There are a variety of materials with which gravestones can be made, but by far, the most used are granite and bronze. That is due to its durability and elegant appearance.
Whatever the selection of materials, the monuments in the graves should be tilted regularly to maximize their durability and keep the inscriptions as readable as possible. It is an amazing way to indicate that you are still thinking about the person who died.
For granite, due to its durability, the grave will not be damaged with a reliable cleaning. Some people may distrust using too much force and cause damage, but that is almost impossible with granite.
With a massive tool, it is recommended to use a non-metallic cleaning plate, as well as the use of detergent or non-ionic soap mixed with water. That will eliminate calcium deposits, which tend to accumulate on polished granite gravestones as a result of contact with rain and snow.
Turning to the bronze gravestones, these are a bit more complicated to clean. The reason is that they are usually made not only of bronze but also of one or two other materials, which are commonly used as a base.
Bronze plates are made of copper and tin, with small additions of zinc and lead. They have a varnish applied to seal their original appearance, but will gradually deteriorate over time.
Therefore, the use of specialized wax is necessary to keep a bronze gravestone in good condition. That is easy to use enough and only requires you to rub it freely at regular intervals, maybe every 3-6 months.
Since these bronze monuments are generally flat above the grass level, they are more prone to fall and water stagnation. The granite base can be cleaned using the same aggressive cleaning method used in granite gravestones.