PET plastic is amazingly resistent to oxidation and it is as available as your nearest trash can. Almost all soda, juice, etc are packed in this clear, brittle plastic with a very secure cap. FILL TO THE VERY RIM with either concentrates or mixed developer. Room temperature is fine. Tiny, 50ml liquor bottles (metal cap) are fine for smaller amounts and there are even tiny glass marbles (in case the larger ones do not fit) that are available in Arts and Crafts stores. - David Lyga