What should my FG be?

Discuss making up beer kits - the simplest way to brew.
Rich O'York
Tippler
Posts: 11
Joined: Sun Jul 25, 2021 1:12 pm

What should my FG be?

Post by Rich O'York » Mon Jul 26, 2021 1:03 am

Newbie posting, so apologies if this is a dumb question. I'm brewing a Murphy's Stout clone and wanted to understand what sort of FG I should be aiming for. OG was 1066 and after a vigorous start to fermentation things have all but stopped at 1032. I'm thinking this is still on the high side, wondering if I need to rouse the yeast. Also wondering how you calculate the expected FG based on the ingredients used:

1.7kg Black Rock Miners Stout (can)
1.7kg Black Rock Unhopped Dark Malt Extract (can)
500g Maltodextrin Beer Improver
10g M15 Empire Ale Yeast (Mangrove Jacks)
18L water

Temperature hase been 19-21 degrees throughout the process. Anybody have any suggestions?

Cheers

Richo

User avatar
Eric
Even further under the Table
Posts: 2873
Joined: Fri Mar 13, 2009 1:18 am
Location: Sunderland.

Re: What should my FG be?

Post by Eric » Mon Jul 26, 2021 9:43 am

Final gravity depends upon more factors than ingredients, including yeast and temperature range. 75% apparent attenuation is probably a fair initial estimation, but anything between 60 and 90% is possible.

I feel that a common belief that fermentation temperature should be clamped at or to below 20 C is cause for many stalled fermentation.Assuming your readings were taken by hydrometer, I would advise you increase temperature to 23C slowly and gently rouse the yeast with a sanitised paddle or similar.

If your readings were obtained using a refractometer, because alcohol influences that, a correction factor is required for a meaningful gravity reading.

Good luck.
Without patience, life becomes difficult and the sooner it's finished, the better.

Rich O'York
Tippler
Posts: 11
Joined: Sun Jul 25, 2021 1:12 pm

Re: What should my FG be?

Post by Rich O'York » Mon Jul 26, 2021 11:31 am

Thanks Eric - the temperature range has been the natural temperature in the laundry where I brew, so I have popped it a bit nearer the radiator and gave it a bit of a stir this morning. Fingers crossed that it kicks back into life...If we were to assume a 75% attenuation rate from an OG of 1066, would we be looking at an FG of approx 1016.5?

User avatar
Cobnut
Drunk as a Skunk
Posts: 758
Joined: Fri Aug 24, 2018 4:23 pm
Location: Ipswich
Contact:

Re: What should my FG be?

Post by Cobnut » Mon Jul 26, 2021 1:07 pm

I think I would be a little concerned about the relatively small quantity of yeast you pitched.

You didn't say what brew length (i.e. volume of beer), but it looks like it's close to a typical 23L brew and at 1066 OG, 10g dry yeast is not very much.

Whether this would be (one of the) cause(s) of a high FG is far from certain, but I doubt it would have helped.

Here's hoping that rousing and raising the temperature has helped!
Fermenting: nowt
Conditioning: English IPA/Bretted English IPA
Drinking: Sunshine Marmalade, Festbier, Helles Bock, Smokey lagery beer, Irish Export StoutCascade APA (homegrown hops), Orval clone, Impy stout, Duvel clone, Conestoga (American Barley wine)
Planning: Dark Mild, Kozel dark (ish), Simmonds Bitter, Bitter, Citra PA and more!

User avatar
Eric
Even further under the Table
Posts: 2873
Joined: Fri Mar 13, 2009 1:18 am
Location: Sunderland.

Re: What should my FG be?

Post by Eric » Mon Jul 26, 2021 2:25 pm

18 litres water added to kit ingredients with 10g of yeast into 1066 is far from perfect. A second packet or a starter could make a big difference, but it is where it is. It may be difficult to get a good fermentation going from this point, but with a tail-wind it could fall a dozen points and be ready to cask or bottle and condition.
Without patience, life becomes difficult and the sooner it's finished, the better.

Rookie
Falling off the Barstool
Posts: 3550
Joined: Fri Nov 23, 2007 5:30 pm
Location: Fort Wayne, Indiana

Re: What should my FG be?

Post by Rookie » Mon Jul 26, 2021 3:34 pm

Sometimes dark extract doesn't ferment as far as you'd like.
I'm just here for the beer.

WallyBrew
Hollow Legs
Posts: 473
Joined: Sat Jan 05, 2008 11:30 pm
Location: Surrey

Re: What should my FG be?

Post by WallyBrew » Tue Jul 27, 2021 9:29 am

You have 500g of unfermentable matter in the form of maltodextrin.

This would give you about 10 degrees of gravity that will not go away so your final gravity is not likely to be lower than 1023

Rich O'York
Tippler
Posts: 11
Joined: Sun Jul 25, 2021 1:12 pm

Re: What should my FG be?

Post by Rich O'York » Wed Jul 28, 2021 11:46 am

Thanks Eric and WallyBrew - Melbourne came out of our snap lockdown today, so I was able to nick down the local brew shop to pick up some extra supplies. Looking to kick of a starter tonight and pitch it into the brew as soon as it looks ready to go...

@WallyBrew - thanks for confirming my suspicion that the Maltodextrin would mean a high FG - how do you work out the likely impact, or is that just experience talking?

WallyBrew
Hollow Legs
Posts: 473
Joined: Sat Jan 05, 2008 11:30 pm
Location: Surrey

Re: What should my FG be?

Post by WallyBrew » Wed Jul 28, 2021 1:02 pm

I’ve never used it so no experience and I’m assuming it’s a powder so maybe 100% maltodextrin

You’ve added 3.4kg of malt extract which at a guess is about 80% solids so excess SG from that is:

3.4 x 0.8 x 38.6 / 18 * 10 = 58.3 so you should get 7.7 from the maltodextrin

I just calculated the maltodextrin the same way as the syrup but assuming 100% solids:

0.5 x 38.6 / 18 x 10 = 10.7

Any of these figures could be off due to the assumptions made and possible use of incorrect factors so next time you use it make a 10% solution (10g made to 100mL) and check the gravity reading.

Rich O'York
Tippler
Posts: 11
Joined: Sun Jul 25, 2021 1:12 pm

Re: What should my FG be?

Post by Rich O'York » Mon Aug 09, 2021 1:35 pm

Well, thanks for all the advice and a quick update here...looks like repitching a yeast starter made using the SNS method has restarted a slow fermentation, dropping the SG down to 1027. I've controlled the temperature with a heat pad at 23 degrees and I think it's pretty much done now as there's not much activity and the SG has only dropped 1 point in the last 5 days.

I've also run some more calculations based on the ingredients and came up with similar numbers to the above, suggesting 10 points from the Maltodextrin that won't ferment, making the current attenuation just under 70%. Planning to take another SG at the weekend and probably bottle up on Saturday!

Rich O'York
Tippler
Posts: 11
Joined: Sun Jul 25, 2021 1:12 pm

Re: What should my FG be?

Post by Rich O'York » Sun Aug 29, 2021 12:25 am

Well it's been a bit of a journey, but after 2 weeks in the bottle, my Murphy's clone is showing some promising signs. Carbonation levels are looking good and the flavour is pretty decent too, albeit a touch green. I've attached a photo of the first pour and looking forward to seeing how it matures over time.
Thanks again for all the helpful suggestions and guidance, and for saving my stout!
Richo
Attachments
20210828_173541.jpg
20210828_173541.jpg (2.63 MiB) Viewed 3851 times

WalesAles
Falling off the Barstool
Posts: 3899
Joined: Thu Jan 24, 2013 11:07 pm
Location: South Wales UK.

Re: What should my FG be?

Post by WalesAles » Mon Aug 30, 2021 1:40 pm

Looking good Richo! =D> =D>
Hope you didn`t waste that drop spilled on your worktop. :D

WA

User avatar
PeeBee
Under the Table
Posts: 1575
Joined: Thu Jan 21, 2016 2:50 pm
Location: North Wales

Re: What should my FG be?

Post by PeeBee » Mon Aug 30, 2021 2:06 pm

Hi Rich. My advise is you repost that photo of you stout without the spilled drop.

"WalesAles" is making a heck of a mess of his PC screen trying to lick the spill up.
Cask-conditioned style ale out of a keg/Cornie (the "treatise"): https://drive.google.com/file/d/0BwzEv5 ... rDKRMjcO1g
Water report demystified (the "Defuddler"; removes the nonsense!): https://drive.google.com/drive/folders/ ... sp=sharing

WalesAles
Falling off the Barstool
Posts: 3899
Joined: Thu Jan 24, 2013 11:07 pm
Location: South Wales UK.

Re: What should my FG be?

Post by WalesAles » Tue Aug 31, 2021 7:36 pm

Tasted BLM! =D>

WA

Rich O'York
Tippler
Posts: 11
Joined: Sun Jul 25, 2021 1:12 pm

Re: What should my FG be?

Post by Rich O'York » Thu Sep 02, 2021 1:16 pm

Apologies gents, rookie error there...I think I may have been a bit hasty on the pour! Planning to have another taster tomorrow and will try to do better!
Richo

Post Reply