I have a concrete (stone) vertical wall. I want to put a picture on it.
I have several limitations:
- I want to make it in a security, so I want to place something on the wall, that would be transparent or very similar to the original color.
- I am not a scientist and have no access to industrial materials, so want to make it out with everyday materials.
The wall itself has properties:
- It looks on the south, so sun lights on it almost full day (as a consequence, it is certain temperature and low humidity)
- Overall direction is vertical; while it is not fully straight, it has relief.
- There is little overhand above the wall, so it would not get heavy water stream in case of straight rain
So I did think about colored bacteria or mold (or other unicellular), that i can put on the wall with nutrients, but in case of mold it requires warm but wet environment. In the case of bacteria, I have no enough expertise to figure out which are needed and how to make them grow.
So maybe there is some chemical reactives that I can put on the wall, and under sunlight it would become colored in some time. Or something that becomes colored after becoming wet after rain?