Carbonation: How much corn sugar to use, different when ferment under pressure?

[jwill911]

I'm still bottling, although I recently acquired a couple of corny kegs and Co2 bottle. But I have no fridge or kegerator yet so I'm still bottling.
I have a batch of Russian Imperial Stout in the fermenter which I fermented under pressure and I'm wondering if I should adjust corn sugar/bottling sugar to compensate for any carbonation that might have resulted from pressure fermentation.
Thanks,
John

 

[CascadesBrewer]

I'm wondering if I should adjust corn sugar/bottling sugar to compensate for any carbonation that might have resulted from pressure fermentation

My input is 1) Yes, you need to account for the CO2 already in the beer when you calculate your priming sugar and 2) I have no idea how this would be done. Hopefully somebody can point you at a calculator or some formulas.

 

[VikeMan]

I have a batch of Russian Imperial Stout in the fermenter which I fermented under pressure and I'm wondering if I should adjust corn sugar/bottling sugar to compensate for any carbonation that might have resulted from pressure fermentation.

What pressure and temperature did you ferment at?

 

[jwill911]

Fermenting 68-70f, started pressurizing on second day, started at 10 psi and later 5 or lower. Wasn't intending to carbonate the beer just ferment under pressure.
All is moot at this point as I bottled yesterday and used 5 oz corn sugar. Time will tell if it's too much.
Thanks.

 

[VikeMan]

Fermenting 68-70f, started pressurizing on second day, started at 10 psi and later 5 or lower. Wasn't intending to carbonate the beer just ferment under pressure.
All is moot at this point as I bottled yesterday and used 5 oz corn sugar. Time will tell if it's too much.
Thanks.

So, let's call that 5 PSI at 69F at the end. Consulting keg carbonation charts or calculators, your residual CO2 would have been about 1.04 volumes. Since a normal (non pressurized) fermentation would have landed you at about 0.8 volumes of residual CO2, you can figure you had about 0.24 "extra" volumes of residual CO2, and so would likely end up with about an extra 0.24 volumes in your final carbonated beer, which really isn't a huge difference.

Also, depending on how long the beer was exposed to atmospheric pressure (not to mention agitation) during bottling, you probably lost a bit of that extra carbonation.

 

[jwill911]

So, let's call that 5 PSI at 69F at the end. Consulting keg carbonation charts or calculators, your residual CO2 would have been about 1.04 volumes. Since a normal (non pressurized) fermentation would have landed you at about 0.8 volumes of residual CO2, you can figure you had about 0.24 "extra" volumes of residual CO2, and so would likely end up with about an extra 0.24 volumes in your final carbonated beer, which really isn't a huge difference.

Also, depending on how long the beer was exposed to atmospheric pressure (not to mention agitation) during bottling, you probably lost a bit of that extra carbonation.

Thanks for the info Vikeman. Do you mind sharing where to find keg carbonation chart. I will need to familiarize myself going forward.
John

 

[VikeMan]

Thanks for the info Vikeman. Do you mind sharing where to find keg carbonation chart. I will need to familiarize myself going forward.

There are a bunch of them out there, but all the ones I'm looking at right now seem to stop at 60F or 65F. Here's one of those:
https://www.kegoutlet.com/media/uploads_ckeditor/Carbonatin-Chart.jpg
There's also a calculator in BrewCipher that doesn't top out, because you can input whatever temperature you need to.