tile grout mixed with iron oxides
it’s near impossible to clean away the excess without staining. I do my best. some of the the tile gaps I’ve filled with newman clay and barnard clay instead of tile grout. they all crack as they dry
I try to repair the cracks by pouring a layer of clay slip over the entire surface. something you are taught never to do in ceramics:
if a large crack appears, you should always wedge the entire form back into plastic clay and start again from scratch
if you smooth it over, it will likely reappear again once water escapes from the body
