Which mechanism leads to detachment of pietra dura inlay from Mughal-era sandstone?

💡 Explanation

Hygroscopic stress occurs when water reacts with soluble salts within porous sandstone; crystallization pressure exceeds the adhesive strength, because the sandstone expands more than the pietra dura, therefore the inlay spalls off, rather than remain adhered like metal expands or lichen erodes surface.

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