1. PRESSURE. Anyone that has ever used a paint scraper to scrape old paint off a concrete floor knows the amount of "pressure" required to remove old paint. A pressure washer with the right tip can make the job much easier and requires much less elbow grease. A pressure washer in the 3,000 - 4,000 psi range should do the trick. Avoid 0° nozzles and opt for a "fan" tip which will spread the pressure out over a greater area. These tips will help lift off the paint without pitting out the concrete surface or causing the "snail trails" caused by 0° tips.
2. HEAT. Pressure washing with hot water is essential for paint removal. Industrial pressure washers are capable of generating hot water and steam up to 330°F. Cleaning just about anything is easier with heat, and paint is no exception. As old, dried paint starts to heat up, it physically changes as the chemical bonds holding it together begin to breakdown. Heat makes paint expand and loosen up, which makes it easier to remove with PRESSURE.
It may be possible to remove paint without each item in this trifecta, but where you lack in one element you will need to increase another. For instance, many homeowners don't have the luxury of a hot-water pressure washer so they will need to use more (expensive) chemicals to achieve better results. Increasing the pressure too much may lead to costly damage and should be avoided. If in doubt, consider hiring a local, professional power washing service to complete your paint removal project. Just verify that they are using PRESSURE, HEAT, and CHEMICALS!
ACME Powerwash is a mobile pressure washing company serving residents and businesses in the Phoenix Metro area and all of Central Arizona. Visit them online at http://www.acmepowerwash.com for more information about power washing services.