What's too cold

We made a German Pilsner (all grain) and it's in its first fermenter.  The directions recommended a temperature of 64-72.  We moved it into a room where there are no vents for the heater and the last time I checked, it said it was 61 degrees.  Is that too cold? Otherwise it will be in a room that is around 72. I heard that cold was better for pilsners, but wanted to make sure.  Thanks.

---Robin

As long as there is yeast activity then it's not too cold.  Keep in mind that the yeast produces heat. Enough that the fermenting brew will be at least two degrees warmer than the room. I've seen the fermometer that I have stuck to the side of the carboy read six degrees warmer than the thermometer on the wall right next to it. I aim for the mid 50s when making lager, which means I keep my basement closer to 50. I like to make it on the low side of the temperature range.

I ferment lagers at 54, dicetyl rest at 62, and lager at 37 for four weeks. I do the first week of lager in the fermentor and on the 7th day I rack to a keg and filter. Then two weeks at 37 in a keg adapted with an airlock and the final week seal the keg and force carbonate it. I developed this by trial and error and it work for me with my equipment. I use chest freezers controlled by Ranco digital controllers and my lager freezer has a CO2 line run into it. I believe the most critical part of a lager is the temperature control.