Why is my OG always lower than expected?

[crash568]

Hi everyone, I have a question that I have been meaning to ask for a while now so being bored at work has prompted me to finally do it. So I have been doing BIAB for a little over a year now and done 15+ batches of 2.5 gallons. I would say 95% of the time I come in lower than my brewtoad numbers are showing me before hand. Just as an example let me break down my most recent batch to see if you guys see any issues in my process.

Hull Melon Pale Ale 2.5 gal

Mash @ 153*F for 60min in 3 gal of water
Sparge: Pull bag and squeeze then rinse with about a gal to bring volume to 3.5 gal preboil

Grain bill
5lbs of Pale Ale malt
.75 lbs flaked wheat

Hops all Hull Melon
.7 @ FWH
.4 @ 10 min
.5 @ 5 min
.4 @ FO

Yeast US-05

I had set my brewtoad setting to 65% mash efficacy because I know I have been getting lower than avg results and after my brew day was done I still came in at 1.041 OG any one have any tips as to how I can possibly fix this?

 

[flars]

My first thought would be the crush of your grains is to coarse for BIAB.

 

[jdauria]

Are you double crushing the grain? That can improve efficiency and many BIABers swear by it. Other thing that would help is to do a mash out at 168F for 10 minutes before doing your sparge if you can.

Do you use the same mash temp for every BIAB? Mashing a few degrees lower will also give you more fermentable sugar but could give you a drier beer than you want.

 

[crash568]

I have done some batches double crush and some only once through the mill and didnt really notice a difference. When you suggest the mash out at 168 do you apply heat to your kettle while the bag is resting on the bottom with all the grain in it?

 

[Rockn_M]

Like jdauria said...double crush your grain and increase your temp to about 165-168 for a few min before you sparging.

These 2 things increase my efficiency and was able to hit my OG.

 

[Rockn_M]

I have done some batches double crush and some only once through the mill and didnt really notice a difference. When you suggest the mash out at 168 do you apply heat to your kettle while the bag is resting on the bottom with all the grain in it?

That's it. I stir a bit more to keep the bag from sitting to long.

 

[crash568]

So I shouldn't worry about the bag melting or anything? I use a bag for my 8gal kettle from brewbag

 

[Gavin C]

You are probably already doing this but be sure you are taking gravity measures at the correct sample temperature. Too hot will skew the results giving a lower SG and calculated efficiencies will be off.

The calibration temperature is writen on the hydrometer. 60 or 68F is common.

Hydrometer Reading at correct temp.

In addition, are you confirming you have complete starch conversion in the mash.

A test for starch

A fine crush is important and will up your efficiency

My Crush (Double at a narrow setting)

 

[naturebrew]

You could try mashing longer, 90 mins should give you max extraction.

 

[crash568]

Thank you for all of that and I am doing all of it but you raised an interesting point I will need to go home and check now! The hydrometer, I always assumed it was calibrated to 68*F but have never looked for sure and I never wait for my wort to cool before taking a reading I just use a temp correction app to adjust to 68*F. When I go home tonight I will check and see if my hydrometer is rated at 60*F as that would probably account for a sizable change in my readings

 

[TexasWine]

Keep in mind temp correction gets less and less accurate the farther you get from the calibration temperature.

 

[Gavin C]

+1 The correction tools are only useful within a small range. I don't use them at all but that's just me

 

[RM-MN]

Try a 90 minute mash for your next batch. If your efficiency improves significantly you need to mill much finer. If you are getting the grains milled at your LHBS, you may need to find a new LHBS or get your own mill as your efficiency is so low that it makes me wonder if the grains are even milled.

 

[m00ps]

I second the short mash-out at ~168F. Also, I started noticing I got better efficiency with my BIAB when I washed the bag after removing it and squeezing it. I would dump a glass of cold water on it, squeeze the juices out, and repeat. Even though I added maybe 1liter of water, the OG definitely went up from the concentrated sugars left in the grain bag

 

[crash568]

when I say I dont get my wort to 68 I mean its usually at like 70-75 then I do the calculation its always at least close to pitching temp. I will try the 90 min mash next to see if thats the problem. Thanks everyone for your input this has helped immensely!

 

[Turkeyshot]

Hi everyone, I have a question that I have been meaning to ask for a while now so being bored at work has prompted me to finally do it. So I have been doing BIAB for a little over a year now and done 15+ batches of 2.5 gallons. I would say 95% of the time I come in lower than my brewtoad numbers are showing me before hand. Just as an example let me break down my most recent batch to see if you guys see any issues in my process.

Hull Melon Pale Ale 2.5 gal

Mash @ 153*F for 60min in 3 gal of water
Sparge: Pull bag and squeeze then rinse with about a gal to bring volume to 3.5 gal preboil

Grain bill
5lbs of Pale Ale malt
.75 lbs flaked wheat

Hops all Hull Melon
.7 @ FWH
.4 @ 10 min
.5 @ 5 min
.4 @ FO

Yeast US-05

I had set my brewtoad setting to 65% mash efficacy because I know I have been getting lower than avg results and after my brew day was done I still came in at 1.041 OG any one have any tips as to how I can possibly fix this?

When you rinse with your gallon of water are you only rinsing the grains the one time? If so maybe you should do it over a second pot or bucket and rinse the grains a few times to get all of the sugars off. Since one gallon for that much grain would be pretty thick and it just might not be rinsing all the sugars off. That might get you a few more points.

 

[crash568]

what I usually do for sparge is use my 2nd 5 gal kettle as a vessel and put the bag in there and dump my water in and stir it around then squeeze the bag dry and add the runnings to my boil kettle. What I am thinking I will do for my next batch is cut down on the mash water to 2 gal and then add extra sparge water to ensure I get the grain good an rinsed.

 

[Gavin C]

Am I right in reading that you have an 8 gallon pot and you are doing 2.5 gallon batches?

If so then you could do away with a sparge entirely and do a full volume mash. The thinner mash with a fine milling of the grain may get your efficiency up and improve the consistency.

 

[crash568]

I do have an 8gal kettle (I know its over kill for the batch size I do) I would do 5gal batches but only have the crappy electric stove top in my small apt. So you think doing a mash volume of 3.5 gal which is what I want my preboil volume to be is the better way to do it?

 

[Gavin C]

I do have an 8gal kettle (I know its over kill for the batch size I do) I would do 5gal batches but only have the crappy electric stove top in my small apt. So you think doing a mash volume of 3.5 gal which is what I want my preboil volume to be is the better way to do it?

Your mash volume with no sparge will be

Desired volume to the FV (batch size) + boil off + trub loss+ grain absorption

2.5g+(boil off unique to your system)+(this can be zero if everything goes into the FV from the kettle) + (amount will depend on how long it drains for or how much you squeeze)

I would guess you would be around 3.75-4 gallons depending on if you squeeze the bag or not, I squeeze and lose 0.04-0.045 gallons per pound of grain to absorption.

@pricelessbrewing has a great online calculator to work out all sorts of things. It is very user friendly. (it's in his signature)

If you are going to err on the side of caution, estimate the volume lower and do a small pour over sparge to reach your desired preboil volume. I don't but I have got my system pretty well dialed in at this point. The sparge can be with cold water so it is a very simple corrective measure.

Not sure if I'm making sense. Apologies if i am over complicating things. Check out the calculator. It is very good.