How long does a street painting last?

Depending on location, weather and traffic, a street painting can be visible for many months after it has been completed – not clearly but faintly. Rain, moisture, wind and traffic will diminish its beauty very quickly, but typically it can be seen in a fairly good condition for a few weeks after its completion, if passer-byers respect it by not walking on it. I do find, however, a certain beauty in the way a street painting ages. It becomes a ghost of itself, fading like an old world fresco, mysteriously hinting at what once was.