[quote]mbg wrote:
I use a copper immersion chiller. Have use it for years and recently after reading about brewers using recirculating pumps (which I don’t have) to produce a mild whirlpool around the chiller I use a brewing spoon to stir the wort while chilling. This has cut my chilling times by more than half (almost two thirds). I see some repurpose an ice cream machine to do this.
Mike
Aren’t you concerned about having the lid off while cooling and the increased chance of contamination?[/quote]
Matt, You are correct that the lid will help keep contamination out. But, if you think about your whole process you might decide that you are better off cooling faster than keeping the lid on. Wort is more susceptable to contamination at 90-100 degrees than at 65-75 degrees. And, the faster you get the yeast pitched and taking off, the more that contaminating microbes will be crowded out.
I have decided that keeping the lid on while chilling is not important to me. I aerate by spinning a mix-stir with a drill, so I’m getting huge amounts of ambient air in the fermentor anyway. It seems pointless for me to worry about some additional exposure to air while chilling. I cool and pitch as quickly as I can and I find stirring and moving the imersion chiller around a lot cools much more quickly.
If you aerate with pure oxygen or use an aquarium pump with an inline filter, you might reducte the risk of infection somewhat by keeping the lid on while chilling. In my opinion, the slightly reduced risk of infection from leaving the lid on are far outweighed by the gains from fast cooling and using the room air to aerate. I think anyone who aerates by shaking, splashing, or spinning with a drill-driven implement is better off not worrying about keeping the lid on while chiling. And, the benfits of aeration with far outweigh the risk of chilling with the lid off.