Funny story, but I can't verify it:
I was doing some work in a boutique hotel in the Lakes last winter and they had big mirrors installed in all the bathrooms there. The guys who were installing them told me that they had just finished a really good job in Manchester in a large hotel where the mirrors had all been installed using cheap-as-chips silicone. They were called in to replace over 80 mirrors.
The numpties who installed the mirrors in Manchester thought they would have a "bit of a larf" and decorate the bare walls with large phalluses and swear words, all drawn in copious amounts of silicone to which the mirrors were then fixed.
Unfortunately, the cheap silicone then started to corroded the silver backing on the mirrors and all the hidden creativity started to show through in all 80 rooms at pretty much the same time!