1.   However, they sometimes flex with use and can be damaged by abrasive cleaners.

2.   And for weathered finishes, there are abrasive cleaners and rubbing compounds.

3.   Do not use cleansing powders or abrasive cleaners.

4.   Frequent use of a window cleaner is recommended, and some authorities suggest occasional use of Bon Ami, a mildly abrasive cleaner, to remove film and wax.

5.   If an abrasive cleaner has been used often the surface may be rougher and more porous, so dirt will tend to penetrate and be harder to remove.

6.   We armed ourselves with butter knives and screwdrivers, steel-wool pads and abrasive cleaners.