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 living room wall. The total thickness of the paint that eventually ends up outside of your residence 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 number of factors, like the quality and type of paint or stain, and exactly how well the areas are prepared and painted.
Paint and stain should be durable, resisting fading and abrasion and allowing repeated washings. Interior paint can go on with little spattering. An excellent interior stain or clear coating should resist fading, peeling, or yellowing, and also be easy to keep, free from impurities or waxes which could collect dirty residue and make cleaning or recoating difficult. Exterior paints should dry with a toughness that resists deterioration from all types of exposure, and an elasticity which provides for constantly expanding and contracting areas. With their thorough penetration and amount of resistance to ultraviolet (UV) light, the stains and finishes on your home's exterior should provide a similar high performance.
The History of Stain and Paint
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 a large number of years as the paint on the south part 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 house, on the other hand, is exposed 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 warmed and mixed with Earth and herb dyes to paint images that have lasted thousands of years. The Egyptians used asphalt and pitch to protect their paintings. The Romans later used white lead pigment, developing a formula that would exist almost unchanged until 1950.
The Chinese used oil from the Tung tree to cement the Great Wall, and also 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 evolved little in the following centuries.
Milk paint dates 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 alternative 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 covered with a wax or varnish, which is very durable.
Fashioned from hogs' bristles, badger and goat hair, brushes also improved little for several centuries. Bristles were hand bound, rosined, and greased, then hand laced in to the stock of the brush. Hog's hair brushes, called China bristle brushes, remain a preferred brush for oil-based paints.
Pigments originally came from anything that bore a color, from ground up Egyptian mummies to road dirt and grime. Most mineral or inorganic pigments came from rust, potassium, sea salt, sulphur, alum (aluminum), and gypsum, among others. Some extravagant projects incorporated treasured stones such as lapis lazuli. A huge selection of organic and natural pigments from plants, insects, and animals made up 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 shared in 1773 was reprinted 14 times until 1900, with only slight revisions. However, the colder climates of northern Europe did bring about the need for more lasting paint, and in the 1500s the Dutch designer Jan van Eyck developed oil-based paint.
Starting in the Middle Ages lead, arsenic, mercury, and various acids were used as binders and color enhancers. These and other metals made the mixing and painting process unsafe. Paints and varnishes were usually combined on site, where a ground pigment was blended with lead, oil, and solvents over sustained high heat. The maladies that arose from dangerous exposure were common among painters at least before late 1800s, when paint companies began to batch ready mixed coatings. While exposure to poisons given off during the mixing process subsided, exposure to the harmful substances inherent in paints and stains didn't change much until the 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 originated from Germany. They began to synthesize dyes. Today many pigments and dyes are chemically synthesized.
Enhancements 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 yearly with distinctive improvements, such as 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 category of paints and stains known as "water borne." Created by the necessity to comply with stricter regulations, water borne coatings reduce the volatile organic materials, or VOCs, found in standard paint and stains. Harmful and flammable, VOCs evaporate as a coating's solvent dries. They could be inhaled or consumed through the skin, and create ozone pollution when subjected to sunlight.
THE MAKE UP OF STAINS AND PAINTS Paints and stains contain four basic types of materials: solvents, binders, pigments, and additives.
Solvents and Binders
Solvents will be the vehicle or medium, for the substances in a paint or stain. They regulate how fast a coating dries and exactly how it hardens. Water and alcohol are the key solvents in latex. Oil-based solvents range between mineral spirits (thinner) to alcohols and xylene, to napthas. The solvent also includes binders, which form the "skin" when the paint dries. Binders give paint adhesion and sturdiness. The cost of paint is dependent in large part upon the quality 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 include a greater amount of acrylic resins for greater hardness and durability.
Alkyds and oil-based paints are basically the same thing. The term alkyd comes from "alcid," a combo 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 industrial use and a urethane altered alkyd for home use. Urethane boosts strength.
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 more durable, require only water clean-up, have little odor, and are non-flammable. One disadvantage: They swell real wood grain and require sanding between coats.
Pigments; Stain and Paint
Pigments are the costliest ingredient in paint. Besides providing color, pigments also impact paint's hiding power - its capability to cover a similar color with as few coats as is feasible. Titanium dioxide is the principal the 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 more easily.
Paint and Stain Additives
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 capacity to flow and level; they go on smoother than latex and dry more slowly, so brush streaks have more time to smooth out. That's why oil-based paints tend to drip on vertical areas more than latexes do.
Latex paint has been trying to catch up with oil-based paint over time. 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 induced 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 would have to let it to settle for a few hours. That is definitely no longer the situation with better paints, which is often opened and used right from the shaker without threat 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 temps from 50°F to 120°F. With added coalescents and, believe it or not, antifreeze, some latexes can be employed in the same temperature range, and even lower. Some outdoor latexes can be securely applied at heat as low as 35°F. Companies including Pratt & Lambert, Pittsburgh Paint, and Sherwin Williams have removed the surfactants to help their latex paints go on in lower heat. As the wetting agents have been removed, the latex dries faster.
UV blocking additives have been added to paints and stains to help slow the aging process. Sunlight is responsible for a lot of the breakdown of any covering. It fades colors, dries paint, and increases 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 greater reflection of the sun's rays.
If you live in a region with tons 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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