Probably not enough free moisture. The bowl is dried so a lot of free moisture from the mud cap or on the grapes would wick away into the structure. The grapes

Probably not enough free moisture. The bowl is dried so a lot of free moisture from the mud cap or on the grapes would wick away into the structure. The grapes have moisture but a lot would be trapped in cellular structures, they are not mashed as is done for wine, or exposed to the elements or still 'active' like they would be on the vine or in the sun.