You should be fine in plastic for a month or two. Glass is for long term storage (3 months or more) and mainly a concern for wine makers. Plastic is permeable which simply means it allows air in. BUT this is a very slow process and would probably take many long months to affect your brew. There are also now non-permeable plastic carboys on the market.
"S. Parker McCullock" <elonnc@yahoo.com> wrote in message news:vl16nci5afn0d7@corp.supernews.com...
Have just brewed my 8th batch of home brew and thought I would try something different, but not sure if I have done the right thing or not and wanted to get some opinions. In the past I have been doing single stage fermentation in a plastic carboy. The fermentation process goes strong for about 7 days and then slows down to about a bubble every two minutes coming out of the air lock. This time, when it slowed down, I transferred by siphoning the beer into another plastic carboy but I didn't transfer the sediment at the bottom of the first one. Basically I started a secondary fermentation process. My concern is that all of the readings that I have read say that this should be done in a glass carboy. Now I am concerned I may have messed by batch up. The second fermentation process appears to be fermenting ok, I am seeing a consistent release of gas through the airlock, not as fast as the first stage but noticeable none the less. What's the deal with the glass carboy for the second stage fermentation?