Efficiency/Numbers etc

[BillyD]

I've moved to doing full volume BIAB recently and have done about 9 brews using the same method. Plugged the details into Brewer's Friend with a 70% efficiency and for the first 6 everything tallied, the last 3 brews though have been way off - one was 8 points off the OG and the last two (using the same grain bills) were both identical and 10 points off.

The only things that have changed with the last three brews are I am using a different hydrometer and I've used base malt (MO) from a different place, normally buy it online but the last three have used grain from a LHBS.

I've tested the hydrometer in water and it reads as it should so I've discounted that so I can see three possible factors causing the drop (in order of likeliness):

1) I'm doing things badly and so my efficiency has halved
2) The values in the calculator aren't the same as the grain I'm using
3) The grain is not very good

Anyone any ideas or input on what might be going on and what I can do to test or get to the bottom of it ?

 

[Brew_DD2]

Could be the crush or the age of the malt from your lhbs.

 

[BillyD]

Christ on a bike, just dawned on me that I bet I've been using uncrushed for the last 3 brews.

 

[Clint]

I wouldn't tell anyone....

 

[Leon103]

Christ on a bike, just dawned on me that I bet I've been using uncrushed for the last 3 brews.

That made me laugh.

Most likely the grain. Plus the software being slighty out

 

[stevey]

Perfect excuse to buy a grain mill

 

[BeerCat]

You got very good efficiency though considering. Would of expected it to be much lower. :hat:

 

[Oneiroi]

Christ on a bike, just dawned on me that I bet I've been using uncrushed for the last 3 brews.

It's only a matter of time before I do this

If that wasn't it, were the grain bills on the last 3 much bigger? On my third brew I didn't realise the grain:water ratio affected efficiency of extraction and split the mash with extra water when it wouldn't fit in my tun. After boiling it down to proper volume I found out I'd overshot my SG by 24 points! (The recipe had assumed a super low efficiency because it was a very large grain bill)

edit:grammar

 

[BillyD]

Very small grain bills, 1.26kg for the last two brews. I'll do another brew using the exact same grain bill but give the MO a couple of whacks with a brick and see if it helps.