All tombstones get dirty after a while and need to be washed to keep the appearance. If the stone is washed regularly it will stay fine for a long time. However, it is important to be careful when washing painted and gilded text and decor. After some time, painted and gilded text and décor becomes more and more fragile, so it is important not to be too hard to remove dirt that has settled in recesses in text and décor.
A polished surface lasts longer than a rough surface. This is because moss and lichen find it difficult to get an attachment on a polished surface. On a coarser surface it is easier for lichen and moss to start growing. However, a rough surface can withstand more heavy-handed washing, so it is usually good to wash these surfaces clean as well. On rough surfaces, you can use a scrub brush to remove dirt and vegetation.
Wash the tombstone with lukewarm water. Use a soft toothbrush. Be extra careful white wash of text and decor so you don’t accidentally scrape off color.