THE FUNCTION OF PAINTS AND STAINS
Nearly every kind of surface, from drywall to concrete, needs protection from the elements. These dangerous elements can range from raging blizzards to innocent looking sunlight on a bed room wall. The full total thickness of the paint that ends up on the exterior of your home is usually about one tenth the thickness of your skin, and interior paint is even thinner. We ask a lot of that layer of skin. What it can do will depend on a variety of factors, like the quality and brand of paint or stain, and how well the surfaces prepped and painted.
Paint and stain should be durable, resisting fading and abrasion and allowing repeated washings. Interior paint should go on with reduced spattering. A quality interior stain or clear coat should resist fading, peeling, or yellowing, and also be easy to maintain, free from impurities or waxes that could collect dirt and grime and make cleaning or recoating difficult. External paints should dry with a toughness that resists deterioration from all sorts of exposure, and an elasticity that allows for constantly expanding and contracting surfaces. With their deep penetration and level of resistance to ultraviolet (UV) light, the stains and finishes on your home's outside surfaces should give a similar high performance.
A Timeline of Stain and Paint
The oldest known paint was utilized by the painters of Lascaux, who ground natural pigments with water and a binder that may have been honey, starch, or gum. You may be wondering why these cave paintings have lasted thousands of years while the paint on the south side of your house is peeling after only three winters. Here's why: The constant mild temperature, humidity, and dark interiors of caves are ideal chemical preservatives. Your home, on the other hand, is exposed to all types of weather and conditions.
The Egyptians knew as soon as 1000 B.C. that paint could protect as well as decorate. Beeswax, vegetable oils, and gum arabic were heated and mixed with Earth and vegetable dyes to paint images which may have lasted a large number of years. The Egyptians used asphalt and pitch to preserve their paintings. The Romans later used white lead pigment, making a formula that would 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 superior varnishes such as, shellac, turpentine, copal, and mastic. The formulas and applications for those varnishes also transformed 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 has been revived as an excellent interior paint. Cassein, the protein in milk, dries very even and hard, and can be tinted with other pigments. Like stains, milk paint needs to be coated with a wax or varnish, and it is very durable.
Created from hogs' bristles, badger and goat hair, brushes also evolved little for several 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 came from rust, potassium, sea salt, sulphur, alum (aluminum), and gypsum, amongst others. Some extravagant projects incorporated treasured stones such as lapis lazuli. A huge selection of organic and natural pigments from plants, insects, and animals composed all of those other painter's palette.
Paints and stains changed little from the time of the Pharaohs to the Industrial Revolution. A book on varnishes released in 1773 was reprinted 14 times until 1900, with only modest revisions. However, the colder climates of northern Europe have brought about the necessity for more lasting paint, and in the 1500s the Dutch artist Jan van Eyck developed oil-based paint.
Starting during 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 mixed on site, where a ground pigment was blended with lead, oil, and solvents over sustained high heat. The maladies that arose from poisonous exposure were common amongst painters at least until the late 1800s, when paint companies began to batch ready mixed coatings. While exposure to poisons given off through the mixing process subsided, exposure to the harmful substances 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 started 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 reputation as a safe, quality alternative to oil-based paints. Latexes have improved from simple "whitewashes" to highly advanced coatings that can outlast oil-based products. Both oil-based and latex coatings are emerging yearly with significant improvements, including the ground metal or glass that's now added to reflect harming UV light.
A milestone in the evolution of coatings occurred in the very early 1990s with the introduction of a new class of paints and stains known as "water borne." Created by the need to adhere to stricter regulations, water borne coatings decrease the volatile organic compounds, or VOCs, found in standard paint and stains. Toxic and flammable, VOCs evaporate as a coating's solvent dries. They could be inhaled or soaked up through your skin, and create ozone pollution when exposed to sunlight.
THE CHEMISTRY OF PAINTS AND STAINS Paints and stains contain four basic types of substances: solvents, binders, pigments, and additives.
Binders and Solvents
Solvents are the vehicle or medium, for the substances in a paint or stain. They regulate how fast a covering dries and how it hardens. Water and alcohol are the main 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 durability. The cost of paint is dependent 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 utilizing 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 greater amount of acrylic resins for higher hardness and durability.
Alkyds and oil-based paints are simply the same thing. The term alkyd is derived from "alcid," a blend of alcohol and acid that acts as the drying agent. Both have the same binders, which may 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 improved alkyd for home use. Urethane boosts toughness.
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 element in paint. In addition to providing color, pigments also have an effect on paint's hiding power - its capacity to cover a similar color with as few coats as is feasible. Titanium dioxide is the primary and most expensive ingredient in pigment. Top quality paints not only have more titanium dioxide, but also more finely ground pigment. Inexpensive paints use coarsely ground pigment, which doesn't bind well and washes off easier.
Additives; Stain and Paint
Additives determine how well a paint contacts, or wets, the surface area. In addition they 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 potential to flow and level; they go on smoother than latex and dry more slowly, so brush marks have more time to level out. That's why oil-based paints tend to drip on vertical surfaces more than latexes do.
Latex paint has been trying to catch up with oil-based paint over the years. Today many latexes outperform oil-based paints and primers, thanks to thickeners, wetting agents (soapy substances that are also known as 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 triggered when the soap wetting agent rises to the surface as it dries. The better the paint, the less pin holing you will have. It used to be that if latex paint was shaken at the paint store you had to allow it to settle for a few hours. This is certainly no longer the case with better paints, that can be opened up 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, because it dries slowly and resists freezing, can adhere and dry in temperatures from 50°F to 120°F. With added coalescents and, believe it or not, antifreeze, some latexes can be applied in the same temperatures range, and even lower. Some exterior latexes can be properly applied at conditions as low as 35°F. Companies including Pratt & Lambert, Pittsburgh Paint, and Sherwin Williams have removed the surfactants to help their latex paints be applied in lower temps. Because the wetting agents have been removed, the latex dries faster.
UV blocking chemicals have been put into paints and stains to help slow deterioration. Sunlight is responsible for a lot of the break down of any covering. It fades colors, dries paint, and increases the expansion and contraction process which makes paint crack and peel off. UV blockers in paint may consist of finely ground metals and ground glass which is currently being added for even greater reflection of natural sunlight.
If you stay in an area with plenty of humidity, rain, and insects, you may need 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.
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Lake Stevens WA 98258
(425) 512-7400
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