I have been noticing that when i use a large portion of specialty malts i tend to have decreased efficiency. All my parameters are controlled. All grain: PH, 1.75qts/lb, crush is good. I batch sparge and mash for 75min and have be up to 10% lower on my efficiency. I have yet gone through a "brewhouse efficiency" test to try and figure out at what stage i have having issues ( conversion or lauter) but i am assuming its conversion. So ? is do any of your ladies have issues when using higher levels of specialty malts with conversion? Also i am assuming that higher roast malts have less enzymatic power? my most recent was an southern english brown. 64% MO, 12.9% C80, 8% C120, 6.6% special roast, 4.8%pale chocolate, 3% carafa ll. mashed at 148F 75 min.