As a side note: Some PET bottles are not straight PET. Coca Cola for example is using plastic bottles made from a co-extrusion or co-injection process, which contain up to 7 layers of different polymers, aiming to stop gas permeability and maintain the 'fizz' over a long time. The tiny bottles are later heated and blow-molded into their final shape. However, I don't know how resistant Coke bottles are to darkroom chemicals compared to the typically used polyethylene bottles. If I remember correctly, Coca Cola had a patent for this process, and it is now used to mold automotive plastic fuel tanks. Regards Ralph W. Lambrecht http://www.darkroomagic.com On 2005-11-29 19:58, "John Black" <jblack@xxxxxxxxx> wrote: > Some plastics are indeed quite gas permeable. I don't know which are the > best but PETG seems to be almost as good as glass. Glass is however cheap, > plentiful and reusable. I use glass and shall continue to do so. ============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.