Never leave painting panels wrapped in bubble wrap or foam for long periods of time. Both have a detrimental effect on painting panels causing the whole package to sweat without any air flow.
This can cause bubbles to appear under the surface of gesso primed painting panels on aluminium. This is the result of the moisture permeating the gesso surface and hitting the impermeable aluminium. The moisture will travel along the aluminium and collect creating small bubbles of moisture that will extrude through the gesso layer and pit the aluminium.
Both the gesso and aluminium panel will have to be sanded back to the original aluminium.
Gesso is a permeable surface until it has been sealed with paint.
We only recommend using bubble warp and foam to transport paintings from A to B and not as a long term packaging solution.