A mushroom cloth is a specially selected piece of fabric whose abrasive properties are particularly useful for removing the outer layer (and soil) from edible mushrooms. The mushroom cloth is a generic term for any piece of clean fabric applied to the task of cleaning mushrooms. A mushroom cloth is preferred because mushrooms are porous and when cleaned under a running tap they absorb water, which affects their taste when cooked or served raw.
Mushroom cloth is used in bookbinding and the interior trim on cars.
References
Mushroom cloth Wikipedia(Text) CC BY-SA