Originally Posted by SouthernBrew
When sparging I have always read not to go above 170 degrees to prevent pulling unwanted flavors from husk material into the wort. I have always sparged at 170 and often noticed a slight astringency taste to beers I make especially with the lighter ones. I always monitor PH so that should not be the cause in this off flavor.
About 2-3months ago something dawned on me. What if I needed to correct for altitude? I am 1,000' above sea level and with correction I assumed that I should drop my temp 2 degrees on the sparge to 168 degrees. Since then I have brewed 2 batches of beer that I sparged at 167-168 degrees and they are a couple of the smoothest I have ever tasted.
Can someone confirm or deny my method of thinking?
You monitor the pH of the sparge runnings? That's where astringency comes from typically. You want the pH under 6 even at the end of the sparge.
Since you can even boil grain (like a decoction), the temperature isn't that important. It's more of a combination of factors- you want to keep the temperature AND the pH low. If the pH is low, you can even boil the grain without pulling tannins and having astringency issues. But if the pH is high, a higher temperature would exacerbate that and result in tannin extraction.
You can try sparging cooler and keep it up, since it works. But I would double check the pH of the sparge runnings because I think that's more of the issue.