In the May-June 2013 issue of BYO I detailed a home project titled “Jacketed Mash Mixer” about how to build a mash mixer. I used to get 75-80% mash extract efficiency with my previous equipment but I have been getting at least 90% since I started using my mash mixer. I have read that mash efficiency is supposed to be more a function of grain crush and lautering, but now I think the continuous mixing of grains is equally important as it helps to loosen starch out of the malt kernels and therefore increases extract yield. The only change to the process that correlates to this increase in mash efficiency is the use of the mash mixer. Same lautering method, amount of water to sparge and even grain crush.
The Wiz discusses the merits of mash mixers and offers some tips for fine-tuning your sparge.