Agree with both of the above. I brew in a bag, so I mash in the kettle, on my stovetop. When I want a very efficient mash I usually start at 158°F and just let it drop for 60-90min till it gets to around 144°F. Works great for me. If you let it get above 170°, you're in danger of denaturing the enzymes and not being able to convert any of the starches to fermentable sugars. If you leave it below 140°, the enzymes will just sit there and not do anything. As long as it's between 145°-158°F for 20min or so, you should be good. Check that hydrometer. And as always, RDWHAHB. Cheers.
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