New to Concocting original mini-mash recipes : question about sparging

I had done four batches of extract with steeping grains.

My 5th batch was with a buddy and (as per his recipe) we used 2.25 lbs of 2-row and 1 lb. Pale Cyrstal; steeped trying to keep it between 155-170 and then poured the sparge water over the grains into the pot. We got a ridiculously high OG: 1.102!!!! Now, this APA turned out mighty tasty ("bordering on Belgian style" by one taster) but we didn't expect such a high OG.

So, for my 6th batch, I tried concocting an IPA recipe from scratch which used 2 lbs. of Pale Malt, 1 lb. Cyrstal 60, and .5 lb. CaraPils. I started as I did for the 5th batch mentioned above: steep all grains trying to keep temp between 155-170. Thereafter, instead of pouring the sparge water over the grains into the bigger pot, I had an extra gallon of sparge water ready (at about 160-165 dF and dunked the already-steeped grains for 10 minutes before pouring the sparge back into the bigger pot. Again, well-above expected OG: 1.120!!!!!!!!!!!

I have a ton of reading (books and HBT posts) under my belt and more than the average amount of beer knowledge in my noggin, but not enough to figure out where these two batches went wrong. Mash temperature not steady enough? Not properly using the sparge water? Not using the correct volumes of water?

Any suggestions, ideas, comments, or other such constructive criticism would be greatly appreciated!

Cheers,
JWiC

at what point, temperature, & volume were these OG readings taken at? was there anything else added to the batch or just those grains?

Are you doing full or partial boil? When are you taking the OG reading?

Partial boil; taking the reading at the very end, even after top-off water.

topping off can dramatically throw off the OG since its difficult to mix wort & water effectively enough to get an accurate reading. if you're topping off, id suggest taking the hydrometer reading before, then calculating for the final volume
batch OG = post-boil OG * post-boil volume / batch volume

are you taking the reading <90F? above that, temp adjustments aren't very accurate.

Excellent. I will try that formula with the next batch (writing down in my notebook right now, in fact).

I've read that the yeast and/or starter and the cooled wort should be about the same temp (so as not to shock the yeast one way or the other) so I've been cooling the wort to the room temp (i.e. temp of the yeast/starter which has been sitting on my counter for 24+ hours). Ambient temp in my place is around 68-72 dF with the AC on. I have never taken a gravity reading 90+ dF.