Gravity and sweetness?

I was at my LHBS yesterday and they asked how I was making out with my Oatmeal Stout. I gave them the run through and told them that I was surprised by my FG.
My OG was 1.062 and after 10 days in primary where the airlock went from 2 bubbles per second to one every 70 seconds or so I racked to secondary for another 2 weeks. On bottling day I took a couple of readings and they came out to 1.026. I thought it would be lower and My LHBS seemed surprised also.

I was a little confused when she said , "well, see if it comes out too sweet."
What the hell does that mean?

Tommy

What's your recipe? That does sound a little high, i.e. you may have too many unfermented fermentables in there. I'll run it through BeerSmith if you'd like and see what your FG *should* have been.

It's a pretty popular kit at my LHBS.


7lb John Bull Amber Malt Extract
1 lb M&F Amber dry Malt Extract
½ lb M&F Roasted Barley Malt 675 L
½ lb M&F Black Patent Malt 471 L
½ lb Chocolate Malt 338 L
1 lb Flaked oats
1 oz. Yakima Magnum Hops (bittering) 60 min.
1 oz. Fuggles (finishing) 58 mins.
Wyeast # 1099XL Whitebread Ale yeast

I get an OG estimate of 1.061 (good job!) and a FG estimate of 1.018. Definately off a little. What temp did you take the FG reading at? Was this a 5 gallon batch (not 5.5, or 4.5)?

According to my stick on thermometer the temp was 70 degrees. I got five gallons in my primary but it was considerably less in my secondary and that's where I took my sample from. When I racked to bottling bucket I had 4.5 gals.

Tommy

I had the same problem, and it throws off the Hydrometer reading. Take notes, so next time you can add enough water next time to the batch so that your FG will come out right.

Umm, so Wagner..what did that actual mean (for us newbies out there).

My FG seemed a bit high at 1.018, but I didn't add any water after adding the original 3 gal to the wort to make 5 starting gallons.

In the end (some loss in bottling), I only ended up with a 12pk of 16oz bottles, and 27.5 12oz bottles, which was a bit less than I was expecting. SHould I have added water somewhere?

I didn't understand that response either, but I chalked it up to lack of knowledge on my part.
I started out with 5 gallons as I normally do. Then after racking to secondary and "being careful" not to get too much sediment into my secondary, I lose a little. Then the same thing happens when I rack to a bottling bucket leaving any remaining sediment behind. Before I do that, I stick a beer thief in the carboy (secondary) and take a sample for a hydrometer reading.
I'm not following what batch size at that point has to do with the reading. It's the same batch as in my primary just with a little taken out due to racking.

Tommy

If your sample came from a 4.5 gallon batch then the gravity reading would be expected to be a little higher than the Target specific gravity, because you have the same amount of the thicker unfermentables but they are floating in less water therefore the gravity is higher and never will reach the target gravity.

If you add .5 gallon of water then the gravity would be less. You are increasing the volume by 1/9th so your gravity would drop 1/9th of the difference between your gravity reading and 1.000.

(1/9 * .026) = .0028

if you add .5 gallons of water to your 4.5 gallon batch the gravity would drop to @ 1.0232. You would still be 5 points off. SO let it sit a while longer to finish up.

dougjones31 said:

If your sample came from a 4.5 gallon batch then the gravity reading would be expected to be a little higher than the Target specific gravity, because you have the same amount of the thicker unfermentables but they are floating in less water therefore the gravity is higher and never will reach the target gravity.

If you add .5 gallon of water then the gravity would be less. You are increasing the volume by 1/9th so your gravity would drop 1/9th of the difference between your gravity reading and 1.000.

(1/9 * .026) = .0028

if you add .5 gallons of water to your 4.5 gallon batch the gravity would drop to @ 1.0232. You would still be 5 points off. SO let it sit a while longer to finish up.

Click to expand...

Ok, I'm gonna be stupid now

Adding water would actually "change" the composition of the brew.
Taking some brew out of the carboy shouldn't, in my view.
If that were the case then how about when you take a sample for a reading. Your hydrometer is not floating in 5 gals or even 4.5, it's floating in just a few ounces or brew. By what you have explained above, why wouldn't that reading be different than if you floated the hydrometer in a 5 gal bucket?

So by what you are saying above it would seem that a 5 gal batch of brew being racked into a bottling bucket from a carboy, would have a hydrometer reading get higher as the carboy emptied into the bottling bucket?

My batch was 5 gals. My OG reading was from 5 gals. I would say that my FG reading was from 5 gals also, just with .5 gal removed...not evaporated, just left behind. I think it's density would remain the same.

Tommy

When you place the wort into the fermenter and you take a reading that is you OG. When the trub falls, there is now about .5gal of trub and not beer so that is going to throw off your reading. If you add .5 gal of water on top of the wort when you add it to the fermenter, you will at the end have a much closer 5 gal batch after the trub has fallen. Which in turn gives you a 5 gal reading and not 4.5.

I don't think it's a lack of water that's causing the reading to be off. Remember, his SG was spot-on with what it should have been - that would have been too high as well if his volume was off. Take a sample - is it still sweet?

the_bird said:

I don't think it's a lack of water that's causing the reading to be off. Remember, his SG was spot-on with what it should have been - that would have been too high as well if his volume was off. Take a sample - is it still sweet?

Click to expand...

It was never sweet to me. It was my LHBS that said it might be after they heard my FG. That's what made me curious about the connection between gravity and sweetness. This was after it was bottled.
None of my samples from brew day or rack to secondary or even bottling day were sweet.
The best description of the taste that I can give is "roasty/toasty with a touch of coffee and a little hop bitterness and after taste. Bottom line...pretty good


Tommy

Well, glad to hear that it tastes good. The concern is just that there are unfermented sugars in there. I'm surprised to hear you say, though, that the samples were not even sweet on brew day - do you mean they weren't OVERLY sweet, or sweet at all (wort ought to be sweet, it's all sugars).

So I've lost track - have you bottled yet? I would take the precaution of keeping those bottles in a rubbermaid or similar container, on the off chance that you *do* end up with the dreaded bottle bombs. I have a feeling you will be OK, but no need to take chances. It just seems that with that high an OG, there are still sugars in there that have yet to be consumed.

the_bird said:

Well, glad to hear that it tastes good. The concern is just that there are unfermented sugars in there. I'm surprised to hear you say, though, that the samples were not even sweet on brew day - do you mean they weren't OVERLY sweet, or sweet at all (wort ought to be sweet, it's all sugars).

Click to expand...

Not overly sweet, it tasted normal, good.

So I've lost track - have you bottled yet? I would take the precaution of keeping those bottles in a rubbermaid or similar container, on the off chance that you *do* end up with the dreaded bottle bombs. I have a feeling you will be OK, but no need to take chances. It just seems that with that high an OG, there are still sugars in there that have yet to be consumed.

Click to expand...

It's been bottled for six days today.

Tommy

Personally, I'd just keep a close eye on it for overcarbonation. Crack one open in a couple days, see where it's at. Do that every two or three days until the carbonation is "right" (wherever you want your stout to be), then keep them cooled. Better to err on the side of caution, IMHO.

Thats great man..hope it carbonates well and no bottle bombs! Rock on and enjoy!

Brewno said:

Ok, I'm gonna be stupid now

Adding water would actually "change" the composition of the brew.
Taking some brew out of the carboy shouldn't, in my view.
If that were the case then how about when you take a sample for a reading. Your hydrometer is not floating in 5 gals or even 4.5, it's floating in just a few ounces or brew. By what you have explained above, why wouldn't that reading be different than if you floated the hydrometer in a 5 gal bucket?

So by what you are saying above it would seem that a 5 gal batch of brew being racked into a bottling bucket from a carboy, would have a hydrometer reading get higher as the carboy emptied into the bottling bucket?

My batch was 5 gals. My OG reading was from 5 gals. I would say that my FG reading was from 5 gals also, just with .5 gal removed...not evaporated, just left behind. I think it's density would remain the same.

Tommy

Click to expand...

You're correct, the specific gravity is the same no matter what sample size you are reading it from because the sugars are in solution. I may be wrong, but what I think he was referring to was the original quantity into the primary. If your boil is short of the 5 gallons, and most recipes call for a 5 gallon ferment, then your gravity readings will be off a bit. The connection to sweetness is that the yeast consume the fermentable sugars and convert them into CO2 and alcohol. If the fermentation is not relatively complete, you will have fermentable sugars left over in solution, hence the sweetness question. The problem with this is, as someone else stated, you could be looking at bottle bombs due to the amount of unfermented sugar left. The remaining yeast will go to work, when bottled, and you would have an over-carbonated brew which could easily cause the bottles to explode. Remember, that from the yeasts point of view, the bottles are a concave structure which makes it fairly easy for the little critters to bust out given enough pressure.

I would definitely check the bottles periodically to check the carbonation level and get them cool once they are good.

Just when I thought everything went well
Now, if i never used a hydrometer, like some homebrewers, I wouldn't even be thinking about it

Hopefully I don't have any exploding bottles. Now I have to be on the lookout.


Thanks

Tommy

Think of specific gravity this way.

Your wort has a predetermined amount of solids in suspension. This is determined by the type of malt extract or grains you use to make the wort. The gravity calculators take these solids into account and determine gravity by calculating how many solids are in each pound of extract of grain then it takes into account how much water you are using.

If you use 8 lbs of extract in 5 gallons of water you would have a certain gravity.

If those same 8lbs of extract were in 4.5 gallons of water the solids would be swimming in a smaller pool and the gravity would be higher because the solids are more crowded together.

This ain't rocket science.......

Ok, that's fine.

Explain then why his starting reading was spot-on, and the ending reading was high. The volume of liquid didn't change.

He said he had 4.5 gallons in the end......5 in the beginning. That looks like a change to me.

Ok...I know...he lost .5 gallons when he racked to the secondary. But when you loose this volume it does not take with it unfermented and unfermentable solids that were there in the original gravity reading.

Most of the .5 gallon that is lost is Yeast cells that grew during fermentation. The yeast usually multiplies 4X. This yeast absorbs water and the water is left behind(inside the yeast cells) when you rack.....no solids are absorbed by the yeast so you have the same amount of solids in the 4.5 gallons.

It is a catch 22, you never know how the person who wrote your recipe measured. Some people always start with 5.5 gallons in 5 gallon batches so the final volume is 5 gallons. This would make the gravity readings off if the volume is different.

I say drink the beer and pay attention to your gravity readings the next time you brew it. Gravity readings are just a guideline...they are not absolute rules. I have several brews that I never bother to take readings on...I have been brewing them over 10 years and I can just tell by the taste if they are ready.

If the gravity is as high the next time you brew this recipe then you should consider adding something like honey to the recipe if you want to lower the final gravity.

Your high final gravity could be something as simple as a bad batch of malt extract. This batch could have had an unusually high percentage of unfermentables in it..................combined with the loss of volume you experienced.

The beer that was lost to the trub had the same concentration of sugars, though - it wasn't as if he was just removing water.

OK. I am getting aggravated with your arguements.

Yeast cells are 90% water and the cell itself is not comprised of beer. Just like your skin cells are not made of primarily beer. It is pure water.

Yes, the yeast cells(when they are in suspension) absorb some of the solids in the beer and convert them, but the cell itself is made of mostly water like all other living animals on this planet. (Except maybe people from Boston! HA! hA!)

When the yeast cells multiply, they use water from somewhere to form the new cells. And the cells absorb water as they get larger.

The minimal amount of beer that he left behind on top of the yeast will not equal .5 gallons. I would estimate most of us leave only a pint of beer behind when racking, the rest is yeast and absorbed water in it. Most of the .5 gal was inside the yeast cells and was pure water.


Take my advice or not....I am not charging you for it! I don't care either way. I am just offering knowledge that I have acquired over the years.

............................ I will see if I can find some info on yeast , so you can read up and learn something.

Yes, but as the beer ferments the volume does not change. For this reason, the FG, if read from the same container as the OG doesn't need any account of volume loss, which is what this discussion was focusing on. Also, the solids are dissolved, not in suspension. This is why the density of the water changes, hence the SG. If it were just solids in suspension, then the liquid would have the same gravity. Since they are dissolved in the liquid it becomes more dense and raises the gravity.

dougjones31 said:

............................ I will see if I can find some info on yeast , so you can read up and learn something.

Click to expand...

You know.....

Forget it. Ain't worth it.

clayof2day said:

Yes, but as the beer ferments the volume does not change. For this reason, the FG, if read from the same container as the OG doesn't need any account of volume loss, which is what this discussion was focusing on. Also, the solids are dissolved, not in suspension. This is why the density of the water changes, hence the SG. If it were just solids in suspension, then the liquid would have the same gravity. Since they are dissolved in the liquid it becomes more dense and raises the gravity.

Click to expand...

Come on guys...THINK!
If you drop a pack of silica into the wort, it will absorb water and reduce the volume and raise the SG. This is basically what the yeast does as it multiplies.

And as far as the suspension VS dissolved issue......We could argue that too but it ain't worth it. Either way, in suspension or dissolved, the specific gravity of the water is changed.

Wilkepedia says, "Total dissolved solids are differentiated from total suspended solids (TSS), in that the latter cannot pass through a sieve of two micrometres and yet are indefinitely suspended in solution. The term "settleable solids" refers to material of any size that will not remain suspended or dissolved in a holding tank not subject to motion, and exclude both TDS and TSS.[1] Settleable solids may include larger particulate matter or insoluble molecules."

So do you think that BeerSmith and ProMash and all of the other programs we use to calculate expected FG don't take this into account?

clayof2day said:

If it were just solids in suspension, then the liquid would have the same gravity. Since they are dissolved in the liquid it becomes more dense and raises the gravity.

Click to expand...

The specific gravity of a substance is a comparison of its density to that of water. Imagine a gallon bottle filled with water, a second filled with feathers, a third filled with lead weights. There are equal volumes of material present, but the bottle with the feathers will weigh less than that containing water; the bottle with lead weights will weigh the most.

If I have ground cork suspended in water, you are saying that the specific gravity of the water would be the same. You forget that the cork is suspended in the water and a volume of that water is going to weigh less than pure water. If you check the gravity with a hydrometer the cork would help the hydrometer float and therefore the gravity would be less than that of pure water.

So suspended or dissolved particles do affect specific gravity readings.

the_bird said:

So do you think that BeerSmith and ProMash and all of the other programs we use to calculate expected FG don't take this into account?

Click to expand...

My guess is NO. But I have not reasearched it to be sure. I do not recall a variable for water loss in either one.

Well, then what's different about this particular situation? Why is it an issue with this particualr batch, when it usually is not? I do an extract batch, I hit the calculated FG, I hit the calculated FG within a fairly small range - not the variance the original poster realized.

The final gravity is high, for whatever reason, and I'm not convinced that it has been caused by the yeasts' normal growth.

Did you even read this thread or are you just wanting to argue?

I never said his whole variance was caused by volume related discrepancy. I said that the volume may have caused 1/3 of his variance. I suggested that most of his problem could have been as simple as a bad batch of extract that had unusually high unfermentable %.

If your variance is under .003 then you are on par with a .5 gallon volume loss variance.

Can't we all just get along-neck...

dougjones31 said:

The specific gravity of a substance is a comparison of its density to that of water. Imagine a gallon bottle filled with water, a second filled with feathers, a third filled with lead weights. There are equal volumes of material present, but the bottle with the feathers will weigh less than that containing water; the bottle with lead weights will weigh the most.

If I have ground cork suspended in water, you are saying that the specific gravity of the water would be the same. You forget that the cork is suspended in the water and a volume of that water is going to weigh less than pure water. If you check the gravity with a hydrometer the cork would help the hydrometer float and therefore the gravity would be less than that of pure water.

So suspended or dissolved particles do affect specific gravity readings.

Click to expand...

Not to throw fuel on this fire, though I don't think that's avoidable: Specific Gravity is a measurement (property) compared to the constant of water at a particular temperature. It factors in density which is also relative to mass & volume. Weight is not a factor, as weight is a measurement of FORCE. While cork suspended in water may change the total volume of the water due to displacing a portion of the liquid, it will not affect hydrometer readings because the density of the water will not be altered. For the science geeks, here is the formula for SG:

SG = ρ / ρH2O (3)

where SG = specific gravity, ρ = density of fluid or substance (kg/m3), ρH2O = density of water (kg/m3)

To make matters even more complicated, due to the international nature of this forum, Here is the US, density is commonly referred to as Pounds per cubic foot which is really inaccurate as, again, weight is a measurement of force. The real measure of density should be Slugs per cubit foot. In order to interchange, multiply slugs by 32.2 to get an approximate value of pounds per cubic foot.

Now if we really want to argue, ask a physicist to define centrifugal force...

I agree that scientific definitions can be confusing. I would have to also take up for my cork analogy.

If the cork is suspended in the water in small particles, then wouldn't it make sense that the cork would impart a certain upward force on the hydrometer. This upward force would make the gravity readings different than that of pure water.

Weight and mass are commonly however incorrectly used interchangeably. I apologize. It is a bad habit that I seem to have a hard time shaking. But since we are not comparing brewing on the moon with brewing on the earth, the arguement is null.

The english word "weight" is equivalent to "Mass"...the only time it is different is when weight is used in science to describe a particular force usually caused by gravity.

What is your mass? 170 lbs
What is your weight? 170 Lbs

The only time they would be different is in different gravities.

You threw fuel on the fire and I put it out again.....anybody else?

Because centrifugal force exists only in rotating reference frames, but not in inertial reference frames, it's sometimes called a "fictitious" or "pseudo" force even though it is real indeed.

Centrifugal force is not a fundamental force. It exists in some reference frames and not in others. When it does exist, it is due to the acceleration of the mass of an object. Since mass is the source of an object's inertia (Newton's first law), the centrifugal force is an inertial force.

The first term on the right, Fi, is the applied force in the inertial reference frame, which we defined above. The second and third terms are forces that arise in the rotating reference frame:

Feff = Fi - 2m w x vr - m w x (w x r)


- 2m w x vr is the Coriolis force

and

- m w x (w x r) is the centrifugal force

Hopfan said:

While cork suspended in water may change the total volume of the water due to displacing a portion of the liquid, it will not affect hydrometer readings because the density of the water will not be altered.

Click to expand...

.....Agreed

OK then....

Does dissolved Carbon Dioxide affect specific gravity?

You cannot just simplify complex reactions to suit your misconceptions.

dougjones31 said:

I agree that scientific definitions can be confusing. I would have to also take up for my cork analogy.

If the cork is suspended in the water in small particles, then wouldn't it make sense that the cork would impart a certain upward force on the hydrometer. This upward force would make the gravity readings different than that of pure water.

Click to expand...

That would only be true if the cork adhered to the hydrometer. Not sure if surface tension applies within a liquid, but the particles would have to be extremely small so as to become a solution in the water and not just diluted in it.

Your volley...