I've brewed many recipes from Jamil Zainasheff's excellent book "Brewing Classic Styles" and I usually hit his OG (pre & post boil) and FG numbers right on the nose.
But last weekend I brewed his Blonde Ale recipe and my pre-boil and post-boil OG's were 11 and 12 points higher respectively. What happened?
I hit the mash temperature (single infusion), and did my usual batch sparge and let it sit for 15 minutes before lautering. The sparge temp was 157 degrees. The only thing I can think of is that I was worried I wouldn't collect enough wort and added 1.5L of pre-boiled water which raised the temp to 161F.
Is that what did it? Is this just a case of a fickle blonde?