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 between raging blizzards to innocent looking sunlight on a bath room wall. The full total thickness of the paint that eventually ends up on the exterior of your residence is usually about one tenth the thickness of your skin, and interior paint is even thinner. We ask a great deal of that covering of skin. What it can do depends on a variety of factors, like the quality and brand of paint or stain, and how well the surfaces 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 coat should resist fading, peeling, or yellowing, and also be easy to maintain, free from impurities or waxes which could collect dirty residue and make cleaning or recoating difficult. External paints should dry with a toughness that resists deterioration from all sorts of exposure, and an elasticity which 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 exterior should give a similar high performance.
Historical Development of Paint and Stain
The oldest known paint was utilized by the painters of Lascaux, who ground natural pigments with water and a binder that might have been honey, starch, or gum. You might be wondering why these cave paintings have lasted thousands of years while the paint on the south part 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 house, 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 mixed with Earth and plant dyes to paint images which have lasted a large number of years. The Egyptians used asphalt and pitch to protect 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 advanced varnishes such as, shellac, turpentine, copal, and mastic. The formulas and applications for those varnishes also evolved little in the following 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 flat and hard, and can be tinted with other pigments. Like stains, milk paint must be covered with a wax or varnish, and it is very durable.
Created from hogs' bristles, badger and goat hair, brushes also evolved 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, are still a preferred brush for oil-based paints.
Pigments originally came from anything that bore a color, from ground up Egyptian mummies to road mud. Most mineral or inorganic pigments came from rust, potassium, sea salt, sulphur, alum (aluminum), and gypsum, among others. Some extravagant projects incorporated precious stones such as lapis lazuli. A huge selection of organic pigments from plants, insects, and animals constructed 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 shared in 1773 was reprinted 14 times until 1900, with only small revisions. However, the colder climates of northern Europe did bring 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 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 blended on site, in which a ground pigment was blended with lead, oil, and solvents over sustained high temperature. The maladies that arose from harmful exposure were common among painters at least before late 1800s, when paint companies started out to batch ready mixed coatings. While contact with toxins given off during the mixing process subsided, contact with the harmful elements 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 find a replacement for the natural pigments and dyes that came from Germany. They commenced to synthesize dyes. Today many pigments and dyes are chemically synthesized.
Innovations 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 altered 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 new category of paints and stains known as "water borne." Created by the need to comply with stricter regulations, water borne coatings decrease the volatile organic substances, or VOCs, within standard paint and stains. Dangerous and flammable, VOCs evaporate as a coating's solvent dries. They could be inhaled or soaked up through the skin, and create ozone pollution when exposed to sunlight.
PAINTS AND STAINS... THEIR CHEMISTRY Paints and stains contain four basic types of ingredients: solvents, binders, pigments, and additives.
Paint and Stain 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 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 toughness. The expense of paint depends in large part upon the grade of its binder.
Because water is the vehicle in latex paint, it dries quickly, enabling recoating the same day. The odor that you see when by 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 include a greater amount of acrylic resins for increased hardness and durability.
Alkyds and oil-based paints are simply the same thing. The word alkyd comes from "alcid," a combination 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 high performance combinations such as two part polyester-epoxy for professional use and a urethane improved alkyd for home use. Urethane boosts sturdiness.
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 raise hardwood grain and require sanding between coats.
Pigments
Pigments will be the costliest element in paint. In addition to providing color, pigments also affect paint's hiding power - its ability to protect an identical 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.
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 stridations have a chance to level out. That's why oil-based paints tend to run on vertical surfaces 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 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 let it to settle for a couple of hours. This really is no longer the situation with better paints, which is often opened up and used right from 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 stick and dry in conditions 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 outside latexes can be safely applied at temperatures at only 35°F. Companies including Pratt & Lambert, Pittsburgh Paint, and Sherwin Williams have removed the surfactants to help their latex paints be applied in lower conditions. Because the wetting agents have been removed, the latex dries faster.
UV blocking additives have been put into paints and stains to help slow deterioration. Sunlight is accountable for a lot of the breakdown 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 contain finely ground metals and ground glass which is now being added for even greater reflection of the sun's rays.
If you stay in an area with plenty of humidity, rainfall, 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.
Sound Quality Painting
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Lake Stevens WA 98258
(425) 512-7400
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