I think I remember reading somewhere here that accordion bottles infiltrate air(even though they dont leak liquids). Like most on APUG, I recycle drink bottles in 1 and 2 litre sizes. i also use pint and quart isopropyl alcohol and peroxide(brown) bottles, i even reuse the gallon jugs my deionized water comes in. Storing the contents in a dark cabinet suffices in place of dark containers.