Crummy coping causes catastrophe
Keene's cement. A super hard plaster
is water resistant and scrubbable.
I am scrubbing this wall
as hard as I can wiyh a wet pot scrubber.
Not even a scratch.
Keene's cement can be used for shower finishes.
More about Keene's cement here...
Here I am scrubbing cheap drywall the same way.
I easily scrubbed off the acrylic paint, amd the paper is dissolving on the drywall.
A little more scrubbing, and I am through the gypsum core.