Gravity and sweetness?

[dougjones31]

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?

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.

 

[the_bird]

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.

 

[dougjones31]

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.

 

[Hopfan]

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

 

[Hopfan]

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.

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...

 

[dougjones31]

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?

 

[dougjones31]

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

 

[clayof2day]

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.

.....Agreed

 

[dougjones31]

OK then....

Does dissolved Carbon Dioxide affect specific gravity?

You cannot just simplify complex reactions to suit your misconceptions.

 

[Hopfan]

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.

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...

 

[clayof2day]

I think we are on to something now (with the cork). I think that both parties may be correct in this issue and it goes back to the idea of suspended solids vs. dissolved solids. I think that doug may be using a "true" definition of suspended solids, and the rest of us are applying scientific ideas to our empirical knowledge of "suspended". Upon reading some up a bit (not very much mind you) I think that by doug's definition of suspended solids they will indeed affect SG. Wheter yeast/trub/hop particulates fall into this category (as they can sediment out and be filtered out of solution) is what I find questionable, but I do not have or claim to know the answer.

 

[Brewno]

Ok, back to my possible bottle bombs

How about temperature, can that effect the reading.
When I took my OG after cooling my wort, topping off to 5 gals and mixing it up it was 1.062 at 78 degrees.
When I took my reading at bottling time it was 70 degrees and I got 1.026.

Tommy

 

[Hopfan]

Ok, back to my possible bottle bombs

How about temperature, can that effect the reading.
When I took my OG after cooling my wort, topping off to 5 gals and mixing it up it was 1.062 at 78 degrees.
When I took my reading at bottling time it was 70 degrees and I got 1.026.

Tommy

Who asked you!!!

Only kidding, to adjust for your OG at 78 degrees, add ~ .002 to your reading which gives 1.064. At 70 degrees, you should add ~.001 to your reading, giving a FG of 1.027. Hmm, 1.027 sounds a bit high. Have you checked to see how sweet it is? *ducking & running away rapidly*

 

[Hopfan]

I think we are on to something now (with the cork). I think that both parties may be correct in this issue and it goes back to the idea of suspended solids vs. dissolved solids. I think that doug may be using a "true" definition of suspended solids, and the rest of us are applying scientific ideas to our empirical knowledge of "suspended". Upon reading some up a bit (not very much mind you) I think that by doug's definition of suspended solids they will indeed affect SG. Wheter yeast/trub/hop particulates fall into this category (as they can sediment out and be filtered out of solution) is what I find questionable, but I do not have or claim to know the answer.

Alright, who invited the voice of reason? I believe you may be right, but then again, I believe that you're just jealous because the voices are only talking to me.

 

[Brewno]

Well I have the cases of bottles in a plastic garbage bag.

Have you checked to see how sweet it is? *ducking & running away rapidly*

Maybe I'll send you a bottle...with a timer on it!!

Tommy

 

[dougjones31]

I will apologize for my aggitation earlier....rough day at work. I have had a pint and a smoke and I am alright now.


Now back to the cork analogy. Say cork is ground to miniscule pieces. The hydrometer will push cork down and away from it as it goes down into the liquid. The pieces of cork have 4 direct forces affecting it; bouyancy, atmospheric pressure, friction and the resistance of the outside walls of the container. No matter what, some of those forces are going to end up pushing back against the hydrometer as they combine and counteract each other.

That is as deep into that scientific look at this as I am willing to go. Is that affecting the "Actual" specific gravity? Who cares? It will affect the perceived gravity of the person taking the reading and that is all we are talking about with any SG reading taken by a normal homebrewer with a hydrometer..


I will just say this.....

Yeast does absorb pure water from the wort and concentrates the wort which raises the specific gravity.

How much does that affect a 5 gallon batch? +/- .003 specific gravity from my quick calculation.

Did that make Brewno end up with 1.027 FG if the target was 1.018? No. If his FG was 1.021 then I would say that the volume reduction caused it completely.

Will Brewno have bottle bombs? Very small chance that he will.

Would I worry? no. I have had worse and never had an explosion.

What cause his FG to be high?
A) incomplete fermentation due to.....
1) bad yeast with low attenuation
2) not enough yeast piched
3) wrong temps
4) low nutrients in the malt extract
5) stalled ferment due to some other reason
B) high amount of unfermentables in wort due to....
1) bad batch of malt extract
2) bad adjuncts
C) concentrated wort

Now the bad thing is that it could be just a sum of all the tolerances of each of the above listed things. No one thing was the cause but it a combination of some or a little bit of all of the above.

The arguements thereof are useless.....we will never know.

 

[dougjones31]

Now if you really want to do something scientific then you could test beer bottles and see how much pressure the average bottle can take. Then you calculate how much sugar is left in a high FG brew. By that you can calculate how much co2 is going to be produced. Now take the amount of headspace in the bottle and then calculate how much pressure each specific gravity point would produce if the fermentation continues in the bottle.

You could figure out exactly how many points you can overshoot the target FG without risking having bottle bombs!

anybody? ..........Bueller?.................................Bueller?.....

 

[Hopfan]

The arguements thereof are useless.....we will never know.

I disagree. They are, at the very least, entertaining.

 

[Brewno]

What cause his FG to be high?
A) incomplete fermentation due to.....
1) bad yeast with low attenuation
2) not enough yeast piched
3) wrong temps
4) low nutrients in the malt extract
5) stalled ferment due to some other reason
B) high amount of unfermentables in wort due to....
1) bad batch of malt extract
2) bad adjuncts
C) concentrated wort

I don't know why it ended up high. Everything went well. My airlock was bubbling within 7 hours. By the next day it was going at a rate of two bubbles per second. It was very active all week and I had to extend my primary time to 10 days until it bubbled once every 70 seconds or so. Then it sat in secondary for 2 weeks.
My yeast was fresh and according to the date it was only about 3 days old, it was a smack pack. MY LHBS is very reliable as far as freshness goes on everything and they take pride in that.
As far as the wort being concentrated, well I posted about that somewhere here.
It was like extract it was so thick, I was really surprised because my other two batches weren't like that.

Tommy

 

[Brewno]

Here's an update.

It's been 17 days in bottles so far at 70-75 degrees and no bottle bombs.
I had a sample bottle yesterday and it wasn't bad. But then again I'm not really a stout drinker so I'm not sure what I'm looking for. I used to drink Guinness and liked it but I don't think that is close to an Oatmeal stout. I made this because I liked the oatmeal stout I tasted at a brewpub but after tasting their IPA which didn't taste like the IPA's I was used to, I realized I may not be able to compare mine to theirs. Theirs was creamy but also light in flavor, although very good.
I bought an Imperial oatmeal Stout brewed by "Stout brewery here in PA and didn't like it at all.
If i had to describe mine I'd say it's in between the two and definitely drinkable at this point, the Imperial wasn't IMO. Not to my liking.
Mine is strong though as far as flavors go, they're not subtle. Like a roasted expresso.

The only problem I see at this point is that the flavors are a little strong. But maybe that's how it is supposed to be?
It does have a smell of alcohol as well as an alcohol flavor though.
Maybe another two weeks will mellow it out.
I doesn't waste time giving a buzz though, I thought it was stronger in that regard than the SN Celebration Ale I've been drinking
That makes me wonder because my calculations gave me somehwree around 4.72% ABV and a beer that light in the ass never gives me a buzz.

Tommy

 

[dantodd]

Guinness is a pretty light stout, as sold in the US. I actually really like it on draught though many here don't.

A "real" stout is very different though but still had a fairly low FG. Imperial Stouts are a different animal all together!

I would suggest looking at the style guidelines on BJCP.org and then decide what you like from the descriptions. Brew based on your preferences and don't worry about staying "in style." But reading the styles will help you understand what you are tasting and will also help you pick out the bits you like.

 

[Hopfan]

An Oatmeal Stout will definitely be different than Guinness. As DT said, it is very different as served here. If you go to Ireland and get a draught there, you will enjoy it much more, but I prefer the Murphy's. Guinness uses a small percentage of "sour" beer in theirs to give it that unusual taste and Murphy's is more of a true stout taste. The buzz-factor is definitely an indicator, but I agree about brewing to your taste. I like to understand the styles but I like to brew & drink what tastes good. I also like to learn more about brewing, but I will never get to the point as some of the experts on this forum which makes it a great place to look for advice. There is no shortage of knowing folks willing to help. This place ROCKS!

 

[Torchiest]

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.

I know this is a couple weeks old, but I just saw it, and I wanted to make a couple comments. I can see how, if you were to put a hydrometer into your 5 gallons of liquid (including trub) primary and take a SG reading, it might, might be different than the reading you got if you put it into your post-racked 4.5 gallons secondary.

It seems, however, that you are saying that the actual amount of volume is what is affecting the reading. That is to say, if you took your 4.5 secondary, and racked half of that into a new seperate container, you would get a higher SG reading for the 2.25 gallon liquid. I just want to clarify that, because it must be incorrect.

The reason why none of that matters is because, whether or not you've got a 5 gallon primary with a half gallon of trub, or the 4.5 gallon secondary with no trub, normally, when you take a SG reading, you're just taking a couple ounces and putting them in your measuring vessel, so there is no trub to speak of anyway.

I imagine if you swirled all the trub back into your wort, it would make a huge difference in the SG reading, but otherwise, since it is seperated out, it wouldn't make a difference. Just as pouring clear water onto a dried out mud bed wouldn't change the SG of the water that much. Maybe a little mud would moisten and float into the water, but all the mud at the bottom of the new lake wouldn't affect the SG reading of the water.

Don't want to stir up a hornets' nest, but I just have to make sure I understand what is being said.

 

[boo boo]

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


And just to wade in here. 1/2 Lb of black patent???? man thats going to have a harsh ash taste IMO. That combined with the chocolate malt and oatmeal and roast Barley and a medium attenuation yeast will most likely give a high FG.
Did you mash anything with the oatmeal to convert the starch in the oatmeal?

 

[Brewno]

And just to wade in here. 1/2 Lb of black patent???? man thats going to have a harsh ash taste IMO.

I've read this before on these forums as it related to someone else's recipe.
I wouldn't know as I have only brewed three batches thus far and don't know much.
However I have seen other recipes for oatmeal stout while browsing around the net and/or magazines and I have seen quite a few with 1/2 lb of Black Patent.

When I tasted my beer after 2 weeks in bottles it tasted pretty strong and had the smell and taste of alcohol. It also tasted like a strong roasted espresso.
I tried another bottle at 16 days and I described it above in this thread...pretty much the same as the first bottle.
I had another one yesterday at 18 days, just 2 days later and the alcohol smell and taste had mellowed. So did some of the other strong flavors. It wasn't bad actually. More of a strong ale rather than a stout flavor IMO, but not bad. I'm wondering what another week or two will bring.
It does have a lingering bitter after taste. Not a bad taste just an aftertaste I've had before in other store bought beers. I had this with my first batch also and both used Fuggle hops. I wonder if it's that type of hop?
My second batch had no aftertaste and no Fuggles.

Tommy

 

[dougjones31]

I know this is a couple weeks old, but I just saw it, and I wanted to make a couple comments. I can see how, if you were to put a hydrometer into your 5 gallons of liquid (including trub) primary and take a SG reading, it might, might be different than the reading you got if you put it into your post-racked 4.5 gallons secondary.

It seems, however, that you are saying that the actual amount of volume is what is affecting the reading. That is to say, if you took your 4.5 secondary, and racked half of that into a new seperate container, you would get a higher SG reading for the 2.25 gallon liquid. I just want to clarify that, because it must be incorrect.

The reason why none of that matters is because, whether or not you've got a 5 gallon primary with a half gallon of trub, or the 4.5 gallon secondary with no trub, normally, when you take a SG reading, you're just taking a couple ounces and putting them in your measuring vessel, so there is no trub to speak of anyway.

I imagine if you swirled all the trub back into your wort, it would make a huge difference in the SG reading, but otherwise, since it is seperated out, it wouldn't make a difference. Just as pouring clear water onto a dried out mud bed wouldn't change the SG of the water that much. Maybe a little mud would moisten and float into the water, but all the mud at the bottom of the new lake wouldn't affect the SG reading of the water.

Don't want to stir up a hornets' nest, but I just have to make sure I understand what is being said.

No man.....That is not what I said. Read my posts again. I said that the decrease in volume caused by water absorption of yeast and trub reduces the volume by removing pure water thus raising the gravity of the remaining volume because the lower volume still contains all of the same solids.

 

[boo boo]

Brewno, I have only had a few comercial beers other than the BMC type so my taste for such brews in still in the expermentation stages.
I brew what I drink for the most part and I do love stout and porter. I have found that personally, a lot of black patent ( above 4oz) will give me a harsh ash taste that I don't prefer. Perhaps it is the recipies that I brew. The lower IBU's in most of my recipies might make the taste of the BP turn like that. And yes I have seen and brewed recipies that called for 1/2 Lb of BP. Didn't like the results, so I backed off on the dark malts and made something I truely enjoy.

To get to your first post on the high gravity. You added grain that needs to be mashed with base grains to convert the starch to sugars that the yeast can consume. The oats should have been mashed with 2 row or other base malts.

 

[Brewno]

I brew what I drink for the most part and I do love stout and porter.

This was my third batch and I'm starting to think that's the way I want to go, brew what I drink. However being so new to this I am curious to brew a few different styles to get a feel for the differences in the recipes and flavors/styles.
you know...the new toy
Eventually (soon) I will settle in on pale ales and ipa's which are my preferences.

To get to your first post on the high gravity. You added grain that needs to be mashed with base grains to convert the starch to sugars that the yeast can consume. The oats should have been mashed with 2 row or other base malts.

I appreciate the info although at this point it's like reading a different language I have only brewed twice before this one and the first was all extract with the next being my first partial grain. This last one was also a partial grain and didn't require mashing of any kind. While I have no doubt that mashing and partial mash etc can make for a better brew as is true also for AG, at this point I am only buying partial grain kits and following their directions.

Anyway....after three weeks the beer is very good and my first taster (other than me) liked it very much. IMO it's not what I expected an Oatmeal stout to taste like but if I didn't know what it was I would think it was a good beer.
I expect it to get even better with age.



Tommy

 

[Torchiest]

No man.....That is not what I said. Read my posts again. I said that the decrease in volume caused by water absorption of yeast and trub reduces the volume by removing pure water thus raising the gravity of the remaining volume because the lower volume still contains all of the same solids.

So you're basically saying if you brewed two batches of the same beer, and left one in a primary for three weeks, on top of the trub, and racked one to a secondary after one week, the beer left in the primary the whole time would be more concentrated, with a higher SG, without necessarily being less attenuated?

 

[dougjones31]

No.....I am saying that when you add yeast to the wort, it reproduces and as it does, it absorbs (pure)water from the wort to build the new cells. The dead cells and trub also act as a sponge absorbing more of the pure water from the wort.

The result is that the wort is concentrated because you lost .5 gallons of water and all of the dissolved solids were left in the , now smaller volume of wort.

Result--specific gravity is higher than it would be with a full 5 gallons of wort.



Think of it this way. Imagine putting a few ounces of dessicant into your wort. It will filter the water as it absorbs it. So it only absorbs pure water leaving behind anything else. Yeast and trub does the same thing.....