Paint
From Principles of Applied Arts
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Contents |
Painting Techniques
History
Ancient painted walls, to be seen at Dendera, Egypt, although exposed for many ages to the open air, still possess a perfect brilliancy of color, as vivid as when painted, perhaps 2000 years ago. The Egyptians mixed their colors with some gummy substance, and applied them detached from each other without any blending or mixture. They appeared to have used six colors: white, black, blue, red, yellow, and green. They first covered the field entirely with white, upon which they traced the design in black, leaving out the lights of the ground color. They used minium for red, and generally of a dark tinge.
Pliny the Elder mentions some painted ceilings in his day in the town of Ardea, which had been executed at a date prior to the foundation of Rome. He expresses great surprise and admiration at their freshness, after the lapse of so many centuries.
Paint Composition
All paints are made up of three basic elements: colorants, binders, and solvents.
There are generally three components to a paint: binder, diluent and additives. However, only the binder is absolutely required. The binder is the part which eventually solidifies to form the dried paint film. The diluent serves to adjust the viscosity of the paint. It is volatile and does not become part of the paint film. Anything else is an additive. Typical binders include synthetic or natural resins such as acrylics, polyurethanes, polyesters, melamines, oils, or latex. Typical diluents include organic solvents such as alcohols, ketones, esters, glycol ethers, and the like. Water is a common diluent. Sometimes volatile low-molecular weight synthetic resins also serve as diluents. Typical additives include pigments, dyes, catalysts, thickeners, stabilizers, emulsifiers, texturizers, adhesion promoters, flatteners (de-glossing agents), and the like. After application, the paint solidifies and becomes tack-free. Depending on the type of binder, this hardening may be a result of curing (polymerization), evaporation, or even cooling. In oil-based paint, curing takes the form of oxidation, for example oxidation of linseed oil to form linoxin to create a varnish. Other common cured films are prepared from crosslinkers, such as polyurethane or melamine resins, reacted with acrylic polyester or polyurethane resins, often in the presence of a catalyst which serves to make the curing reaction proceed more quickly or under milder conditions. These cured-film paints can be either solvent-borne or waterborne. Other waterborne paints are emulsions of solid binders in water (in fact, such paints are often called simply "emulsions"). When the diluent evaporates, the molecules of the binder coalesce to form a solid film. Such emulsion paints are also known as latex paints because the polymer is formed through an emulsion polymerization through which the monomers are emulsified in a water-continuous phase. The polymer itself is not soluble in water and hence the paint is water resistant after it has dried. Residual surfactants in the paint as well as hydrolytic effects with some polymers cause the paint to remain susceptiable to softening and, over time, degradation by water. Still other films are formed by cooling of the binder. For example, encaustic or wax paints are liquid when warm, and harden upon cooling.
Colorants
Colorants are pigments used to create color, obtained from a variety of sources, organic and inorganic. Usually these are pre- dispersed UTC’s (Universal Tinting Compounds).
Pigment
- Main article: Pigment
Pigments, usually insoluble powders, are used both to provide color, and to make paint opaque, thus protecting the substrate from the harmful effects of ultraviolet light while also increasing a paint's hiding power.
Some pigments are toxic, such as those used in lead paint. Paint manufacturers replaced lead white with a less toxic substitute, which can even be used to color food titanium white (Titanium Dioxide) which was first used in paints in the 19th century. The titanium white used in most paints today is often coated with silicon or aluminum oxides for better durability.
Some newer paints - called prism paint - can produce effects where the color changes depending on the angle (orientation) at which it is viewed. Modern United States|U.S. and Canada|Canadian banknotes, specifically the newer higher denomination notes, have this effect on them. This effect is produced by having pigment molecules that are long and thin and are meant to dry in a specific orientation, with different ends of the molecule being different colors.
Binders
Another word to describe binders would be glue. The pigments themselves don’t stick to a surface. They are suspended in the binder and the dispersion sticks. Every binder has unique characteristics in relation to the film it creates when dry. For example: Linseed oil has an amber tone to it. On fine art oil paintings you can see this represented well. (Oil paintings have good color harmony because of the uniform film color).
Examples of binders include:
Linseed oil
Acrylic
polymer
Alkyd
Siccative oils, beer gluten, egg or milk protein, etc.... Siccative oil is oil that dries to a hard film; acrylic polymer resins can dry soft or hard, beer gluten is relatively weak, as are egg and milk protein binders. Weak binders reactivate when wetted, otherwise known as reversible. The best binders are those that behave as you expect them to.
Solvents
Solvents can sometimes be called thinners or vehicles. They evaporate after the paint has been applied. If you picture the individual components of paint, when the thinner evaporates, the color and binder are left on the wall, where you want them to be. The moisture is gone, hence, the paint has dried. Solvents can be slow drying or fast drying. Examples of solvents include water and turpentine.
A solvent is a liquid that dissolves a solid, liquid, or gaseous solute, resulting in a solution. The most common solvent in everyday life is water. The term organic solvent refers to most other solvents that are organic compounds and contain carbon atoms. Solvents usually have a low boiling point and evaporate easily or can be removed by distillation, thereby leaving the dissolved substance behind. Solvents should therefore not react chemically with the dissolved compounds — they have to be inert. Solvents can also be used to extract soluble compounds from a mixture, the most common example is the brewing of coffee or tea with hot water. Solvents are usually clear and colorless liquids and most of them have a characteristic odor. The concentration of a solution is the amount of compound that is dissolved in a certain volume of solvent. The solubility is the maximal amount of compound that is soluble in a certain volume of solvent at a specified temperature. Common uses for organic solvents are in dry cleaning (e.g. tetrachloroethylene), as paint thinners (e.g. toluene, turpentine), as nail polish removers and glue solvents (acetone, methyl acetate, ethyl acetate), in spot removers (e.g. hexane, petrol ether), in detergents (citrus terpenes), in perfumes (ethanol), and in chemical syntheses. isay
Solvents and solutes can be broadly classified into polar (hydrophilic) and non-polar (lipophilic). The polarity can be measured as the dielectric constant or the dipole moment of a compound. The polarity of a solvent determines what type of compounds it is able to dissolve and with what other solvents or liquid compounds it is miscible with. As a rule of thumb, polar solvents dissolve polar compounds best and non-polar solvents dissolve non-polar compounds best: "like dissolves like". Strongly polar compounds like inorganic salts (e.g. table salt) or sugars (e.g. sucrose) dissolve only in very polar solvents like water, while strongly non-polar compounds like oils or waxes dissolve only in very non-polar organic solvents like hexane. Similarly, water and hexane (or vinegar and salad oil) are not miscible with each other and will quickly separate into two layers even after being shaken well.
Driers
These increase the speed in which the binders dry.
Fillers
Fillers are added to paint by manufacturers to make it thicker at a less expensive cost. Fillers also add opacity to paints.
An example is whiting. Whiting is powdered chalk that can effect the translucency of paint. Some higher quality paint manufacturers don’t add fillers. A strictly labeled transluscent paint should have very little filler, or chalk.
To matte down the sheen of paint add Talc
Medium structure chart
You should study the different characteristics of binders and solvents to help you better understand where they should or shouldn’t be used. This chart is designed to show you examples and is not to be taken literally. Many other things are put into paint by manufacturers according to chemical recipes.
Artist Oil Paint + Linseed Oil Turpentine Acrylic Paint + Acrylic resin Water Gouache= + Gum Arabic Water Latex paint + Polymer resin Water Alkyd paint + Alkyd resin Mineral spirits Tempura + Egg protein Water *Fresco Painting + Lime plaster Water Casein paint + Milk protein water
- Fresco painting is unique because you don’t put binders in your paint. Wet lime plaster binds the pigments when it dries. Because there is no film left over the pigment it leaves the colors looking pure.
Paint store bases
When you go to the paint store and ask them to mix you a specific color, the person goes to the shelf and picks a can of untinted paint. He then puts the appropriate amounts of color into it, places the can into a mixer and viola! finished paint.
The reason why they do this is because it would be inefficient to stock premixed paint in all the colors they offer. In addition, this system gives them the power to change the color at will. As opposed to using only one clear base and adding color from there, it is cheaper to have paint bases the already possess whites in them for their pastel colors. This does pose some clarity issues when you are using paint to make a glaze. (See glazes)
All paint stores have a different system, but for the most part, they are the same systems with different names. This is one example of a paint base system used to make it easy for the manufacturer to efficiently mix colors into their paint.
Paint stores also have a computer color matching system that works with this base system to match any color they want. All you have to do is bring them a sample of the color you desire and the can match it almost perfectly, i.e. “shoot the color”.
Example: Paint Base System of Benjamin Moore Paints
1B = has chalks and fillers; very white, only achieves light colors
2B
3B
4B = little fillers – very translucent, achieves darker colors and costs more than the 1 base paint.
Note: Pigment and fillers affect opacity and coverage.
Note: What makes a good paint vs. a bad one?
Pure refined pigments.
Simple color formulas.
Pure, clear, strong binders
Don’t forget everyone has their opinions about certain brands; research all of them before you develop yours.
Painting on walls is a skilled craft that takes good technique and practice (see Base painting guidelines)
