Oil or Latex Paint?

by admin on January 27, 2013



Latex Paint vs. Oil Base Paint

Paint refers to a colored, pliable substance in liquid form that transforms into a solid film when applied to a surface. Paint serves to decorate, protect or add texture. Cave paintings discovered in many locations around the world indicate that prehistoric man developed and used paint over 40,000 years ago. Charcoal, hematite, manganese oxide and ochre supplied the pigments for these early cave wall decorations. Amazingly, paintings created by ancient Egyptians retain bright coloration after 2,000 years. The culture mixed a sticky component with egg yolks and pigments derived from plants, sand or soil, which created a palette consisting of six basic colors.

Pigment and binders comprise the primary ingredients found in paint. Binders from the solidified film and components of modern day binders consist of acrylics, alkyds, vinyl/acrylics or vinyl acetate/ethylene. Some brands also use epoxy, melamine resins, oils or polyesters and polyurethanes. These adhesive ingredients may exhibit varied properties from durability and flexibility to a particular finish.

Oil Based Paint

Caves found in Afghanistan contain the earliest known examples of oil based paint. Created sometime around 650 A.D., researchers discovered that the paint consisted of poppy seed and walnut oils. European cultures applied oil based paint as decoration during the 12th century. However, artists did not widely use the medium until the 15th century because documentation reveals that in addition to having an extended drying time, the oil base also affected the finished color of the artwork.

Linseed oil served as the base and binder of modern paints, which remain in use today. Thinning or cleaning equipment used with oil paints requires using mineral spirits or turpentine. Oil based paints contained petrochemical derivative solvents that carried the binders and pigments of the product. During the drying process, the solvent evaporated, leaving behind the solidified pigmented binder. Before the invention of latex paints, flammable, lead-filled, toxic oil paints were the only medium available for finishing surfaces on building exteriors and interiors.

The oil paint manufactured today does not have the same thickness compared to versions made decades ago. Formulas changed to comply with environmentally friendly requirements. If containing high levels of solvent, the paint must bear a “quick dry enamel,” “industrial maintenance coating” or “marine paint” label. The increased expense also makes the product hard to find in gallon increments. The advantage of the newer formulas includes quicker application.

Latex Based Paint

Emulsions commonly referred to as latex paint consist of water and minute polymer particles. Acrylic, styrene acrylic or vinyl acrylic comprise the binders. Latex paints cure when the water and any other solvent evaporate, which fuses the binding polymer particles. The paint also contains a combination of granulated fillers and pigments. The fillers typically provide durability and texture and consist of any number of cheap materials that include diatomaceous earth, lime or talc. The ratio of ingredients differs depending on the designated use or the manufacturing brand. Some latex paint contains liquefied dyes for coloration.

Paints found on the market today feature natural or synthetic pigments. Natural pigments come from calcium carbonate, clay, mica, silica or talc. Manufacturers use engineered molecules in blanc fixe, calcined clay, calcium carbonate or pyrogenic silicas. Hidden pigments consisting of iron oxide, phthalo blue or titanium oxide not only color the paint but additionally provide a protective barrier against ultraviolet radiation.

Paint additionally contains various additives included in small quantities that produce a specific effect. Additives serve as adhesion agents, catalysts, emusifiers, stabilizers and thickeners. The ingredient might also alter the finished appearance, enhance flow, change surface tension or protect against weathering.

Differences between Oil and Latex

Besides base ingredients, oil and latex paints vary during curing. Even when dry, moisture resistant oil paints continue reacting with oxygen, which causes cracking and peeling in time. Latex dries thoroughly in two weeks, but remains flexible. Moisture and oxygen buried beneath the paint easily pass through the surface and evaporate. Latex also expands and shrinks with temperature changes, which adds to the product’s durability. Oil paints bind with irregular surfaces more easily as the oil penetrates porous surfaces like wood. The paint also permeates cracks or pores of previously painted areas.

The differences in each type of paint also require surface preparation before applying one on top of the other. When applying latex over oil paint, prepare the surface by sanding with 100 grit sandpaper or the latex will not bind to the smooth, often glossy surface. On exterior surfaces, applying latex over oil paint creates more problems. Constant temperature changes cause contraction and expansion in the latex. The underlying oil coating suffers drying and cracking, which creates peeling sooner. Interior surfaces do not suffer this dilemma. When painting exterior surfaces previously coated with oil paint, either apply oil paint or remove the paint, prime and seal the wood then paint with latex.

Which is Better: Oil or Latex?

Latex based paints readily accommodate every surface from small indoor projects to expansive exteriors and interiors of industrial buildings. Many prefer latex due to the product’s smooth application, quick drying time and the ease of soap and water clean-up. Latex remains less toxic and does not require ventilation during indoor application. Consumers find that when shopping for paint, latex brands have many more color options. Latex also comes in finishes that range from matte to high gloss.

Many painters prefer applying oil based products over surfaces previously coated with oil paint. Especially on exterior surfaces, this technique saves preparation time. On bathroom baseboards and other high traffic areas, oil paints resist staining and offer a higher degree of durability. However, unlike many brands of latex paint, oil based versions do not resist mold and mildew. Oil also remains the best choice for any type of exterior metal work, particularly on dirty or rusty areas. This type of paint additionally better withstands colder temperatures. The fumes, drying time and extensive clean-up measures required largely make oil paints impractical. Various locations throughout the country also ban the use of oil base products secondary to the toxic ingredients that harm the environment.

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