When we were teen-agers we worked part time at our father's car lot. We detailed the cars and did minor motor repairs. One of our favorite tools was a steam cleaner that ran on diesel fuel. Given enough commercial strength detergent, it could clean most anything with its forceful spray. We cleaned undercarriages, motors, transmissions and grease-ridden nuts and bolts. They all shined like new. Unfortunately, steam cleaners in those days had a tendency to explode, and we thus were in constant fear of being burned, blinded or otherwise maimed.

That was in the '60s, long before anyone realized that new technology one day would produce the pressure washer. Did you ever drive into one of those do-it-yourself car washes where you put several quarters into a box and get a high-pressure spray mixed with detergent followed by a clear-water spray? That was one of our first experiences with a device that 25 years later would become a tool as common to construction as a hammer or saw.

A pressure washer is a machine that mixes water from a garden hose with air from a compressor to form a fine, high-pressure spray of water capable of cleaning just about anything. The water is sent from the machine to a cleaning wand via a high-pressure hose. At the end of the wand is a removable tip. Each tip is designed to create a different spray pattern. Many things can be cleaned with a pressure washer: Windows and their frames. Your driveway and front walk. Any concrete anywhere, horizontal or vertical. Your car, its tires, the motor or transmission. Your garden tools and wheelbarrow. Your barbecue, a basketball, even dirty sneakers.

In the early phase, there was one size only....big. And, they were priced out of most folks' reach and were mostly used commercially by painters for removing paint.

Pressure washers are powerful. Once we were chatting with one of our crewman who was preparing a house for paint using a heavy-duty pressure washer. He turned to respond to our question and in the few seconds that it took him to answer he inadvertently cut a hole in a piece of redwood plywood siding.

Since then there have been major advances in pressure washers. Today, one can find them in every size and shape. Smaller units range in price from $200 to $500. Larger ones go for as much as $2,000. Truck-mounted industrial models sell for tens of thousands of dollars.

There are two values that are used to measure the power of a pressure washer - air pressure and water flow. Air pressure is generated by an onboard compressor and is measured in pounds per square inch (PSI). Water is provided by a garden hose and its rate of flow is measured in gallons per minute (GPM). To find out how powerful a pressure washer is, simply multiply its PSI rating times it GPM rating. For example, 1,000psi x 1.2gpm = 1,200 - a very low power rating. Another example, 3,000psi x 6gpm = 18,000 - a high one. A power rating of 1,200 is great for washing cars and other light cleaning jobs. A machine with a rating of 18,000 does it all, from cleaning motors to removing paint to washing window screens.

A couple of nice things about a pressure washer are that it doesn't use much water and only a very small amount of electricity. It is reasonably safe as compared to a steam cleaner or a sand blaster, and except for losing a removable spray tip now and then, the pressure washer is a dependable and low-maintenance product.

Before you go shopping for a pressure washer there are a couple of special features you should know about. Better pressure washers have an injection port that can be used to draw in a liquid detergent or pesticide, or any liquid for that matter. You can use your pressure washer to spray your apple tree for moths and then use the same machine to wash the chemical overspray off your neighbor's car. Some larger machines have a pressure adjustment. You can regulate the amount of pressure and therefore easily control the force of the water at the tip of the machine. When a machine doesn't have a pressure regulator, you are forced to vary the distance between the tip and the surface being cleaned to regulate the force.

Finally, be sure to check out the interesting array of tips that are available. There is one that pulsates thereby using less water and power. You can even purchase a window-washing accessory.

We don't like to use chemicals to control insects in our yard. As a result our home gets covered with spider webs every year. Using a pressure washer we completelyl clean our home's exterior in just a few hours. And, there isn't a better tool for cleaning window screens and patio furniture.

Before you buy, rent one. You'll be hooked after one try.