High FG

Australia & New Zealand Homebrewing Forum

Help Support Australia & New Zealand Homebrewing Forum:

Jolls

Well-Known Member
Joined
28/3/20
Messages
53
Reaction score
16
G'day Punters
I have ad dilemma that I trust someone with more experience can assist me with. I have two beers int he fermentation fridge - A 1931 Tooths White Horse Ale clone based on the recipe in Bronzed Brews and a Vanilla Milk Stout. The calculated OG/FG for the pair was 1.052/1.008 and 1.047/1.011 respectively. The Stout went down a week after the The White Horse Ale.

The OG into the fermenter for both was 1.044. Yeast Safale English Ale S-04 yeast pitched at 19C. The Ale fermentation appeared to stall at 1.017 and the Stour at 1.020

I swirled them and raised the temp to 22C for a week - no change.
I added additional S=04 yeast and could small the carbondiaxide being relaeased. Five days later curring gravity readings remain at 1.017 amd 1.020 respectively.

Water is rainwater and I have yet to do an analysis of it. I did not check the PH level as I have had no problems with any of my previous brews. something I must do in future.

The Stout has 150g of lactose tht ws added to the boil.

Any thoughts on why the FG is so high?

Plan is to crash and keg it this weekend (subject to the wsdom inparted here)

Thanks in advance fro your guidance.

Cheers n Beers

Jolls
 

MHB

Well-Known Member
Joined
1/10/05
Messages
6,816
Reaction score
4,282
Location
Newcastle
Ok, assuming you made 23L of wort the Lactose will have added around 0.0026 to your FG. Given how hard it is to read an Hydrometer to four places that probably accounts for the extra gravity in the stout.

If the White Horse went from 1.044 to 1.017 you have an apparent attenuation of (44-17)/44=61%, well under the 75+% you would expect from S-04.
The most obvious place to look is at your mash temperature. Have you calibrated your mash thermometer, odds on its out and you mashed hotter than expected, making more unfermentable dextrins than intended.
Been saying for a long time that every brewer should have a decent quality Lab thermometer that they use to check everything else, especially dial thermometers.
Mark
 

Jolls

Well-Known Member
Joined
28/3/20
Messages
53
Reaction score
16
Ok, assuming you made 23L of wort the Lactose will have added around 0.0026 to your FG. Given how hard it is to read an Hydrometer to four places that probably accounts for the extra gravity in the stout.

If the White Horse went from 1.044 to 1.017 you have an apparent attenuation of (44-17)/44=61%, well under the 75+% you would expect from S-04.
The most obvious place to look is at your mash temperature. Have you calibrated your mash thermometer, odds on its out and you mashed hotter than expected, making more unfermentable dextrins than intended.
Been saying for a long time that every brewer should have a decent quality Lab thermometer that they use to check everything else, especially dial thermometers.
Mark
 

Jolls

Well-Known Member
Joined
28/3/20
Messages
53
Reaction score
16
Thanks Mark
I paid particular attention to the mash temperature but I can't vouch for the calibration of the thermometer. I was concerned that the temperature was dropping too quickly in the esky I use as a mash tun. I added boiling water to bring it back up to temp at the 30 minute mark for both brews. I have just purchased a robobrew so trust I will have better control for the next brews.

So my next steps in building my system and knowledge base should be:

Lab thermometer
Water test

I guess it is now a matter of keging and enjoying what I have and brewing it again down the track to se if I can make a better version. Taste out of the fermenter for both brews is good so I expect the end result to be enjoyable despite the dissapointing FGs.

Cheers n Beers
Jolls
 

MHB

Well-Known Member
Joined
1/10/05
Messages
6,816
Reaction score
4,282
Location
Newcastle
My local sells a good glass Lab thermometer for $15. Just be a little careful when you select one. They range from complete crap to ridiculously precise and expensive (say $400), somewhere in between is a good call.

If you look after it it will last a lifetime and is a great investment.
Don’t know where you are located or who you get your stuff from, but choose carefully and it will serve you well.
Mark
 

Jolls

Well-Known Member
Joined
28/3/20
Messages
53
Reaction score
16
Hi Brainstrust,

Need a bit of help based on the wisdom of more experienced brewers.

I took Marks advice and purchased a good thermometer. Threw down the next brew and was super vigilant with the temperature in the new Brewzilla 4. Had the brew in the fermenter for 10 days SG 1.034, and there it has remained for the last three days. Target FG is 1.008. For the life of me I couldn't figure out the problem. Took a reading this evening 1.034 - so I took out the old Coopers Hydrometer and low and behold reading 1.011. So I look back and the high FG correlates to switching from the trusty floaty hydrometer to a handheld ATC. Has anyone come across this before?

Probably no issue with the previous brews either - they taste great out of the keg and have the right effect so I guess the hand held was the problem all along.

I will recheck the calibration of the handheld hydrometer but in the meantime taking one step backwards and reverting to what I know.

About to start my first lagering process!

I'll let you know how I get on.

Cheers n Beers

Jolls
 
Last edited:

MHB

Well-Known Member
Joined
1/10/05
Messages
6,816
Reaction score
4,282
Location
Newcastle
Well if you used a Refractometer once the ferment has started that would be the answer.
How a Refractometer works is it measures how far the sample bends light. Water bends light (refracts it) a certain amount, Alcohol a different amount and Sugars another set of different amounts. Brewing refractometers are all calibrated against white sugar (admittedly wort is slightly different but not much). Basically a 10% W/W (i.e. 100g Sucrose 900g Water) solution of sugar in water will be 10 Brix or Plato, it will have a gravity of 1.040 (or very close)
As you ferment, sugars mainly Maltose, converts to Alcohol and CO2. You end up with a three part problem, you can calculate the Gravity but it requires mathematic manipulation of the numbers. There are plenty of online calculators and a few good explanations of the equations they use if you want to understand the process better. Play with a couple and find one you like, you have the numbers to hand to plug in. Makes using a Refractometer pretty easy and they are convenient for quick checks.
Mark
 

Jolls

Well-Known Member
Joined
28/3/20
Messages
53
Reaction score
16
Thanks Mark
You are a lifesaver. Take two days off next weekend!

A definite lightbulb moment for me. I had wondered about the how the refractometer compensated for the "dirtiness" of the brew and rationalised that it was measuring the light refraction from the sugars. I assumed that the calculator worked the same post fermentation but did not account for the difference between sugars and alcohols. It did not dawn on me until yesterday that the high FG readings only started when I changed to using the refractometer.

I plugged the details into a calculator and it correlates with the calculated SG. Same for the two previous brews. So it had nothing to do with my technique (although the lab thermometer tip has certainly improved my process). As a tradie the old adage that a poor tradesman blames the tools is always in my mind. I went straight to thinking my process was bad as opposed to the readings from the tool I was using. It is not that the tool was bad - just the tool taking the readings was didn't educate himself well enough.

This has taken a load off mind. I am enjoying my Vanilla Milk Stout more now that I know it turned out right! Amazing that a change in mindset can change how you feel towards an inanimate object like beer.

Cheers n Beers

Jolls
 

Latest posts

Top