Would brew bag size vs kettle size affect efficiency?

[linusstick]

I can't get past 66%mash efficiency after 7 beers. My brew bag is a lot bigger than my kettle. When I mash in I stir heavily for a few minutes and always hit my target temp (151 on my last beer). I pull the sides of the bag up so it is not clumped on the bottom. I usually lose some heat and my last beer dropped from 151 to 146. A lot more than usual. I mashed outside for the first time but the outside temp was in the 80s as opposed to in my house which is low 70s. With 4.7 lbs of grain (I do 1.5 gallon batches) I hit hot 1.046 preboil gravity as opposed to the 1.045 that Beersmith estimated. My question is two fold. First what more could I do using BIAB to increase my efficiency? I make sure my grain is crushed fine and usually hit my targets. Second if I have my efficiency entered as 65% in my equipment profile on Beersmith, it is calculating the water and grains to hit that value. How do you increase it? More importantly, with how small of batches I'm doing if it's always going to be 65% will that just mean I need to use more grains to hit my targets? With the small amount I use I could spare the extra dollar or so. Thanks

 

[pricelessbrewing]

Bag size will if it's too small.

Kettle size has a very weak effect on efficiency, as wider kettles will have a higher boil off rate.

 

[tofuguy]

Three things that really boosted my efficiency were...
1. Are you getting full conversion? I test EVERY batch before calling the mash complete with an iodine test. (Brown=complete, black=not complete)
2. The finest of the crush. Try crushing your grains at a smaller setting on the grain mill.
3. Mash pH. There is an article on the homepage of homebrewtalk.com that will get you started if you have not explored water chemistry.

Before I worked on the last two items, I was at the same efficiency as you for nearly 1 year. I did not have a BIAB setup (used a cooler mash tun) and was concerned of the finer mash, but afterwards, I starting to get into the mid-70s with the occasional 80+. Good luck.

 

[doug293cz]

I'm assuming the 65% efficiency is your brewhouse efficiency. Brewhouse efficiency is strongly affected by the amount of wort & trub left in your boil kettle.

Brewhouse Efficiency = Mash Efficiency * Fermenter Volume / Post-Boil Volume (including trub)​

With small batches, it doesn't take much volume left behind in the kettle to kill your brewhouse efficiency.

If it's your mash efficiency that is around 65%, then your issue is almost certainly poor conversion of starch to sugar (incomplete conversion.) The main fixes for low conversion are: finer crush, longer mash, get mash pH in the range 5.3 - 5.7.

Brew on