Narrow-Bandwidth Television Association

Yes, x-rays, when not too weak, will go through aluminium, and especially if it is a thin foil. Why do you think that screening for x-rays is generally done by thick lead? The weight of the screening is what counts. And big and heavy atoms (especially lead) screen better than light atoms, e.g. Aluminium.

Ah yes. Thanks for jogging my poor memory! Basic schoolboy stuff I'd forgotten.

Steve A.