How do I know when its half way?

[rferguson61]

My first lager is fermenting right now and I'm planing on doing a diacetyl rest. Over been told to do the rest when its about half way through fermentation. I know it has to do with the gravity. OG was 1.060 I believe (can't remember off the to of my head but out was right around there) How do I know what the FG should be?

 

[Token]

Excellent question! I was wondering the same thing. Did a California Common about a month ago; my first lager. I was wondering how the heck I was supposed to figure it out other than keep taking hydrometer readings, but I didn't want to mess with it during fermentation. I just did the rest when it looked like the activity was about done. Not at all scientific, but it was my first "lager." I was just winging it. Looking forward to some words of wisdom on this.

 

[bja]

Wait til the krausen falls. It's really not that critical.

 

[Yooper]

Actually, half way is too soon! Generally, you want the beer to be about 75% or greater finished. SG readings will tell you, but you can see for yourself that fermentation is slowing down. The krausen may be falling/fallen, the airlock bubbles more slowly, although the beer is still cloudy from yeast in suspension. That's the time to do the diacetyl rest, and if you took an SG at that time it should be in the 1.020ish area.

 

[rferguson61]

Actually, half way is too soon! Generally, you want the beer to be about 75% or greater finished. SG readings will tell you, but you can see for yourself that fermentation is slowing down. The krausen may be falling/fallen, the airlock bubbles more slowly, although the beer is still cloudy from yeast in suspension. That's the time to do the diacetyl rest, and if you took an SG at that time it should be in the 1.020ish area.

How do I figure that out tho? How am I suposed to know what the FG is before its done.

 

[Yooper]

Seriously? Somebody hit "report this post" to alert the admin that my above post was a bad post? TWICE? Geez. Thanks alot.

 

[Yooper]

How do I figure that out tho? How am I suposed to know what the FG is before its done.

That's the time to do the diacetyl rest, and if you took an SG at that time it should be in the 1.020ish area.

Better if it's BOLD?

 

[BierMuncher]

Seriously? Somebody hit "report this post" to alert the admin that my above post was a bad post? Geez. Thanks alot.

I saw that too Yoop. Probably mistook the report post for "reply".

 

[Revvy]

Maybe they meant to click on

and got it mixed up.....Or did they leave a comment in the box?

 

[Token]

Yoop, I found your reply to be quite reassuring. I think I might have done my d-rest at a pretty good time. And now I have a better idea of when to do it next time. THANKS!!

 

[theredben]

If you really want to know when to perform the D-rest, you can do a forced ferment test.

HBT Wiki: Fermenting Lagers

The "Forced Ferment" is about 3/4 of the way down. It is a bit of extra work, but some of us just like knowing.

 

[rferguson61]

Im not asking you to TELL me WHAT it is...im asking you to tell me HOW to figure it out. The math. Sorry I thought I made that clear enough. My bad.

 

[bja]

Im not asking you to TELL me WHAT it is...im asking you to tell me HOW to figure it out. The math. Sorry I thought I made that clear enough. My bad.

There's all kinds of software available which will calculate the expected FG for you. Some of it is even free.

Or, the yeast description gives an attenuation percentage which can be used to calculate the expected FG if the OG is known.

 

[rferguson61]

There's all kinds of software available which will calculate the expected FG for you. Some of it is even free.

Or, the yeast description gives an attenuation percentage which can be used to calculate the expected FG if the OG is known.

So say attenuation is 75% you multiply the numbers after the decimal point by .75? So if OG was 1.060 then you'd do .060×.75=.045 which would give you 1.015. Did I do that right?

 

[bja]

So say attenuation is 75% you multiply the numbers after the decimal point by .75? So if OG was 1.060 then you'd do .060×.75=.045 which would give you 1.015. Did I do that right?

Yes!

 

[rferguson61]

Yes!

Thanks that's what I was looking for!