as the paint dries. Latex enamels contain a higher amount of acrylic resins for higher hardness and durability.
Alkyds and oil-based paints are basically the same thing. The word alkyd comes from "alcid," a combo of alcohol and acid that acts as the drying agent. Both have the same binders, which might include linseed, soy, or Tung oils. Oil based and alkyd enamels may contain polyurethanes and epoxies for extra hardness. Alkyd paints come in powerful combinations such as two part polyester-epoxy for professional use and a urethane revised alkyd for home use. Urethane boosts durability.
Water borne coatings use a two part drying system: water is the drying agent, and oils form a hard-drying resin. These new coatings match and sometimes out perform their oil-based cousins. They resist yellowing, are stronger, require only water clean-up, have little odor, and are non-flammable. One disadvantage: They swell hardwood grain and require sanding between coats.
Pigments; Stain and Paint
Pigments will be the costliest component in paint. Besides providing color, pigments also impact paint's hiding power - its ability to protect a similar color with as few coats as you possibly can. Titanium dioxide is the primary the most expensive ingredient in pigment. Top quality paints not only have significantly more titanium dioxide, but also more finely ground pigment. Inexpensive paints use coarsely ground pigment, which doesn't bind well and washes off more easily.
Additives; Paint and Stain
Additives determine how well a paint contacts, or wets, the surface area. They also help paint flow, level, dry, and resist mildew. Oil is the surfactant, or wetting agent, in oil-based paint. These paints have a natural thickness and capability to flow and level; they go on smoother than latex and dry more slowly, so brush stridations have a chance to level out. That is why oil-based paints have a tendency to drip on vertical surfaces more than latexes do.
Latex paint has been playing catch up with oil-based paint over the years. Today many latexes outperform oil-based paints and primers, because of thickeners, wetting agents (soapy substances that are also called surfactants), drying inhibitors, defoamers, fungicides, and coalescents. Defoamers keep latex paint from bubbling and leaving pinpricks (called "pin holing") in the paint as it dries. Bubbling is brought on when the soap wetting agent rises to the top as it dries. The better the paint, the less pin holing you should have. It used to be that if latex paint was shaken at the paint store you had to allow it to settle for a couple of hours. That is definitely no longer the truth with better paints, which may be opened and used right out of the shaker with no danger of pin holing.
Coalescents help latex resins bond, especially in colder weather. Oil-based paint, since it dries slowly and resists freezing, can adhere and dry in temperatures from 50°F to 120°F. With added coalescents and, contrary to popular belief, antifreeze, some latexes can be applied in the same temp range, and even lower. Some outside latexes can be securely applied at temps at only 35°F. Companies including Pratt & Lambert, Pittsburgh Paint, and Sherwin Williams have removed the surfactants to help their latex paints go on in lower temperature. As the wetting agents have been removed, the latex dries faster.
UV blocking additives have been added to paints and stains to help slow deterioration. Sunlight is responsible for much of the break down of any covering. It fades colors, dries paint, and adds to the expansion and contraction process that makes paint crack and peel off. UV blockers in paint may consist of finely ground metals and ground glass which is now being added for even more reflection of natural sunlight.
If you stay in an area with lots of humidity, rain, and insects, you may want to consider adding a biocide or fungicide to your paint. Biocide deters insects, and fungicide counters mildew. Many coatings already contain some fungicide, but only in small concentrations because of strict interstate regulations.
Sound Quality Painting
824 90th Dr SE suite B
Lake Stevens WA 98258
(425) 512-7400
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