when do I cool to fermenting temp?

I am an extract brewer and I have been struggling with an unknown off flavor lately, kind of bitter/astringent and it has me rather discouraged. As a result, I have been examining my procedure looking for things that may need improvement. I shared some at a recent brewclub meeting and they were unable to difiniatevely determine the source of the problem. Some speculations were that it may be a mild infection/contaminated yeast. I used rehydrated Nottingham for all of the batches with the problem. I am thinking that if it is a contamination/yeast problem the first action would be to quit using nottingham. The other thing I am considering is maybe my lag time is too long (usually about 48 hours). I am thinking that I can decrease my lag time by waiting to chill the beer to fermentation temp. I currently ferment in a glass carboy with blowoff tube in a swamp cooler. My pitching temp is 68-70 degrees, and my fermentation temp in the swamp cooler is 65-60 degrees. I pitch my yeast and then immediately place in the swamp cooler. My question is should I wait until I see visible signs of fermentation before I place it in the cooler? It seems as this would decrease lag time, but I am afraid of off flavors from warm fermentation. What should I do?

As far as temp is concerned I would want to get the beer down to fermentation temp before pitching the yeast - you are right to worry about off flavors from a heightened temp. That said, though, I do not think your lag time is the problem - 48 hours is not unusual and it would be hard for an infection to get going so quickly that it took over. Also, I do not associate bitter/astringency with wild yeast or bacteria.

Are you steeping any specialty grains? If so, what temps are you steeping them at? Bitter/astringency sounds like tannins and those can come from steeping your grains at too high a temperature.

yes i am steeping grains and that was the first thing i addressed. I was using a cheap thermometer, and thought that could be the problem. I have since got a trustworthy digital thermomemeter and steep at 162+/-. I do have very hard water, i havent checked the ph yet but I understand that high steeping temp/acidic water could leech tannins. fixing the steeping temp did not seem to fix it. Also, it seems like the off flavor subsides some with time. I am perplexed by this as all of the reading i have done indicates that neither a contamination problem or a tannin problem should subside.

Ph could be the issue. 162F seems like a fine steeping temp. Tannins will drop out of solution, I believe (???). I wonder if you are just tasting young beer that hasn't had time to completely come together?

If you do want to shorten your lag time, you need to aerate better before you pitch. The more O2 you get in the wort before pitching, the shorter your lag time will be. Especially since dry yeast already has a good cell count going for it. Also, rehydrating the yeast before pitching will help that as well.

JLem makes some good points. Another thing to look at is how long you have the beer in primary. As the beer ferements, the yeast will give off byproducts that can give you off flavors. After fermentation is complete, the yeast will then break down some of those byproducts. If you bottle too soon, you can interrupt this process and then it takes longer for the yeast in the bottle to do it.

I dont think it is just green beer because the taste is so strong. I think I have a decent feel for green beer taste and this off flavor I am trying to describe is very strong to the point of overpowering the beer. it seems to take months in the bottle to get to the point where it is drinkable. I stopped aerating a while back because I read on Danstar's website that it is not necessary to aerate dry yeast. I will start doing it again though. As far as bottling, I dont use a secondary anymore for most beers, so it spends about 2 weeks in the primary before bottling. If it is tannins and the cause is a combination of temp and ph, could I lower the steeping temp to offset the ph problem?

Try another week in primary. Bulk aging seems to work faster than bottle aging, so extra time in the primary will greatly shorten the time in the bottles it takes for the flavor the come into it's own.