I usually hit between 70% - 80% efficiency with my BIAB system but last weekend after my mash I found I had hit an efficiency of around 57%! It took a nearly two hour boil to get my S.G. back in the right ball park!
I'm rather baffled by this as I was just doing the same process as normal. The only thing I could think of (other than losing a kilo of grain down the back of the couch) is that I was using a large amount of wheat for the first time:
2.4 kg Minch Pale Malt
1.5 kg Torrified Wheat
1kg Minch Wheat Malt
200g Flaked Oats
27l of water
My understanding is that I could just mash all this at 65 degrees. Have I missed something?!
Post your actual readings, and double check the ppg values of your malt versus your software.
You are not using a high amount of wheat.
My guess is that there was some misreading when weighing your grain. You wouldn't be the first (if that is what happened)
Did you use rice/oat hulls? I'd imagine with 50% and oats it was pretty sticky. Did you hit your pre boil volume?
Are you taking a hydrometer reading while the wort is at boiling temp? You'll get a lower reading if it's not cooled down just. That might be your problem.
Crush on grains? If you did anything with your mill or bought in pre crushed grain it could be the problem.
I was using pre crushed grain from the Home Brew Company so didn't really weigh most of it other than the 200g of flaked oats and subtracting 100g from the 2.5kg of pale malt. I guess the weights could have been incorrectly marked on the bags... I didn't inspect it very carefully but it did appear to be crushed. By the time the mash was over it was a bit late to go back and check the weight!
I was using Brewtarget which said I should be getting a boil volume of 24.6l and a boil S.G. of 1.048
I ended up with a boil volume of 24l but an S.G. (adjusted for temperature) of 1.037
After a roughly 2hr boil I ended up with a volume of 17l going into the fermenter with an S.G. of 1.053
I ran the recipe through Brewer's Friend today as well with generic wheat and pale ale malt and it generally agreed with the figures generated by Brewtarget. To account for that discrepancy in S.G. I would have to have a yield of 0% for one of my grains!
The mash was not as sticky as I was expecting it to be - it seemed to drain well. Maybe that's a bad sign!
I guess I'll just have to try it again sometime and see if the same thing happens. Also I need to pay more attention to my initial grains rather than just dunking them in!
What efficiency did you set brewtarget/Brewer's Friend for? It is normal to assume 70-75% efficiency - you may have set it to 100%
Nope, set it to 75%
Whole Torrified wheat is quite round, might you have presumed it was pre-crushed & just threw it in like that?
Check the order to make sure it was crushed you ordered?