I live in an old house and I painted my kitchen light blue. After several years I noticed that there are strange white line-like patterns on the wall. They always run in right angles and seem to align with electrical wires behind the wall.
I am wondering, is it possible that somehow the electrical wires have caused the wall paint to pale? If so, what is the underlying mechanism? The only thing I am aware of is heat, since each imperfect conductor emits heat with passing current.
One other possibility would be an electro-magnetic field generated by the current interacting with iron particles in the paint, but I am not competent enough to tell if this is plausible.
The walls are made of brick and the wires are covered by plaster. I am not sure what kind of wiring is inside.