I started AG brewing back in December after a two year hiatus. When I first started home-brewing I always ignored the hydrometer and careful measurements. I always ended up with drinkable beer, but this time around I became more interested in the science of brewing and proper procedure. I've made over 10 batches since the beginning of December and seem to have problems with efficiency consistency.
The OG gravity of the first two AG batches I brewed came out on target. The second and third batches were about 7-10 points lower than estimated. The 4th batch was within one point from the predicted gravity. I used the same calculator for my strike and sparge water volumes. I've always used a ratio of 1.33 quarts of water per pound of grain and have been able to maintain the targeted mash temperature to within a degree for 60 minutes . I even used the same fly sparge technique for each batch.
I then decided to use the water measurements from Beersmith and modify my efficiency from 72% to 65% for my next 6 batches. I used the same mashing and sparing techniques that I previously listed. Half my beers still come out about 7-10 points lower than predicted. I've tried maintain consistency from brew to brew, but I'm becoming irritated at the discrepancies. I usually end up with 5 gallons in the fermenter, give or take a pint or two.
I guess I can take a pre-boil gravity reading and compare it to the estimated pre-boil gravity in Beersmith, which I haven't done yet. I assume this would help me in determining if the problem is with mashing or the boil. I'm also tempted to give Batch Sparging a go, I've just been hesitant because I'm afraid I'll knock apart my CPV manifold when stirring up the sparge water.
Any input and suggestions would be appreciated. Thanks in advance.