OG much higher than expected. What happened?

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?

This also happened to me today with my dunkelweizen. I was shooting for an OG of 1.051 but ended up with 1.075 according to my refractometer. I'm interested to hear what some of the more experienced guys have to say about this.

Can excess particulates give a false refractometer reading?

Thread is here if anyone wants more info: https://www.homebrewtalk.com/f12/ag-newbie-dunkelweizen-126083/

Did you use software like beersmith or promash? If so, did your "intended" numbers match your brewhouse efficiency?

What temp was your readings @? Usually hydrometers are calibrated for 60 degrees f.

I don't use software to brew, but I calculated my efficiency as 83%, which seems a bit high. All my hydrometer readings were temperature corrected.

I usually plan my recipes for 75%, but 83% is reasonable. I think Jamil's recipes are formulated for 70%, so that would explain why your OG would be higher.

I'm amazed that raising the sparge temp increased the efficiency that much.