Question:
I just brewed my first batch of all grain and I’m not sure why my efficiency was so poor.
Oatmeal Stout
13 lb grain bill (12 grain, 1 flaked oat)
4 gallons H2O @ 165 degrees for 30 min
1.5 gallons sparge @ 175 degrees
60 min boil
My OG is only 1.035.. I was expecting 1.070 to 1.075
I used the short mash to keep from getting any bitter flavors from the dark roasted malts. What did I do wrong?
Answer:
I think the main problem was not mashing long enough. In general, you should mash for at least one hour.
You can always do the iodine starch test to see if conversion has gone to completion. I don’t use this myself but I have some friends who routine do this test and it works well for them.
I also wonder if you should have used more water.
I use the rule of thumb I learned was that you should use 1.33 quarts of water per pound of grain with the water temperature 11 F above the desired strike temperature. I’ve used this relation a number of times and my strike temperature have always been at target.
For a strike temperature of 154 F with 13 pounds of grain one should add 17.3 quarts of ~165 F water.
Since you used 16 quarts I suspect your mash temperature may have been a bit too low though I’m not sure exactly what sort of temperature you would end up with. It may very well still have been within the standard mash temperature range.
I also believe that you may not have used quite enough sparge water. Generally speaking, one will use about the same amount of sparge water as your overall batch size. In you case it would be about five gallons.