OG vs FG

[Andy Alexandrakis]

Hello all new to this forum been following it for several weeks, love the great responss to different issues a new or experienced homebrewer may have. So I joined.

I haven't brewed many beers yet, like I said just started. This would be my 5th and 6th batch.
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So the two batches I brewed in the last 2 days. An imperial stout og 1.086 and a dark ipa og 1.075. Both with 2 lt. starters.

My question is I know the og that I took from a hydrometer what should i expected my final gravity would be?

I know it depends on yeast happiness and pitch rate temperature ect. So in a perfect world, by the way I am imagining a perfect world. FG should be?

Also just a helpful hint on those who have bmb and have lid issues I solved mine with tiewraps, are they not great?

Thanks
Andy

 

[JONNYROTTEN]

Depends on the malt bill,grain crush, correct water volume more than the yeast
Punch in your recipe here and youll find out the FG. The only numbers that matter here are Batch size( finished wort volume that goes in the fermenter) and efficiency. After punching in your grains adjust efficiency to match your OG and FG...pretty simple

Dont forget your hydrometer test needs to be done at the correct wort temp or it throws off your reading...usually around 60 deg

https://www.brewersfriend.com/homebrew/recipe/calculator/

 

[Rob2010SS]

Although @JONNYROTTEN is correct, there is a simpler way to tell what FG should be. The yeast you used should have an "attenuation factor". This basically means how much of the sugar will be eaten. What yeast did you use?

For example, Safale US-05 has an apparent attenuation of 81%, which means you'll have 19% of your original sugars left in the final product (approximately). Running through your example would look like this...

Imperial Stout - 1.086 OG
86*19%=16.34
FG should be about 1.016

The yeast you used will have it's own attenuation factor so you'll have to do the math, but that's how you figure it out.

 

[Smellyglove]

Attenuation factor is just a number given from the yeast manufacturer which states the degree of attenuation they got in their reference wort. For instance I don't believe a 1.086 wort with us-05 will attenuate down to 1.016 unless you go for it. The bigger beers the lower the attenuation.

It all depends on mashing, how hard you boil, yeast amount, temp regime during ferm etc etc.

I'd just say you'll end up with the attenuation you'll end up with.

 

[Andy Alexandrakis]

For the Imperial stout I used Scottish ale oyl-015 Yeast slurry.
And for the black ipa wyeats american ale II smack pack.

Again 2 liter yeast starters for both.

Thanks this helps.

 

[Smellyglove]

Well, not really for me at least. One rule of thumb is about 3/4 of OG, for "normal ales", but that might vary too. A number within 5-6-7 points is at least to me not much of interest, so I don't want to speculate, sorry.

Slurry will however usually attenuate a bit more than fresh yeast if it's been harvested properly, that's another variable.

 

[Andy Alexandrakis]

Attenuation factor is just a number given from the yeast manufacturer which states the degree of attenuation they got in their reference wort. For instance I don't believe a 1.086 wort with us-05 will attenuate down to 1.016 unless you go for it. The bigger beers the lower the attenuation.

It all depends on mashing, how hard you boil, yeast amount, temp regime during ferm etc etc.

I'd just say you'll end up with the attenuation you'll end up with.

Your right at the end of the day it is what it is. Just thought it would be nice to have an idea of what it might be. After all we have a target OG when we start out the brew, why not a FG target?

 

[Smellyglove]

Your right at the end of the day it is what it is. Just thought it would be nice to have an idea of what it might be. After all we have a target OG when we start out the brew, why not a FG target?

Because of all the variables. When we have an OG we have an OG. FG like OG is also dependent on variables, but hasn't happened yet.

What if.. "I have 5lbs of pilsner grains, what will my OG be", you with me?

 

[Renegade Brewer]

There are a lot of factors that affect your attenuation as others have stated. Your two biggest factors are going to be pitch rate and O2 absorption. For instance: my RIS starts at 1.090 with a 5000ml starter at 48 hours on a stir plate and 8 liters of O2 into solution at pitching then 5 liters of O2 12 hours after pitching I finish at 1.019 using wlp099 (high gravity.) if you are not introducing enough O2 into solution then you’re basically choking your yeast out and inhibiting their health and attention.

It sounds like you’re on the right track so far. Keep up the good brewing practices

 

[Smellyglove]

For another reference. My RIS starts at 1.115 with 3rd generation yeast and always stops at 1.032- 1.033.

 

[Andy Alexandrakis]

Because of all the variables. When we have an OG we have an OG. FG like OG is also dependent on variables, but hasn't happened yet.

What if.. "I have 5lbs of pilsner grains, what will my OG be", you with me?

Yeah I'm with you. Thanks for the advice.

 

[JONNYROTTEN]

if you are not introducing enough O2 into solution then you’re basically choking your yeast out and inhibiting their health and attention.

I'm not so sure about that.
I used to aerate the crap out of my primary I stopped and get the same results. I have a batch crashing now that I used 04 yeast on. It took off within 24 hours and was finished in 3 to 4 days. I hit 1.010. Can imagine anything better and it wasn't aerated or infected. It was a split batch and the other one I used 05. Same result but I fermented low at 62 along side the 04 batch. It took an extra day or two but finished with the same FG...unaerated

 

[Renegade Brewer]

The lag time you mentioned is a huge factor in bringing oxygen into solution. Anything with a lag time over 4-6 hours is absolutely unacceptable for us. As quickly as we turn beer around I need to be at high krausin within 6 hours and finished within 10 days at the most.

Also without enough O2 we will find not only long lag times, but also symptoms associated with under pitching such as acedaladyde, dyacital, under attenuation, stressed yeast which will not be viable enough to re-pitch for future generations, and many buds off the daughter cell which is a sign of stress and will greatly affect viability.

 

[Smellyglove]

The lag time you mentioned is a huge factor in bringing oxygen into solution. Anything with a lag time over 4-6 hours is absolutely unacceptable for us. As quickly as we turn beer around I need to be at high krausin within 6 hours and finished within 10 days at the most.

Also without enough O2 we will find not only long lag times, but also symptoms associated with under pitching such as acedaladyde, dyacital, under attenuation, stressed yeast which will not be viable enough to re-pitch for future generations, and many buds off the daughter cell which is a sign of stress and will greatly affect viability.

Commercial brewery?

In my experience a short lagtime does not always (seldom actually) mean a good end product in terms of quality of fermentation. I just brew small batches at home. If I'd see high krausen in my RIS after 6 hrs I'd freak out.

 

[Renegade Brewer]

Even as a normal homebrewer (brewed at home for 10 years twice a week which is what I consider normal) I would want to see activity within 6 hours. By listening to Jamil and John Palmer, as well as what was taught in the Brewer’s Guild, we learn that the less lag time the healthier your yeast will be. Even if you do pickup a wild bug, with a short lag time your yeast which you inoculated will become the big bug on the block and knock out any wild yeast. Plus we will see a healthy fermentation and cleaner dryer more professional tasting product.

When I judge events one thing that bugs me is drinking a sample and thinking, “yep, that’s a homebrew.” There is no reason homebrewers today can’t make the exact same quality product we can purchase with the use of the same quality products, ingredients, and equipment available to the homebrew community. The only factor would be the Brewer’s practices.

Jamil preaches this as well. We have access to the same techniques as homebrewers that professional brewers have, so why not take advantage of them?

I mostly see this on the home distilling side. I get new and seasoned distillers who say they use feed corn and bread yeast. Why would you not use the same quality ingredients professional distillers use when we are so spoiled to have access to the same exact products? There is a reason professionals use these techniques and products, so just because we are amateur brewers why not take advantage of what we learn from our professional counterparts?

 

[Smellyglove]

Even as a normal homebrewer (brewed at home for 10 years twice a week which is what I consider normal) I would want to see activity within 6 hours. By listening to Jamil and John Palmer, as well as what was taught in the Brewer’s Guild, we learn that the less lag time the healthier your yeast will be. Even if you do pickup a wild bug, with a short lag time your yeast which you inoculated will become the big bug on the block and knock out any wild yeast. Plus we will see a healthy fermentation and cleaner dryer more professional tasting product.

When I judge events one thing that bugs me is drinking a sample and thinking, “yep, that’s a homebrew.” There is no reason homebrewers today can’t make the exact same quality product we can purchase with the use of the same quality products, ingredients, and equipment available to the homebrew community. The only factor would be the Brewer’s practices.

Jamil preaches this as well. We have access to the same techniques as homebrewers that professional brewers have, so why not take advantage of them?

I mostly see this on the home distilling side. I get new and seasoned distillers who say they use feed corn and bread yeast. Why would you not use the same quality ingredients professional distillers use when we are so spoiled to have access to the same exact products? There is a reason professionals use these techniques and products, so just because we are amateur brewers why not take advantage of what we learn from our professional counterparts?

Or you over pitched massively or started out to warm for example. I can for sure if I want to see active fermentation after 6 hrs in all my beers, just pitch a lot of yeast and start out warm. I can only speak for myself, but the worst beers I've made was those which showed very early signs of visual fermentation (you can also measure activity by pH, it will drop way before it becomes visually active). They just have never seemed very clean, when I wanted a controlled flavor to them. But my setup might be very different from yours. I'm not at all afraid that if it does not start early "i'll get an infection" or such. If I get off flavors I know it was not from my visual fermentation not starting early enough.

The way I see it is that the yeast burns up lots of their energy early. I like to have it a bit more slow-controlled. I feel it's like a 800m "sprint" competition where one of the competitors acts as if it's a 100m. He has no reserves left.

 

[Renegade Brewer]

As Jamil has stated many times and John Palmer has written, it is literally impossible to over pitch on a homebrew scale. The exception maybe is the one gallon brewers, but even then it’s very hard to do.

As for fermenting too warm, on the homebrew side we’ve always either used a dedicated cold room or glycol controlled fermenters which were typically set at 62* F for ales using American strains and 60* F for our English/Irish strains. Now we are glycol chilled straight off the kettle and running into the conicals at 64* before moving to the brite tank at 34*.

Trust me though, on a 5 gallon scale when you plate your wort it is very very difficult to over pitch.

You’re absolutely correct about the beer PH. I advocate homebrewers taking a beer PH to determine how the yeast is behaving. I typically want to see the yeast buffer down to a beer PH of 4.2 within 10 hours.