OG Well Under Expected

[MagicMike314]

Was hoping to get some advice and answers from experienced brewers!

First two batches went phenomenally, and today was the third batch. I was making a half recipe of a blonde ale (Blonde Ale - Tropical Blonde Ale) which posts the following recipe:

Size (Gallons): 5.5
OG: 1.046
Boil Size: 2 1/2 gal

Grain:
1 lb Crystal 10L
1/4 lb Honey Malt
Steep grains for 20 minutes at 155 degrees

Extract:
1 1/2 lbs Light DME @ 45 minutes
4 oz corn sugar @ 30 minutes
3 lbs Light DME @ flameout

Hops:
1/4 oz Mosaic (12.7 %) @ 45 minutes
1/4 oz Citra (14.1%) @ 10 minutes
1/2 oz Citra (14.1 %) @ 5 minutes
1 oz Citra (14.1 %) @ flameout

Additives:
1 tsp Irish Moss @ 15 minutes
___________________________________________________________________

Since this was a half recipe, I cut down to:
3/4 lb Light DME @ 45 minutes
2 oz corn sugar @ 30 minutes
1 1/2 lbs Light DME @ flameout
Without a kitchen scale (one is on the way to avoid this in the future) I followed some forums posted on here where it was suggested to use 2 cups of DME per lb. I have to believe this is where my mistake was made.....

After finishing, I took a reading of my wort and found the OG to be 1.020 (the posted OG was 1.046). I quickly boiled 1 1/2 more cups of light DME and brought the OG up to 1.032.

Now that this is fermenting and we will see what happens, can someone explain to me where I went wrong? Simply trying to avoid this for future batches.

 

[mcmeador]

This is going to seem like a terribly obvious question so forgive me for asking it, but you did cut your water in half as well, right? Using the full amount of water with the half amount of ingredients you indicated would put you right around 1.020. Otherwise, the only explanation I can imagine is that you used about half as much DME as you should have because your cups per pound estimate was way off.

 

[MagicMike314]

This is going to seem like a terribly obvious question so forgive me for asking it, but you did cut your water in half as well, right? Using the full amount of water with the half amount of ingredients you indicated would put you right around 1.020. Otherwise, the only explanation I can imagine is that you used about half as much DME as you should have because your cups per pound estimate was way off.

The water was cut in half as well! So a 2.75 gallon batch in the end of things. Is it worth getting some more DME or corn sugar to add to the already fermenting beer? I figured it was probably due to a bad cups per pound estimate.

 

[rburrelli]

Here is the simple math. A cup equals 8 fluid ounces. Therefore, 2 cups equals 16 ounces. This is where it gets murky. 16 ounces equals 1 pound but that is now a weight measurement not liquid. I have seen debates about this so best to get a scale going forward.

 

[D.B.Moody]

Without a kitchen scale (one is on the way to avoid this in the future) I followed some forums posted on here where it was suggested to use 2 cups of DME per lb. I have to believe this is where my mistake was made.....

I think you are right. The estimate I have written in the front inside of my brewing file folder is 2 3/4 cups per pound, but that's a note transferred to this folder from I don't remember where. (And probably based on decades old information.)

 

[mcmeador]

The water was cut in half as well! So a 2.75 gallon batch in the end of things. Is it worth getting some more DME or corn sugar to add to the already fermenting beer? I figured it was probably due to a bad cups per pound estimate.

I’ll let someone else answer that. I’ve never come across a situation where I felt it necessary to drive up the gravity, much less after fermentation began. If you were to do that, you would definitely want to sanitize it before adding it.

 

[dbsmith]

What temperature did you take your gravity reading at?

 

[Dgallo]

If everything was genuinely cut in half it should have been absolutely equivalent, so something. Did you remember to step your grains? Because you make no mention of the steeping grains in your half recipe above.

Also yes, don’t use volume measurements as weight measurement. Dry ingredients can be packed looser or tighter and effect weight. That’s a huge difference you’ve experience, less than half the expect gravity, so that can’t be your only mistake

 

[Holden Caulfield]

I followed some forums posted on here where it was suggested to use 2 cups of DME per lb. I have to believe this is where my mistake was made.....

~3 cups per pound is very commonly posted as the volume of 1 pound of DME. As mentioned previously, this is very likely the reason why you missed your OG. In addition to measuring your ingredients by weight rather than volume, a way to ensure you hit your target OG is to measure your preboil OG and make adjustments prior to the boil.

 

[marc1]

Measuring weight by volume is part of it, but the OG was waaaayyy low, how are determining your water/wort volumes? Something else could be off as well.

 

[Holden Caulfield]

Measuring weight by volume is part of it, but the OG was waaaayyy low, how are determining your water/wort volumes? Something else could be off as well.

Agree.

Did some math - assuming you used 2/3 the quantity of DME and you accurately measured 2.75 gallons of wort at room temperature in the kettle post boil...

2.25LBs DME x 44 x 2/3 = 66pts
.125 LBs Dextrose x 42 = 5 pts
.5LBs Crystal Malt (steeped) x 13ppg = 7 pts
.125 LBs Honey Malt x 28ppg (this should be mashed and has some diastatic power so let's assume it converted during the 20 min steep) = 3.5 pts

Total points in kettle ~82 / post boil volume of 2.75 gallons = 1.029 post boil gravity before adding additional DME. The 1.020 gravity you measured is far less than what would be expected if you used 2/3 the amount of DME.

Had you added the targeted amount of DME you should have ended up with an additional 34 points which would have boosted your OG to 1.042 which is fairly close to the recipe plan - the difference could be explained by the difference in expected extraction efficiency of the grains.

Given the missing gravity points, additional reasons for the low measurement include...

1. Post boil volume was actually higher than per the recipe (how did you measure and at what temperature)
2. The DME used was far less than 2/3 of what was required due to volume rather than weight measure
3. Gravity readings not accurate (many reasons for this dependent on tool used)
4. Extraction efficiency of the grains was far less than expected (although this can only contribute a little to the difference)

Probably some others, but impossible to pinpoint without actually knowing the weight of the DME added as well as confirmation of post boil volume and accuracy of gravity measurement.

 

[Dgallo]

Agree.

Did some math - assuming you used 2/3 the quantity of DME and you accurately measured 2.75 gallons of wort at room temperature in the kettle post boil...

2.25LBs DME x 44 x 2/3 = 66pts
.125 LBs Dextrose x 42 = 5 pts
.5LBs Crystal Malt (steeped) x 13ppg = 7 pts
.125 LBs Honey Malt x 28ppg (this should be mashed and has some diastatic power so let's assume it converted during the 20 min steep) = 3.5 pts

Total points in kettle ~82 / post boil volume of 2.75 gallons = 1.029 post boil gravity before adding additional DME. The 1.020 gravity you measured is far less than what would be expected if you used 2/3 the amount of DME.

Had you added the targeted amount of DME you should have ended up with an additional 34 points which would have boosted your OG to 1.042 which is fairly close to the recipe plan - the difference could be explained by the difference in expected extraction efficiency of the grains.

Given the missing gravity points, additional reasons for the low measurement include...

1. Post boil volume was actually higher than per the recipe (how did you measure and at what temperature)
2. The DME used was far less than 2/3 of what was required due to volume rather than weight measure
3. Gravity readings not accurate (many reasons for this dependent on tool used)
4. Extraction efficiency of the grains was far less than expected (although this can only contribute a little to the difference)

Probably some others, but impossible to pinpoint without actually knowing the weight of the DME added as well as confirmation of post boil volume and accuracy of gravity measurement.

This is true. Also in his half recipe he does show his half grain total. If he forgot to steep the grains that would account for roughly another missing 25% of his gu points

 

[Tobor_8thMan]

I used BeerSmith Adjust Gravity tool.

If I'm understanding correctly, I use 1.032 for the OG, Volume 5.5 gal and Target Gravity 1.046.

BS indicates the recipes needs 1.75lb DME to achieve the desired OG.

If I got the info wrong, please correct and I will run the numbers again.

 

[Holden Caulfield]

If I got the info wrong, please correct and I will run the numbers again

OG deficit 14 points
5.5 gals * 14 points = 77 total points needed
44 point per pound of DME
Means you need 77/44 pounds of DME = 1.75

Looks good.

 

[MagicMike314]

Measuring weight by volume is part of it, but the OG was waaaayyy low, how are determining your water/wort volumes? Something else could be off as well.

Since 2.75 (a half batch of the recipe found online) was the batch size goal, I started off with 3.5 gallons, and started both the 20 minute steep and then afterwards the boil. When the boil came to a conclusion there was 2.5 gallons in the kettle so I simply added .25 gallons of boiled water to meet the expected volume.

 

[MagicMike314]

Agree.

Did some math - assuming you used 2/3 the quantity of DME and you accurately measured 2.75 gallons of wort at room temperature in the kettle post boil...

2.25LBs DME x 44 x 2/3 = 66pts
.125 LBs Dextrose x 42 = 5 pts
.5LBs Crystal Malt (steeped) x 13ppg = 7 pts
.125 LBs Honey Malt x 28ppg (this should be mashed and has some diastatic power so let's assume it converted during the 20 min steep) = 3.5 pts

Total points in kettle ~82 / post boil volume of 2.75 gallons = 1.029 post boil gravity before adding additional DME. The 1.020 gravity you measured is far less than what would be expected if you used 2/3 the amount of DME.

Had you added the targeted amount of DME you should have ended up with an additional 34 points which would have boosted your OG to 1.042 which is fairly close to the recipe plan - the difference could be explained by the difference in expected extraction efficiency of the grains.

Given the missing gravity points, additional reasons for the low measurement include...

1. Post boil volume was actually higher than per the recipe (how did you measure and at what temperature)
2. The DME used was far less than 2/3 of what was required due to volume rather than weight measure
3. Gravity readings not accurate (many reasons for this dependent on tool used)
4. Extraction efficiency of the grains was far less than expected (although this can only contribute a little to the difference)

Probably some others, but impossible to pinpoint without actually knowing the weight of the DME added as well as confirmation of post boil volume and accuracy of gravity measurement.

I simply measure the post boil volume by using the .25 gallon marks all the way up the side of the kettle. So far this hasn't been an issue whatsoever with batches in the past as they have been pretty accurate.

I use a cheap $10 hydrometer that came with the kit. It does seem to be a bit fickle and will even somewhat change its readings based on how you bob it around or spin it. Probably worth upgrading to a refractometer at some point?

Just so I'm understanding you correctly - point #2 is that the DME contribution could be even less than what I had incorrectly assumed (not even 2/3rds of the necessary DME) due to the faulty measuring?

 

[MagicMike314]

This is true. Also in his half recipe he does show his half grain total. If he forgot to steep the grains that would account for roughly another missing 25% of his gu points

For all of my shortcoming this batch - I did remember to steep the grains! I did it in the full volume which if I understand correctly shouldn't mess with the gravity at all, but might lead to harsh tannins. I'll be doing it in smaller volumes in the future.

 

[MagicMike314]

OG deficit 14 points
5.5 gals * 14 points = 77 total points needed
44 point per pound of DME
Means you need 77/44 pounds of DME = 1.75

Looks good.

Is it worth adding this extra DME (boiling, cooling and adding to the primary) after fermentation has begun, or cutting my losses and taking a much lower percentage beer?

 

[Dgallo]

Is it worth adding this extra DME (boiling, cooling and adding to the primary) after fermentation has begun, or cutting my losses and taking a much lower percentage beer?

As long as it’s still fermenting well do it.

 

[Holden Caulfield]

Is it worth adding this extra DME (boiling, cooling and adding to the primary) after fermentation has begun, or cutting my losses and taking a much lower percentage beer?

You made an Ordinary Bitter. It will be a little light on the flavor, but definitely drinkable. You can also enjoy a lot more in one sitting.

That being said, if you add additional DME, the yeast will certainly consume it providing more flavor and alcohol.

Bottom line it is up to you if the extra work at this point is worth it.

Note - the DME calculation was for a 5.5 gallon batch. If you have 2.75 gallons of 1.032 OG wort in the fermenter. To bring it 1.046 you will need to add...

2.75*14 = 38.5 points or 38.5/44 pounds of DME = .875 pounds. Before adding the DME you should boil it in about 16oz of water and then cool it to fermentation temperature before adding. Also, this will raise the volume of your wort, so you will be slighlty less that 1.046. To hit your OG you will need to add approximately 16/128*46/44 = .13 pounds more if you use 16 fl oz of water.

 

[Holden Caulfield]

Just so I'm understanding you correctly - point #2 is that the DME contribution could be even less than what I had incorrectly assumed (not even 2/3rds of the necessary DME) due to the faulty measuring?

Yes.

Fermentable points that make it into the fermenter do not boil away and points contribution of DME and LME are well known by weight. Furthermore they are added directly to the kettle so all the points make it into kettle; they are only lost when left behind when making transfers to other vessels. If you added 2/3 the DME and all the dextrose to the kettle that would be 71 points / 2.75 gallons = 1.025 OG from the sugars without any contribution from the grains. You measured 1.020 with the grains so something doesn't add up. Either you added less than 2/3rd the amount of DME, or your volume and or gravity measurements are off or some combination of a number of things. At this point it is impossible to determine. Going forward, one of the most important measurements are your preboil volume and preboil gravity as points can easily be adjusted (for mistakes in measurement and grain extraction efficiency) at this time to hit you OG.

 

[MagicMike314]

Yes.

Fermentable points that make it into the fermenter do not boil away and points contribution of DME and LME are well known by weight. Furthermore they are added directly to the kettle so all the points make it into kettle; they are only lost when left behind when making transfers to other vessels. If you added 2/3 the DME and all the dextrose to the kettle that would be 71 points / 2.75 gallons = 1.025 OG from the sugars without any contribution from the grains. You measured 1.020 with the grains so something doesn't add up. Either you added less than 2/3rd the amount of DME, or your volume and or gravity measurements are off or some combination of a number of things. At this point it is impossible to determine. Going forward, one of the most important measurements are your preboil volume and preboil gravity as points can easily be adjusted (for mistakes in measurement and grain extraction efficiency) at this time to hit you OG.

First of all thank you so much for all of your help (and others who have been incredibly helpful). I'm a big believer of trial by error - but knowing the why/how is very interesting to me.

I hadn't ever considered the option of preboil gravity - but I certainly will use it now! I'm assuming this means also starting with your final batch volume (to get a correct gravity reading) and then topping off with water after the boil? This seems like a very useful process just to make sure it's on the right track.

 

[mcmeador]

First of all thank you so much for all of your help (and others who have been incredibly helpful). I'm a big believer of trial by error - but knowing the why/how is very interesting to me.

I hadn't ever considered the option of preboil gravity - but I certainly will use it now! I'm assuming this means also starting with your final batch volume (to get a correct gravity reading) and then topping off with water after the boil? This seems like a very useful process just to make sure it's on the right track.

No need to do that. Just use a calculator like this:

https://www.brewersfriend.com/dilution-and-boiloff-gravity-calculator/
For example, whether you start with 3 gallons at 1.08 and boil off a gallon and top off with 3 gallons or start with 5 gallons at 1.048 and boil off 1 gallon and top off with 1 gallon, it’s all the same. The amount of sugar doesn’t change. Your end result will be a 5-gallon batch at 1.048.

Use the second calculator there to input your preboil volume, preboil gravity, and target batch size, and it will tell you what your gravity will be in the end.