Washing dishes is not the most rewarding task. Cooking can be creative, but cleaning up afterward seems like a waste of time and leaves the person washing complaining about "dishpan hands." The development of the dishwasher has helped relieve some of the monotony, as well as the grease and grime. It operates on a simple principle of washing dishes that have been placed on racks inside the machine with multiple jets of water. The modern dishwasher has features that cater to fine glassware or the toughest pots and pans; multiple cycles that clean, sanitize, and dry; and under-the-counter or stand-alone models for every size, use, and price range. It is far from perfect; tough foods may need personal attention before and after dishes and pans are cleaned in the dishwasher, and few owners of crystal glassware and fine china are willing to trust them to a machine. But the dishwasher, like other kitchen appliances invented and improved in the twentieth century, is a fixture in many kitchens of the twenty-first century.
The major obstacle to washing dishes has always been the availability of water. Early civilizations used limited numbers and types of dishes, utensils, and cookware and carried them to streams, ponds, or troughs of water for cleaning. The second choice was to carry the water to the dishes. Women carried water in buckets from communal water sources or from private pumps behind their homes or apartment buildings into the early twentieth century, when indoor plumbing finally brought water indoors, not only for bathing but for kitchen use as well.
The first dishwashers were patented in about 1850, but, like machines for washing clothes, they were large contraptions that used steam power and supplies of heated water to soak many dishes at a time. In some models, the dishes were held on cradles that rocked through the water; others had paddles that sloshed water around the dishes or circular racks that held the dishes and rotated to circulate them through the water. An assortment of propellers, plunging casings bearing the dishes, and plungers that drove water over the dishes were incorporated in other machines. In 1875, C. E. Hope-Vere created a machine that directed sprays of water toward racked dishes; the idea of the water jets was adopted by other inventors including A. W. Bodell, whose model was introduced in 1906. Another, the Blick machine, used a propeller that sprayed jets of water over racks filled with dishes. This basic idea is the one used today.
The first publicly displayed models were introduced in about 1915, but the dishwasher was not widely manufactured and sold to private families until about 1930. The dishwasher was not an immediate hit. The refrigerator was introduced at about the same time and swept America; but this is logical because food preservation is far more important than dishwashing. The machines were also too inefficient to completely eliminate hand work; to be fair, this was not entirely the fault of the dishwashers—soaps of the day were not suited to the task. By the 1950s, special dish-washing soaps that clean without sudsing and rinse away began to be developed especially for dishwashers, and the public began to demonstrate more interest. The automatic dishwasher is still not an absolute in every kitchen, but, by the 1970s when more women
The major components of a dishwasher are made of steel and plastic. The basic structure consists of a steel frame assembly and a steel door panel. Sheets of stainless steel are purchased and fabricated in the required pieces and shapes in the factory; both the door and the wrap-around cabinet for standalone models are purchased as coiled sheet steel that has been prefinished in several standard colors. Other small steel parts are designed in house but made by suppliers to the manufacturer's specifications.
The racks that hold the dishes are also made of steel, but it is delivered to the factory as coiled wire. To coat the rack tines to prevent them from scratching dishes, the racks are dipped in plastic in the form of powder polyvinyl chloride (PVC) or nylon.
The inner box that holds the racks and the washer arms is called the tub. It is a single piece (not counting the piece lining the inside of the door) that is injection-molded in the plant. The injection molding is done with pellets of calcium-reinforced poly-propylene plastic. This plastic is respected for its strength and for the fact that it is inert; that is, it won't react with chemicals like those in detergents and is resistant to water and heat. Many other parts including the basket for cutlery, containers for detergent, and the wash tower and spray arms are also injection molded.
Motors, pumps, and electrical controls and components are made by subcontractors in accordance with designs by the dishwasher manufacturer.
The engineers who design dishwashers are interested in improving two key features of their products. Efficient cleaning is, of course, the biggest marketing feature, but consumers are also interested in quiet operations. Cleaning systems consist of a wash tower and sprayer arms, but the openings, the power of the water pump, and positions of racks relative to the washers are all design elements. In the late 1990s, consumers became increasingly interested in the dish-washer as a tool for sanitizing dishes, so design efforts have been aimed at adding heating methods for killing germs.
Manufacturers have taken different approaches to keeping their dishwashers as quiet as possible. Maytag, for example, uses a single, powerful motor for all operations and wraps the outside of its machines with heavy insulation. By contrast, Amana Appliances has equipped its dishwashers with two motors (one to operate the water pump and another for the drainage system). Together, the two motors have the same horse-power as single-motor units, but less insulation is needed for quiet operation.
Design of the exterior of a stand-alone model is somewhat more sophisticated because it has to have an attractive outer cabinet. Usually the top of the stand-alone dishwasher is a wooden cabinet top so the machine will function as a spare work surface.
Quality control is assured by three basic processes. First, the assembly line workers are trained in quality issues and can reject parts or partially assembled machines. Second, the assembly process is overseen by line supervisors; when assembly is complete, quality engineers inspect the finished machine and test selected units. The most important part of the quality control process may be a design step that Amana Appliances calls a failure mode effects and analysis (FMEA). As soon as problems are observed during assembly or are reported by customers through the warranty process, corrective steps are taken. The analysis is a highly regimented learning process that continuously cycles improvements, customer feedback, and corrective actions through the marketing and design process so new models and lines benefit from any changes to the old.
Dishwasher manufacturers produce a range of lines of dishwashers and other appliances but no true byproducts. Waste is virtually eliminated by a thorough recycling program that includes metals, plastics, and paper.
All industries struggle with the issue of how to attract more customers to their product. For dishwashers, the market is still growing because it is a more open field than for other appliances. Marketers discuss this in terms of market penetration; for example, 99.8% of American households own refrigerators, but only 56.5% have dishwashers. This seems promising for dishwasher manufacturers, but it shows that potential customers who don't have dishwashers may not see that these appliances provide benefits over hand-washing dishes. To attract customers, the latest advance in dishwasher manufacture is the sanitization option with a high heat cycle to kill bacteria. Quiet operation, energy efficiency, and clean dishes without prerinsing are existing features that are continuously being improved.
Cohen, Daniel. The Last Hundred Years: Household Technology. New York: M. Evans and Company, Inc., 1982.
Weaver, Rebecca, and Rodney Dale. Machines in the Home. New York: Oxford University Press, Inc., 1992.
Amana Appliances. http://www.amana.com (August 2000).
— Gillian S. Holmes