Low Pre-boil Gravity and OG

[nunnlife]

Howdy,

I am having some troubles hitting my target gravity after mash. I have a cooler mash tun that keeps a stable heat just fine, but never seem to get a high enough gravity. Here is an example from yesterday.

- 14.25 lbs of grain (crushed nicely)
- Striked 5.34 gallons at 165°F
- Mashed for 60 minutes at 158°F (which was a bit hotter than my 154° goal)
- Drained pretty slow (didn't time this, but probably took 40 minutes)
- Sparged 3 gallons at 170°F after all the mash water was drained
- Drained sparge relatively slowly, but again did not time
- Pre-boil gravity of 1.036
- Ended up with 6.2 gallons of wort pre-boil
- Post-boil gravity of 1.042 at 4.75 gallons of wort

My target OG was 1.065, so I am off by a lot.
Also, my IBUs are high now (88 IBU) since the malt character is low.
Side question, would people add extra wort to secondary to balance out the flavor?

I don't have any pH readings on my water, but heard that is a possibility.

Any thoughts?

It started fermenting ~12 hours after pitching the yeast.

Thanks!

Tim

 

[TallahasseeBrew]

Poor grain crush perhaps? I was dealing with the same issue for a few brews, till i checked my rollers on my mill and found them to have slipped a bit, resulting in a rougher crush than i was using before. readjusted the rollers and i'm back to hitting my targets again.

 

[Gavin C]

A couple of things leap out right away.

Why the slow draining? Sounds like you're doing a batch sparge process. A slow drain is not needed. Just slow enough not to disturb the grain bed and avoid particulate getting into the BK.

Did you thoroughly stir after adding the sparge water.

What's your crush like. If you go finer that will up the efficiency. Finding the sweet spot, finest crush without getting a stuck sparge. That will up your mash efficiency.

Water pH is not a concern. It's mash pH which is important but is of minimal importance when you're talking about mash efficiency. It relates more to flavor.

 

[doug293cz]

Howdy,

I am having some troubles hitting my target gravity after mash. I have a cooler mash tun that keeps a stable heat just fine, but never seem to get a high enough gravity. Here is an example from yesterday.

- 14.25 lbs of grain (crushed nicely)
- Striked 5.34 gallons at 165°F
- Mashed for 60 minutes at 158°F (which was a bit hotter than my 154° goal)
- Drained pretty slow (didn't time this, but probably took 40 minutes)
- Sparged 3 gallons at 170°F after all the mash water was drained
- Drained sparge relatively slowly, but again did not time
- Pre-boil gravity of 1.036
- Ended up with 6.2 gallons of wort pre-boil
- Post-boil gravity of 1.042 at 4.75 gallons of wort

My target OG was 1.065, so I am off by a lot.
Also, my IBUs are high now (88 IBU) since the malt character is low.
Side question, would people add extra wort to secondary to balance out the flavor?

I don't have any pH readings on my water, but heard that is a possibility.

Any thoughts?

It started fermenting ~12 hours after pitching the yeast.

Thanks!

Tim

Assuming the weighted average of gravity potential for your grain bill is 1.036, and using your pre-boil volume and gravity, your mash efficiency works out to 43.5%. Using your post-boil volume and gravity, your mash efficiency works out to 38.2%. Mash efficiency pre-boil and post-boil should be equal, unless there was a volume loss to something other than boil off (you don't lose any sugar boiling.)

~40% mash efficiency is extremely low. In order to have that low a mash efficiency, your conversion efficiency almost has to be quite low. In order to calculate conversion efficiency, you need to have a gravity measurement on your first runnings. I describe how to calculate conversion efficiency here. Did you happen to take a first runnings gravity measurement?

Some things that may be (at least partially) responsible for your low conversion efficiency:

• Higher than measured mash temperature due to a thermometer that reads low. This could lead to premature denaturing of amylase enzymes.
• Mash pH less than about 5.2, or greater than about 5.8. Either could lead to a reduction in conversion rate.
• Dough balls due to insufficient stirring at mash in. Dough balls are effectively excluded from the mash, and get no conversion.
• Insufficient mash time for crush size. Larger grain particles take longer to complete conversion.

Brew on

 

[nunnlife]

This is all great insight. Thanks! Looks like I need to take a couple steps next time. Just to get things right, I need to:

- Make sure my grain is crushed fine enough
- Take a pH reading of my water to make sure it falls into between 5.2-5.8
- Make sure my mash temperature is no higher (or lower) than 154°F
- Stir the mash sufficiently while mashing and sparging
- Let my mash go for 90 minutes instead of 60 minutes
- Take a gravity reading of my first runnings to get more data

Any other insight to add to this?

Also, would you add more wort to my secondary to even out the flavor? Since my beer is going to 88 IBUs (Chinook, Cascade and Williamette), I figured this could even the flavor out. I could also add some more yeast too. Maybe, get a new wort and yeast ready in a secondary and rack the current beer on top of it. Is it worth it?

Thanks! Peace,

Tim

 

[Gavin C]

- Take a pH reading of my water to make sure it falls into between 5.2-5.8

...

No. Water pH is not important assuming your water is potable. Mash pH needs to be measured but this is the least of your concerns when it comes to efficiency

- Make sure my mash temperature is no higher (or lower) than 154°F

...

The mash temerature is planned based on the type of beer you want. 154F is kind of a happy medium for many types. I've mashed at temps as low as 149F and up to 156F for a single infusion mash. Don't restrict yourself to one temperature.

- Let my mash go for 90 minutes instead of 60 minutes

...

This is likely not needed. If the other mash mechanics are working a 60 minute mash at 154F would be more than plenty. This assumes a good crush. With a bad crush 90 mins will help but the easier more effective solution is to crush finer. (Not so fine as to facilitate a stuck sparge)

 

[kh54s10]

This is all great insight. Thanks! Looks like I need to take a couple steps next time. Just to get things right, I need to:

- Make sure my grain is crushed fine enough
- Take a pH reading of my water to make sure it falls into between 5.2-5.8
- Make sure my mash temperature is no higher (or lower) than 154°F
- Stir the mash sufficiently while mashing and sparging
- Let my mash go for 90 minutes instead of 60 minutes
- Take a gravity reading of my first runnings to get more data

Any other insight to add to this?

Also, would you add more wort to my secondary to even out the flavor? Since my beer is going to 88 IBUs (Chinook, Cascade and Williamette), I figured this could even the flavor out. I could also add some more yeast too. Maybe, get a new wort and yeast ready in a secondary and rack the current beer on top of it. Is it worth it?

Thanks! Peace,

Tim

Grain crush is important...
Water pH is only important in how it affects mash pH.
154 is pretty warm for the mash - depending on the recipe, a pale ale might be below 148 degrees.
Stirring is important.
Mashing for 90 minutes will make little or no difference. 60 minutes is plenty unless using pilsner, then the extra time is to drive off DMS.

I have no idea what you are talking about with extra wort.... or yeast??
I don't think there is anything to be gained in this area.

Check your grain crush #1
Check the calibration on your thermometers #2
Lower your mash temp #3 Too high leaves unfermentable sugars and sweetness.
Was the preboil volume and volume into the fermenter what the recipe called for? If you had low volume into the fermenter your gravity should be high, if you had too much volume your gravity should be low....

 

[doug293cz]

This is all great insight. Thanks! Looks like I need to take a couple steps next time. Just to get things right, I need to:

- Make sure my grain is crushed fine enough
- Take a pH reading of my water to make sure it falls into between 5.2-5.8
- Make sure my mash temperature is no higher (or lower) than 154°F
- Stir the mash sufficiently while mashing and sparging
- Let my mash go for 90 minutes instead of 60 minutes
- Take a gravity reading of my first runnings to get more data

Any other insight to add to this?

Also, would you add more wort to my secondary to even out the flavor? Since my beer is going to 88 IBUs (Chinook, Cascade and Williamette), I figured this could even the flavor out. I could also add some more yeast too. Maybe, get a new wort and yeast ready in a secondary and rack the current beer on top of it. Is it worth it?

Thanks! Peace,

Tim

As stated by others, water pH doesn't matter. It's the mash pH (measured at room temp) that is important. But, pH is probably a minor contributor to your low efficiency.

Make sure your thermometer is calibrated at around mash temperatures. If your thermometer is not reading correctly, there is no way you can control your mash temperature properly (or even know what it really is.) As already stated, mash temperatures can vary depending on whether you want a drier or maltier beer.

I also support doing a finer crush, but disagree with those who say a longer mash won't help. With a fine crush more than 60 minutes shouldn't be necessary, but if you have a coarse crush, and no easy way to crush finer, then a longer mash time can help.

I wouldn't add wort to a secondary, but you could add concentrated wort (from DME or LME) to your primary fermenter. The preferred way to deal with a pre-boil gravity that comes out lower than desired is to add DME or LME to the boil.

Brew on

 

[Savagejair]

Hey sorry just letting you known check your hydrometer in water first make sure it's accurate mine was 12 points off[emoji482]

 

[nunnlife]

As stated by others, water pH doesn't matter. It's the mash pH (measured at room temp) that is important. But, pH is probably a minor contributor to your low efficiency.

Make sure your thermometer is calibrated at around mash temperatures. If your thermometer is not reading correctly, there is no way you can control your mash temperature properly (or even know what it really is.) As already stated, mash temperatures can vary depending on whether you want a drier or maltier beer.

I also support doing a finer crush, but disagree with those who say a longer mash won't help. With a fine crush more than 60 minutes shouldn't be necessary, but if you have a coarse crush, and no easy way to crush finer, then a longer mash time can help.

I wouldn't add wort to a secondary, but you could add concentrated wort (from DME or LME) to your primary fermenter. The preferred way to deal with a pre-boil gravity that comes out lower than desired is to add DME or LME to the boil.

Brew on

Thanks again for all these great thoughts.

When you say, "you could add concentrated wort (from DME or LME) to your primary fermenter", would you add this during active fermentation? How would I calculate how much to add to get my desired gravity?

Cheers!
Tim

 

[Gavin C]

I would advise against adding anything more to this batch. It can cause more problems that it will solve not that fermentation is underway.

The better time to correct was in the boil kettle but that ship has sailed.

A better approach is to learn the lessons with the batch and improve the process next time round. The beer will still be a decent drinkable tasty brew if all other things are in good shape.

Like any brewer it takes a few brews to learn how to put the theory of brewing into practice and improving the process is a hugely enjoyable part of things for me.

Trying to correct things after the fact is not usually a good plan. Better is usually the enemy of good in these types of situations.

To each their own of course.

The amount of DME needed is too large and the volume of water need to disolve it will lower the netted gains. A major hassle by my estimation.

 

[nunnlife]

I would advise against adding anything more to this batch. It can cause more problems that it will solve not that fermentation is underway.

The better time to correct was in the boil kettle but that ship has sailed.

A better approach is to learn the lessons with the batch and improve the process next time round. The beer will still be a decent drinkable tasty brew if all other things are in good shape.

Like any brewer it takes a few brews to learn how to put the theory of brewing into practice and improving the process is a hugely enjoyable part of things for me.

Trying to correct things after the fact is not usually a good plan. Better is usually the enemy of good in these types of situations.

To each their own of course.

The amount of DME needed is too large and the volume of water need to disolve it will lower the netted gains. A major hassle by my estimation.

Thanks Gavin! I am going to take your advance and just sit on this one and enjoy a nice HOPPY beer this time around.

I did come across this article though:
https://www.homebrewtalk.com/showthread.php?t=444328

What are peoples thoughts on this? Sounds like similar to what I was asking. Have others tried this with success?

Peace,
Tim

 

[doug293cz]

Thanks again for all these great thoughts.

When you say, "you could add concentrated wort (from DME or LME) to your primary fermenter", would you add this during active fermentation? How would I calculate how much to add to get my desired gravity?

Cheers!
Tim

I'd vote with Gavin and leave the batch as is. But, since I like playing with the numbers, I'll go ahead and answer the question.

A room temperature solution of maltose is saturated at about 44% by weight. So a saturated solution is 44°Plato, which converts to 1.200 SG. About the best we could do is add some 1.200 OG wort to your fermenter. 0.75 gal of wort would bring you up to 5.5 gal total in your fermenter. 0.75 gal of 1.200 wort would have 200 * 0.75 = 150 gravity points. Since DME has 44 pts/lb, we would need 150 / 44 = 3.41 lbs of DME to make 0.75 gal of 1.200 wort. 0.75 gal of 1.200 wort weighs 0.75 gal * 1.200 * 8.329 lb/gal = 7.496 lbs. Since the solution is 44% sugar, the sugar weight is 7.496 * 0.44 = 3.298 lbs. Total water weight would be 7.496 - 3.298 = 4.198 lbs of water. 4.198 lbs / 8.329 lbs/gal = 0.504 gal of water => 2.02 qts. So, you could dissolve and boil 3.4 lbs of DME in 2 qts of water for a couple of minutes and have about 0.75 gal of 1.200 OG wort.

The new wort has 150 gravity pts, and the original wort has 4.75 * 42 = 199.5 pts, so the total points would be 150 + 199.5 = 349.5 pts. The resultant SG would be 349.5 / 5.5 = 63.5, so the resultant SG would be 1.063 - 1.064. Not too far from your original target of 1.065.

Brew on

Edit: corrected calculations

 

[Gavin C]

I'd vote with Gavin and leave the batch as is. But, since I like playing with the numbers, I'll go ahead and answer the question.

A room temperature solution of maltose is saturated at about 44% by weight. So a saturated solution is 44°Plato, which converts to 1.200 SG. About the best we could do is add some 1.200 OG wort to your fermenter. 0.75 gal of wort would bring you up to 5.5 gal total in your fermenter. 0.75 gal of 1.200 wort would have 200 * 0.75 = 150 gravity points. Since DME has 44 pts/lb, we would need 150 / 44 = 3.41 lbs of DME to make 0.75 gal of 1.200 wort. 0.75 gal of 1.200 wort weighs 0.75 gal * 1.200 * 8.329 lb/gal = 7.496 lbs. Since the solution is 44% sugar, the sugar weight is 7.496 * 0.44 = 3.298 lbs. Total water weight would be 7.496 - 3.298 = 4.198 lbs of water. 4.198 lbs / 8.329 lbs/gal = 0.504 gal of water => 2.02 qts. So, you could dissolve and boil 3.4 lbs of DME in 2 qts of water for a couple of minutes and have about 0.75 gal of 1.200 OG wort.

The new wort has 150 gravity pts, and the original wort has 4.75 * 42 = 199.5 pts, so the total points would be 150 + 199.5 = 349.5 pts. The resultant SG would be 349.5 / 5.5 = 63.5, so the resultant SG would be 1.063 - 1.064. Not too far from your original target of 1.065.

Brew on

Edit: corrected calculations

Good stuff Doug. I was trying to work this one out earlier and came up with roughly 3.5 lbs of DME in a gallon with some boil-off. I thought to myself, if i put in this figure in my reply Doug will correct it mercilessly.

I figured you wouldn't be able to resist playing with the numbers. Like a cat with a ball of yarn. Nicely done. Keep 'em coming.

 

[doug293cz]

Good stuff Doug. I was trying to work this one out earlier and came up with roughly 3.5 lbs of DME in a gallon with some boil-off. I thought to myself, if i put in this figure in my reply Doug will correct it mercilessly.

I figured you wouldn't be able to resist playing with the numbers. Like a cat with a ball of yarn. Nicely done. Keep 'em coming.

Love those balls of yarn

For extra credit find the minor inconsistency (or is it a mistake ) in the calculations. I already had to edit it 3 or 4 times to get it as close to correct as it is. It's easy to tie your brain up in knots (yarn of course) trying to get the sugar balance right.

Brew on