My Honey Brown ale has been fermenting for 1 full week, I had great fermentation for appx 3 days. The fermentation has stopped and everything started to settle great. With the cool nights we had lately I noticed the carboy temp had dropped to the high 50 degrees. Last evening I decided to place a carboy wrap heater around the carboy to bring the temp back into range. When I got home today I noticed the temp in the carboy had climbed to 80 degrees. I immediately removed the heater. With the high temp change the beer started to ferment again. Did I ruin this batch of beer by raising the temp to the beer to the 80 degree mark.
Thanks
The good news is that you are probably not seeing a renewed fermentation. The high temp is most likely causing the CO2 to come out of solution. Some more good news. If the temperature swing would have happened during the first three days you would most likely dump the beer. Temperature swings stress the yeast. Stressed yeast can produce some unusually strong esters. The high temperature swing would most likely have caused fusel alcohols to be produced. Fusel alcohols are nasty tasting and will not age out.
Take a sample of the beer for a SG reading. Taste the sample to see what you have. Remember it is a very green beer without carbonation but should give you an idea of what the finished beer will be like.
Having your fermentor in a tub of water is the simplest way to prevent temperature swings. The temperature of the water can be adjusted up or down with ice filled bottles or a temperature controlled aquarium heater.
I hope the sample tastes rather decent.
I agree with @flars. Your fermentation was likely done. The first 3-4 days on an ale are the most important. If you can keep your temps in check for those days you have eliminated a large threat for off flavors.
