Reasons for significantly different efficiency

[dude1]

I've been brewing with the BIAB method in two different ways recently and I'm looking for the reason for significantly different brewhouse eff.

Case 1: a couple of Pale Ales, 1-gallon batches, thin mash (1.68qt/lb, 3.5L/kg), steady single infusion losing 2F in 1 hour, minimal mash-out, heavy sparging and squeezing, little amounts of hops. BREWHOUSE eff, 79-80% every time.

Case 2: high gravity Double IPAs, 5 gallon batches, slightly less thin mash (1.44qt/lb, 3L/kg), even steadier mash temp losing 1F to none in 1 hour, no mash-out this time, slightly less effective sparging, huge amounts of hops that I caught in a strainer bag while transferring and then squeezed (little loss of wort). BREWHOUSE eff between 58 and 68%

I'm looking for the culprit.
Could the style of the beers explain these differences, as the second serie (5 gallon batches) was only big beers?

Thanks

 

[Gnomebrewer]

Rather than worry about the difference between the two, focus on improving your 5 gallon batches. Although efficiency shouldn't be the biggest concern for homebrewers (in the end it's only a few dollars worth of grain) you should easily be able to improve on 58 to 68% using BIAB with a sparge and little trub loss. Big beers will cause a significant drop in efficiency though.

Are you crushing your own grain? A fine crush will help significantly with getting starch extraction in a normal mashing timeframe. Getting your pH into a reasonable range will also help - are you using tap water, or RO? If using tap water, do you know what it's like? What are you doing for a sparge? Single dunk, fly, double dunk, quick rinse while the bag hangs etc. Are you squeezing your sack? That also makes a big difference.

You can start to identify the cause of efficiency issues by measuring your gravity at the end of the mash, to make sure conversion (and extraction of starches) is complete. Use this spreadsheet (mash conversion efficiency)
http://braukaiser.com/documents/efficiency_calculator.xls
Then measure gravity and volume at the start of boil for mash lauter efficiency.
That should help you see where your efficiency is taking a hit.

 

[Gnomebrewer]

To answer the question about big beers, yes they will have poorer efficiency. A brewer on here (Doug something) has a great spreadsheet that shows the drop in efficiency you can expect with different methods and gravities. I'll see if I can find it and post back.

 

[Gnomebrewer]

Here it is. Doug293cz is the creator. 0.012 gal/lb grain absorption is for no squeezing the bag, 0.06 is squeezed. It's for lauter efficiency (not brewhouse efficiency) so applies to the gravity and volume in the boil kettle. As you can see, even with a single sparge and at 4lbs of grain per gallon (a monster beer) you should be able to beat 70% efficiency with a single sparge and some sack squeezing. I'm assuming that this assumes a fine crush.

 

[dude1]

Thanks for the amazing answers.

Yeah, I crush very fine and try to sparge as well as possible, but there's definitely room for improvement at the sparging step.

By the way, Doug's table totally confirms what I suspected: most of the reason for the lower eff comes from bigger beers: my light beers had ~1.8lb grain per gal of pre-boil vol and my big beers ~2.67, which corresponds to the table.

 

[doug293cz]

Here it is. Doug293cz is the creator. 0.012 gal/lb grain absorption is for no squeezing the bag, 0.06 is squeezed. It's for lauter efficiency (not brewhouse efficiency) so applies to the gravity and volume in the boil kettle. As you can see, even with a single sparge and at 4lbs of grain per gallon (a monster beer) you should be able to beat 70% efficiency with a single sparge and some sack squeezing. I'm assuming that this assumes a fine crush.

This chart assumes nothing about conversion efficiency. Mash efficiency equals conversion efficiency times lauter efficiency. If you get 100% conversion efficiency, which is possible, then the chart also represents mash efficiency. Crush affects conversion efficiency.

Brewhouse efficiency equals mash efficiency times volume in fermenter divided by post-boil volume. A good name for fermenter volume divided by post-boil volume is transfer efficiency. Lots of hops will cause lower transfer efficiency, even if you squeeze the wet hops to reduce volume loss.

Brew on

 

[Gnomebrewer]

This chart assumes nothing about conversion efficiency. Mash efficiency equals conversion efficiency times lauter efficiency. If you get 100% conversion efficiency, which is possible, then the chart also represents mash efficiency. Crush affects conversion efficiency.

That makes sense. Unfortunately most brewers don't measure mash conversion efficiency so wouldn't know what their lauter efficiency is - only mash-lauter efficiency (the combination of the two). I think many brewers could 'hone in' on consistency if they measured both and mashed until conversion was complete (which it probably is after an hour for the majority of BIABers with a fine crush and half decent water).

 

[doug293cz]

That makes sense. Unfortunately most brewers don't measure mash conversion efficiency so wouldn't know what their lauter efficiency is - only mash-lauter efficiency (the combination of the two). I think many brewers could 'hone in' on consistency if they measured both and mashed until conversion was complete (which it probably is after an hour for the majority of BIABers with a fine crush and half decent water).

Absolutely. If you really want to diagnose efficiency issues, you have to measure your conversion and mash efficiencies, and then back calculate your lauter efficiency. Otherwise you won't know whether to try to fix conversion efficiency or lauter efficiency. Calculate conversion efficiency using the method here.

Although to be honest, lauter efficiency is usually less of an issue for no-sparge or batch sparge, since channeling is not an issue. Low mash efficiency in batch/no sparge usually comes back to poor conversion efficiency, for which the largest contributor is coarse crush.

Brew on