How we clean concrete depends on the purpose of the cleaning and the extent of the work to be done. A careful diagnosis of the problem is essential for choosing an effective and successful cleaning method. Usually there is more than one way to do the job, and each one has its pluses and minuses. Water and chemical cleaners can lead to problems caused by excessive moisture or unanticipated chemical reactions. Abrasive blasting and flame cleaning will change the surface texture and appearance; power tools can damage thin sections or remove more concrete than is desirable. When selecting a cleaning method, make trials, starting with the gentlest method that will be least damaging to the concrete or hazardous to workers. Work up other harsher methods, using then only when the gentler measures fail. One suggested sequence of test approaches for removal of dirt, stains, and efflorescence is: 1. Dry scrubbing with a stiff fiber brush 2. Wetting down the surface, scrubbing with a stiff fiber brush, followed by low-pressure washing 3. Steam cleaning or high-pressure washing 4. Chemical cleaning compounds 5. Abrasive blasting, either wet or dry 6. Flame cleaning