items at once quickly and efficiently; 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. Expression In the liquid application, paint can be applied by direct application using brushes, paint rollers, blades, scrapers, 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 an 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. Depending on the quality and type of liquid paint used, the open time will vary. Oil paints for instance are renowned for their open time as oil paints allow for artists to blend the colors for extended periods of time without having to add any extending agents. Paint application by spray is the most popular method in industry. In this, paint is aerosolized 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 that travel to the article 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,