Hydrchromic Paint - mindsetsonline.co.uk
This amazing paint can either be used as-is or can be added to a binder. When painted onto a surface it appears semi opaque and then dries as a solid colour.
When water is added to the surface the paint turns totally transparent to reveal whatever is behind. When the surface dries; the paint changes back to a solid colour.
See http://www.mindsetsonline.co.uk/index... for more.