darkhorse said:
Actually Wayneb-I'd take your opinion too. 28 years of mead making's a pretty good qualifyer.
I just don't want to get into a big debate at this point.
Well, since I know that Oskaar sometimes works with an open top plastic primary as well as glass (as I do), he and I probably agree on the subject - so you might get some additional detail or a slightly different perspective from him, but I doubt you'll start a debate.

For primary fermentation, where the yeast are active enough to generate lots of CO2, an open topped plastic pail is fine as long as you keep it covered by something that prevents the introduction of airborne microbes, and keeps a reasonably stable buffer layer of that self-generated CO2 directly above the must. Personally, I use a dense weave towel over my bucket that has been soaked in sanitizing solution (I use Star-San for this purpose), and wrung out so that it is slightly damp but not dripping wet. I hold it in place across the bucket top by a ring of bungee cord that I got from a local sporting goods store. The cord conveniently stretches the towel tightly across the top, and keeps itself in place in-between the ridges that are molded into these food-grade plastic pails that are commonly sold as primary fermenters. I give a quick re-rinse to the towel in Star-San every time that I remove and replace it.
I've also used a large plastic garbage bag for the same purpose, after rinsing the inside of it thoroughly with sanitizer and I hold it in place with the same bungee arrangement that I use on the towel. I secure the plastic bag tight enough to prevent local air from freely circulating over the bucket top, but loose enough to allow a little escape path for the CO2 so it doesn't build up to the point that it pressurizes the bag.
Frankly, the towel works better than the bag, but I still use the bag when I want to start something and don't have any clean towels at hand. With three teen and pre-teen kids in the house, a shortage of clean towels is the case more often than I'd like! :tongue3:
Almost forgot -- be careful in the cleaning and sanitizing of the pail so that you don't scratch the inner surface. I have not had this happen to me, but other folks have reported that their batches have developed infections when they used scratched pails, and they've concluded that the deep scratches give pathogenic microbes a place to hide out from the sanitizer. Better safe than sorry -- I wouldn't recommend using a scratched pail.