On Mon, 6 Mar 2017 23:41:27 -0800 (PST)
whit3rd wrote:

The traditional solution is chalking. Some paints are intended to
let loose of the top layer of pigment in normal weathering, which
exposes a clean surface underneath, so to speak. Application

the etfe material they are using is water loving

spray on water and anything on the surface comes off

any surface that had this would be easily cleaned without
mechanical washing and no other surfactants are needed to clean