>>> I could see how cling film might have a 
>>> more-than-non-negligible
>>> effect on the air flow -- but when I think of a
>>> pack of biscuits sitting in a cupboard,

>> It is not the air flow, the cling film is keeping the 
>> moisture out that
>> makes the biscuits go soft.

> But isn't the moisture in the air? Isn't the moisture 
> flowing through
> the folds of the cling film just like the air is?

When I use or see cling film for food it is applied in a way 
to aim at air tightness - ie few or no holes of any great 
size. As a barrier to diffusion of water vapour it should be 
much more effective than air alone.


            Russell


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