[flbrewer]

Is there any potential negative effects from over stirring the mash to bring the temp down?

[denny]

Not that I'm aware of based on my own experience.  Done it many times.

[toby]

Not that I've ever seen, and that's how I do it.  Better than adding cold water and overshooting the adjustment the other direction.

[HoosierBrew]

Nope, no ill effects. I add ice a cube at a time when I overshoot. Works great, too.

[Black Sands Brewery & Supply]

Is there any potential negative effects from over stirring the mash to bring the temp down?

on a homebrew scale you're not going to harm it by over stirring to cool it off.

+1 on the ice method if i ever over shoot my temp.

But i recommend the past NHC seminar "biochemistry of the mash" recommends to not stir so i've just paid more attention into hitting my temp and not messing with it.

[mabrungard]

I can't envision a reason why stirring would be detrimental to the mash, excepting for the fact that it would create more opportunity for heat loss.

Mixing our mash is a big concern of mine. Getting a uniform distribution of heat and ionic content is a significant goal in my brewing. That is one reason that I recommend combining all mineral and acid additions to the brewing water before its combined with the grain. That way I can assure that those additions are completely distributed in the water.

Obtaining a uniform temperature through the mash is a little more difficult. Mixing grain and water together does make it possible to have hotter and cooler spots in the mash. With really good mixing, you can eventually get the temperature relatively uniform. But moving all the grain and water around is difficult. Another way to do it is to move only the wort via recirculation. Performing some vorlaufing or recirculation does improve the uniformity of the mash temperature. But without an external heat source, that action is likely to again result in heat loss. Brewers with RIMS or HERMS have a better opportunity to create and maintain a very uniform temperature in their mash.

Move the media or the liquid to improve mash uniformity. (moving the liquid is easier!) 

[GolfBum]

I don't see a problem stiring to get your temp down. You have to stir to mix in the grain so what is stiring a little more to bring the temp down a bit?

[klickitat jim]

Ask Mchrispen what he thinks. The Dunkel and Helles I sent him was continuously vorlaufed via pump for 90 minutes in a direct fire, false bottom mash tun, with flame on lowest setting that will hold the temp steady. (Usually about a quarter to half inch high flame, or as low as it will go without going out) The pump valve is usually at about half throttle, so i would estimate that the entire 5 or so gallons of mash recirculates about 30 times during a 90 minute mash. I've been told that I would get too dark of a color, burnt malt flavors, oxydation issues, and completely destroy the body and head retention doing that. Those would all be excelent reasons not to do it, if they actually happened. My only concern is chaneling, so I give it a stir when I add my grain, and I stir it once more about 15 minutes before runoff.

I would just avoid stiring to aggressively that you get a pile of foam on top. Mainly because it seems unnecessary.