Kölsch not reaching FG

[Simon.S]

Hello
This is the first beer I'm brewing and I decided to go with a kölsch all-grain kit (Brewfather), the yeast I used is not the one specified, I used LalBrew Premium Series Kölsch, thats the only difference. I did have some problem keeping the temperature when mashing stable. First it was too low and then a bit too high. My OG also got a bit high at 1.055.

It has now been fermenting for 17 days, 2 days at 20°C and then at 15°C and now for the last 2 days again at 20°C. Problem is that the gravity is still decreasing, but very very slowly. It's now at 1.012 and the FG is supposed to be 1.007. 5 days ago the gravity was 1.015 and it's now been stable at 1.012 for 2 days. There are some activity in the airlock but only perhaps every 2 minutes.

The beer tastes good (not taking into account the lack of carbonation) and I'm quite satisfied considering this is the first time brewing. The question I'm having is can I bottle this beer (adding about 2g sugar to each 33cl bottle) or will I risk having exploding bottles? Or should I leave it fermenting longer?

//Simon

 

[Immocles]

Was your mash temp a bit high? That could leave you with a slightly higher FG, but you've gotten about 77% attenuation out of the yeast. I've never used that particular yeast, but my kolsch yeasts tend to get around that range. I'll try to mash those beers low and slow, leaving the OG in the mid 40s and pushing the FG down as far as I can.

My gut would tell me that its done, but maybe give it another day. I think the general rule of thumb is 2 stable readings 3 days apart, or something along those lines.

 

[VikeMan]

I think your expectation of a final gravity of 1.007 came from the recipe. And that's a recipe that specified 1.047 OG (not the 1.055 you got) and a different yeast strain. And your mash temp was different. All of these things could/would change the expected outcome.

My guess is that your beer is almost certainly finished attenuating.

BTW, the recipe called for OG of 1.047 and FG of 1.007, so that's 85% expected apparent attenuation.
When you got an OG of 1.055, you would normally (all other things being equal) apply 85% apparent attenuation to that and come up with 1.008. Not a big difference in this case, but I wanted to point out the idea that there's nothing special about an FG target, unless it was calculated using the actual OG and expected attenuation. Here's some general formulae for that...

Start with you recipe's OG and FG and do this...
(OG - FG) / (OG - 1)
That gives you the predicted apparent attenuation %

Then take your actual OG and do this...
((OG - 1) - ((OG - 1) x (Predicted Apparent Attenuation))) + 1
That gives you a new predicted FG.

 

[Simon.S]

Ok, thank you for quick reply. I will wait until tomorrow and take one more SG reading and if it's still 1.012 I will bottle it. Then just hoping there will be no exploding bottles.

I hope I will be able to control the temperature better during mashing next time I brew.