Partial mash temperature too low?

[etcetrah]

I did a partial mash last night and the intended temperature was 149F. I mash in a 2 gallon cooler and generally don't mess with it after I've put in the water and mixed the grain in well. Anyway, I started the mash with water at about 150F, which was good, but 45 minutes later, when I was drawing off the first wort, the temp had dropped to around 140F. How much difference will this make? Does the conversion of starch to sugar stop if the temps fall too low?

 

[ArcaneXor]

What was your original gravity? That should answer your question. But generally, you still get conversion at 140, it's just very slow.

Putting 150 degree water into a cold mash tun filled with grains is never going to give you a mash temp of 149.

 

[etcetrah]

I ended up with an OG about 5 points lower than my target, so the temps must have dropped too low by the end of the mash time.

Also, just to clarify, I added water to the cooler at about 163F, which settled out at about 150F after mixing in with the grain. The mash was at 150F when I put on the lid and started the timer.

As a follow up question, if I can anticipate a 10 degree temp drop in 45 minutes, can I start the mash at say 154F, knowing it will "pass through" the highly fermentable range of 147 - 150F? I was trying to mash at the low end of the spectrum.

OR, does anybody using a cooler have success adding hot water to the mash halfway through to keep the temp up?