Check my math? Please?

[mchrispen]

I just knocked out a 12.8 P / 1.052 Bohemian Pils. Trying to work out the specific residual gravity to spunden to reach 2.5 volumes CO2. From my wonky math, I am thinking that I should close transfer when the SG is between 1.016 - 1.014, assuming a FG at 1.010, with the apparatus set to 19 psi, which should put out nearly double the CO2 - so positive pressure in vessel, purging if the apparatus is set correctly. I am using Imperial Yeast's Urkel for the first time - so I need to FFT it.

Does this make sense? Given my busy schedule the next couple of weeks, I want to make sure I transfer correctly to condition.

[Natebriscoe]

Going for a cold fermentation? 19 sounds a bit high, unless I am missing something.

[Big Monk]

1.) Calculate your residual carbonation.
2.) Establish desired carbonation.
3.) Desired - Residual = CO₂ required from extract
4.) For remaining extract:
Each °P = 2 Volumes CO₂
Each S.G. = 0.51 Volumes CO₂

Example:

Residual = 1.343 Volumes CO₂
Desired = 2.5 Volumes CO₂

2.5 - 1.343 = 1.157 Volumes CO₂ needed
Final gravity = 1.010

((((1.157/0.51)/1000)+1) + 1.010 = 1.012

Transfer Gravity = 1.012

These are the calculations I used on my bottle spunding paper. Full disclosure: I am not a kegger. The calculations should hold true regardless. Many do it by based on their own empirical experience but the calcs should get you started.

[Natebriscoe]

Would you not just use the force carbonation temp/psi chart for spunding?

[Natebriscoe]

[Big Monk]

The lack of interest and a subsequent major revision made keeping multiple forms of the sheet impractical.

The spreadsheet as it stands now is a purpose built tool that isn't available for public consumption any longer.

[mchrispen]

> Each S.G. = 0.51 Volumes CO₂

That was what I was missing. Thanks!

[Weizenberg]

In principle you only want to transfer as little yeast as necessary.

That's why yeast dumps are often performed in ZKF's before it meets its final resting place.

Lacking the backup of a laboratory, there is a bit of feel one needs to develop with all this. It will take a few gos but the results will be worthwhile

[mchrispen]

Thanks Nico.

I have a microscope and hemocytometer. Planning to check cell counts along the way. I ferment in 1/2 barrel conicals, so will pull yeast before I closed transfer... I plan to reuse it immediately anyway.

@Natebrisco >Would you not just use the force carbonation temp/psi chart for spunding?

I tried this in the past. Doesn't work all that well... it is damned hard to calibrate the spund apparatus properly. I would prefer to over carb than under, and I have long lines on my kegerator to deal with the serving side (a habit from my saison addiction).

[Weizenberg]

You still want to transer 15*10^6 cells per ml. But that's active yeast in suspension, not dead sludge (Source: Annemueller)