How important is mashing out? I am using a rectangular icechest with a copper manifold. When I go to sparge I am having trouble getting my grain bed to raise temp. I am mashing at around 154 and when I sparge my temp seems to drop because I am opening the top of the cooler. What temp should my grain bed be and how crucial is this? I am sparging with 170 degree water.
Thanks,
Scrib