Paint - Application

Application

Paint can be applied as a solid, a gaseous suspension (aerosol) or a liquid. Techniques vary depending on the practical or artistic results desired.

As a solid (usually used in industrial and automotive applications), the paint is applied as a very fine powder, then baked at high temperature. This melts the powder and causes it to adhere to the surface. The reasons for doing this involve the chemistries of the paint, the surface itself, and perhaps even the chemistry of the substrate (the object being painted). This is called "powder coating" an object.

As a gas or as a gaseous suspension, the paint is suspended in solid or liquid form in a gas that is sprayed on an object. The paint sticks to the object. This is called "spray painting" an object. The reasons for doing this include:

• The application mechanism is air and thus no solid object touches the object being painted;
• The distribution of the paint is uniform, so there are no sharp lines;
• It is possible to deliver very small amounts of paint;
• A chemical (typically a solvent) can be sprayed along with the paint to dissolve together both the delivered paint and the chemicals on the surface of the object being painted;
• Some chemical reactions in paint involve the orientation of the paint molecules.

The application of the paint is fairly easily if done correctly. It is the prep work and order of operations that is tedious and detailed. Your first step when painting is to make sure you move all of the furniture, pictures, tables, etc. out of the room and most importantly out of your work space. Next is to lay down tarps or drop cloths to protect your flooring, but most of all if you spill or splash any paint. The next step, wall preparation, is a detailed process which could involve anything from skim coating, spackling, caulking, sanding, priming, taping, etc. After all the prep work has been completed you can now begin painting. Usually your first step in painting should be the "cutting in phase". This phase includes the brushwork around the edges, windows, doors, trim, molding, ceiling or wall line, etc. It is up to the painter of the order of wall spaces he or her chooses to do first. For instance it does not matter if you cut in the ceiling, or paint the window trim first and paint the walls last or vies versa. What is important is that the user cuts in first on every wall space. From there, depending of your order of operation, you can break out the rollers and being rolling the large open space on each wall space. After you applied the necessary amount of coats to the wall, you can remove any tape left behind and clean up. It is recommended that you do not try to wash your walls for at least two weeks after painting to let the paint cure fully.

In the liquid application, paint can be applied by direct application using brushes, paint rollers, blades, other instruments, or body parts such as fingers and thumbs.

Rollers generally have a handle that allows for different lengths of poles to be attached, allowing painting at different heights. Generally, roller application requires two coats for even color. A roller with a thicker nap is used to apply paint on uneven surfaces. Edges are often finished with an angled brush.

• Using the finish flat one would most likely use a 1/2" nap roller
• Using the finish eggshell one would most likely use a 3/8" nap roller
• Using the finish satin or pearl one would most likely use a 3/8" nap roller
• Using the finish semi-gloss or gloss one would most likely use a 3/16" nap roller

After liquid paint is applied, there is an interval during which it can be blended with additional painted regions (at the "wet edge") called "open time." The open time of an oil or alkyd-based emulsion paint can be extended by adding white spirit, similar glycols such as Dowanol (propylene glycol ether) or open time prolongers. This can also facilitate the mixing of different wet paint layers for aesthetic effect. Latex and acrylic emulsions require the use of drying retardants suitable for water-based coatings.

Paint application by spray is the most popular method in industry. In this, paint is atomized by the force of compressed air or by the action of high pressure compression of the paint itself, and the paint is turned into small droplets which travel to the article which is to be painted. Alternate methods are airless spray, hot spray, hot airless spray, and any of these with an electrostatic spray included. There are numerous electrostatic methods available.

Dipping used to be the norm for objects such as filing cabinets, but this has been replaced by high speed air turbine driven bells with electrostatic spray. Car bodies are primed using cathodic elephoretic primer, which is applied by charging the body depositing a layer of primer. The unchanged residue is rinsed off and the primer stoved.

Many paints tend to separate when stored, the heavier components settling to the bottom, and require mixing before use. Some paint outlets have machines for mixing the paint by shaking the can vigorously for a few minutes.

The opacity and the film thickness of paint may be measured using a drawdown card.

Water-based paints tend to be the easiest to clean up after use; the brushes and rollers can be cleaned with soap and water.

Proper disposal of left over paint is a challenge. Sometimes it can be recycled: Old paint may be usable for a primer coat or an intermediate coat, and paints of similar chemistry can be mixed to make a larger amount of a uniform color.

To dispose of paint it can be dried and disposed of in the domestic waste stream, provided that it contains no prohibited substances (see container). Disposal of liquid paint usually requires special handling and should be treated as hazardous waste, and disposed of according to local regulations.