I regularly use glass marbles in clear, plastic juice containers to displace the empty air space (with either BW or color developer) and the result is literally indefinite preservation of developer (as long as the solution is fully up to the rim of the container). These bottles are really airtight (like glass) but I am wondering if, in this high tech age with miracle plastics, there are lighter 'solutions'. Plastic packing peanuts I fear are not fully impervious to chemical saturation. Do you know if this is true or do you know if there are other, even 'creative' ways for such physical displacement? I already know about the method of spraying anti-oxydent and do not wish to employ that method. The marbles work great but the bottle becomes quite heavy when full of marbles. (For really small quantities I use tiny 50ml liquour bottles that I find sometimes on the streets.) Thank you for any info you can impart. - David Lyga.