First BIAB only achieved half the target OG - need help troubleshooting please!

[OldManTimbers]

Went for a one gallon Russian Imperial Stout last night with a target OG of 1.097 and only got around 1.055...a rough look. Wondering if you wonderful more experienced people can help a guy out to see what I did wrong. Here's what I had for my recipe:

4.2lbs malt, 7.2 grams hops
This is what the online biab calculators spit out and what I followed:
2.5 gallons mash water at 150 degrees for 75 minutes
1.1 gallons mashout water at 170 degrees
Boiloff rate at 1.25 gal/hour
90 minute boil
5 gallon kettle with a 12.5 inch diameter

I ended up with close to 2 gallons of wort at the end of the 90 minute boil and a disappointingly low OG, any help would be greatly appreciated. This was my first time cracking at an all grain/biab and want to do it correctly in the future. Does too much mash/mashout water affect the OG? Am I inputting my information incorrectly to the biab calculators? I read somewhere that I should be closer to 1.5 quarts per pound of mash water

 

[ATLBeer]

Well you ended up with about twice the water you expected, so the OG would be very low.

I suspect you didn't hit your estimated boil rate (1.875 total). What was your pre boil volume?

 

[Electric Brewer]

In my calculator, if the alternate between one gallon and two gallons post boil, it switches between 1.090 and 1.050. so yeah. You got twice the amount of water but still the same amount of sugar.

 

[tracer bullet]

Agreed too much water in the end. 1.055 in 2 gallons is sort of double that in half the gallons. Need to use less water to mash and / or boil, or boil longer.

2.5 gallons for 4 lbs grain sounds like too much. I'd say more like 1.5 or so would be appropriate off the top of my head.

 

[OldManTimbers]

Thanks a bunch for your replies folks. Is there a different way I should be calculating this? I'm concerned that my calculations were so far off. Also for next time, if my wort has too low of an OG at the end of the boil, should I keep boiling until I reach my target volume/OG? Thanks again.

 

[OldManTimbers]

Well you ended up with about twice the water you expected, so the OG would be very low.

I suspect you didn't hit your estimated boil rate (1.875 total). What was your pre boil volume?

My preboil volume was close to 3.2 gallons once I added the mashout water.

 

[DBhomebrew]

You need to figure out some parameters of your system. Every system and everyone's process is a little different, so all the rules of thumb are exactly that.

For a 1 gal batch, I'm assuming that's volume into fermenter. That's the start.

1gal VIF + whatever volume lost to kettle dead space = Post-boil Vol

Post-boil Vol + Boil-off = Pre-boil Vol

Pre-boil Vol + Grain Absorption = Total Water Vol

TWV can used in whole as a full-volume mash or can be split up among strike, sparge, step infusions, mash out, whatever. What's important for you now is to figure out that TWV.

Kettle dead space and boil-off rate can be found in a water-only 'dry' run. Grain absorbtion is probably close as your extract was pretty close to what you aimed at.

My guess is dialing in your boil-off will be your best next step.

FWIW, my boil-off is a mere ~.32gal/hr in a 12"dia kettle. I use a very gentle boil. Boil, yes, but gentle.

 

[BrewnWKopperKat]

This may be helpful when talking about boil intensity.

Boiling Wort Visual Reference:

Boiloff rate at 1.25 gal/hour

With my 1 gal batches, my boil off rate is around 1 qt per 45 min. But as @DBhomebrew suggested, everyones equipment is different.

 

[Electric Brewer]

My preboil volume was close to 3.2 gallons once I added the mashout water.

Now you know your boil-off rate is .8/hour.
Now you know your grain will suck in .4.

 

[OldManTimbers]

Now you know your boil-off rate is .8/hour.
Now you know your grain will suck in .4.
[/QUO

I really appreciate your help!

 

[RM-MN]

You're doing a BIAB batch. Mashout isn't needed at all. BAM, you just reduced the water by over a gallon.

Now lets look at sparging. You mashed the grains, drained the wort from the bag of grains and you measure the volume you have collected. You know that you used 2.5 gallons of water for mashing but the grains will have absorbed some so look at what you collected. Now think about how much you will boil off. Compare what will be left in the pot at the end of the boil. Enough for the fermenter? If so you have a full volume, no-sparge batch. If you are short on volume at this point, sparge with the amount of water you need. The sparge will collect more sugars from the grain but will dilute what you have already collected. That's OK as you will boil some off to concentrate it again.

 

[madscientist451]

The issue above has been identified as a water volume problem, but if the OP simply cuts the amount of water used, other problems could develop.
One of the issues with doing BIAB is maintaining mash temp. If your mash volume is low, like when if you are doing one gallon batches, its harder to maintain your temperature.
My 2 cents to the OP: Re-brew the above recipe, use the same amount of water and double your grain and hops.
If your OG after the boil is too high, you can add a some water to bring it down. Keep some DME on hand and if your gravity is too low you can add that. You'll have to pull a sample at the end of your boil, chill it down and take a gravity reading to determine what you should do.
There are on line dilution calculators you can use in case you need to add water.
Also, I use a little extra, water and grain in my recipes so I have about 1/2 gallon left in the bottom of my kettle that contains the hops and trub that I don't want in the fermenter.
A 3 gallon plastic fermenter is about $20 and works great for 2 gallon batches.
Also, was your mash water 150F or was that your mash temperature?

 

[Bobby_M]

The issue above has been identified as a water volume problem, but if the OP simply cuts the amount of water used, other problems could develop.
One of the issues with doing BIAB is maintaining mash temp. If your mash volume is low, like when if you are doing one gallon batches, its harder to maintain your temperature.
My 2 cents to the OP: Re-brew the above recipe, use the same amount of water and double your grain and hops.
If your OG after the boil is too high, you can add a some water to bring it down. Keep some DME on hand and if your gravity is too low you can add that. You'll have to pull a sample at the end of your boil, chill it down and take a gravity reading to determine what you should do.
There are on line dilution calculators you can use in case you need to add water.
Also, I use a little extra, water and grain in my recipes so I have about 1/2 gallon left in the bottom of my kettle that contains the hops and trub that I don't want in the fermenter.
A 3 gallon plastic fermenter is about $20 and works great for 2 gallon batches.
Also, was your mash water 150F or was that your mash temperature?

That doesnt make sense to me. The advice is to make twice the batch size you actually want?

You just track backwards from your desired batch size. Package volume + fermenter loss + kettlebtrub loss + cooling shrinkage + boil off + grain absorption = no sparge strike volume. Sounds like he was 1 gallon too high there.

 

[madscientist451]

That doesnt make sense to me. The advice is to make twice the batch size you actually want?

My advice is making 1 gallon sized batches presents some BIAB temperature issues, so simply reducing the water used may not solve the problem for the OP. Since the OP has already determined how much water he needs for a 2 gallon batch for his particular equipment, adjusting the amount of grain to make a 2 gallon batch will work out fine and be easier.
There are many ways to work around the 1 gallon batch size mash temperature problems, but its really much easier to go a little bigger and have some more thermal mass for the mash.

 

[BrewnWKopperKat]

Insulate the kettle to hold the mash temperature. This technique really does scale down from larger batch sizes to 1-gallon-ish batches.

 

[ATLBeer]

My advice is making 1 gallon sized batches presents some BIAB temperature issues, so simply reducing the water used may not solve the problem for the OP.

Theoretically this could happen, but that wasnt the problem here, the ending sugar was very close to his target, it was just diluted due to excess water.

If he would have skipped the mash out water, it would have been just fine.

 

[RM-MN]

One of the issues with doing BIAB is maintaining mash temp. If your mash volume is low, like when if you are doing one gallon batches, its harder to maintain your temperature.

Maintain the temperature for how long? Until conversion is complete or until the hour or 90 minute mash period is over. These times are not the same.

 

[InspectorJon]

Many of us have found this to be a useful, accurate calculator for water volume needs as well as other related numbers.
Priceless Brew in a Bag Calculator

 

[doug293cz]

My advice is making 1 gallon sized batches presents some BIAB temperature issues, so simply reducing the water used may not solve the problem for the OP. Since the OP has already determined how much water he needs for a 2 gallon batch for his particular equipment, adjusting the amount of grain to make a 2 gallon batch will work out fine and be easier.
There are many ways to work around the 1 gallon batch size mash temperature problems, but its really much easier to go a little bigger and have some more thermal mass for the mash.

Many brewers find that small volume mashes can be put in a warm oven to hold temperatures better. No need to make things more difficult than necessary.

Brew on

 

[BrewnWKopperKat]

Many brewers find that small volume mashes can be put in a warm oven to hold temperatures better.

Yup - numerous interesting approaches for many common 1 gal brewing situations can be found over in "one gallon brewers unite".

The book Speed Brewing (2015) talks about brewing 2 gal BIAB batches targeting 1.75 gal kegs also uses an oven for holding mash temperature.

 

[Bobby_M]

Small batch holding temps....

Sous Vide drop in.
Oven rest at 170F.
Mash in a cooler
Wrap a mat heater around the pot.

 

[BrewnWKopperKat]

One of the reasons that I mention "one gallon brewers unite" for using the oven for mashing is that the idea is more detailed than "oven rest at 170F".

Holding mash temperature for 1 gal batches is a solved problem. But it's more involved than a couple of bullet points.