56
increase the pressure back to close to 1.25 bar. You will do that
again after a 1 day waiting period.
After clarification the vessel will therefore be near the dispense
pressure that the gas cylinder is set at and you can connect the
gas cylinder to the vessel by opening the 3-way valve. You will
then wait 1 ½ more days for a final clearing and then begin to
consume the fully carbonated beverage.
We have used a 0.5 bar pressure differential for clarification
to be sure first time users clear their beers, but this can be
reduced to 0.25 bar and clarification also achieved. Any
pressure differential less than this will likely not mix the
clarification agent well enough into the beer.
Note: We describe two methods on how to release the pressure
during a clarification. In the main instruction we use a method
for beginners where they carefully create the pressure differential
before opening the 3-way valve. In Appendix 8 we describe
another method that experienced brewers may like to try, where
they turn the 3-way valve and then release the pressure and
control clarification by the amount of bubbling that is heard. This
method requires experience with regards to knowing the amount
of vigorous bubbling that is heard (for adequate mixing) and what
a successful clarification process is. See Appendix 8 for details.
PRESSURE CONTROL FOR LOW CARBONATED BEERS
When you brew beers at a very low carbonation level, another
clarification technique is required. This is because the pressure is
so low, we cannot release gas from the vessel via the VPRV lower
than atmospheric pressure (0 bar) and so the first clarification
method described above cannot work. For example, if you’re
making an English Ale at 5°C and want a carbon dioxide content
of 3 g/l, you only need 0.12 bar pressure in the vessel, which is
very low. So you cannot release 0.25-0.5 bar out of the vessel as
described in the first method when making well carbonated beers.
In this case you need to brew with the VPRV set at about
0.25 bar above the level of carbonation you want (to allow
for the drop in pressure when the cooling is put on) and set
the gas cylinder at 0.5 bar above that (to create the pressure
differential). Then clarify as per normal and the gas bottle
pressure will force the clarification agent in the beer. The
pressure will increase in the vessel and it should release itself
out of the VPRV. When you’ve finished clarifying, you then
should release pressure out of the VPRV to the level you want
in the final beer.
You will clarify a second time using the same principle.
Once you have finished the second clarification, release the
increased gas in the vessel again to the pressure (and therefore
carbonation level) you want. Then after this, you will finally set
the gas cylinder at the same pressure which is your chosen dis-
pense pressure, and open the 3-way valve to the vessel. When
you dump the sediment bottle after 36 hours, the beer will be at
the correct pressure and carbonation.
The difference with this method is that you cannot set the gas
cylinder at the pressure you want in the final beer during
dispense until after you have clarified. With higher carbonated
beers as described in the first method above, you can set the
gas cylinder pressure at the beginning of the process and not
change it and use the VPRV to make the pressure differential
by releasing pressure from the tank.
In either case the principle is the same in that a pressure
differential of 0.25 -0.5 bar is required between the vessel (at
the lower pressure) and the gas cylinder (at the higher pressure)
in order to force the clarification agent in when the 3-way valve
is turned to the clarification pot.
MONITORING THE PRESSURE IN STEP 3 AND ADJUSTING
THE VPRV SET-POINT.
When you brew, you will need to use the pressure in the tank
during fermentation to set the VPRV at the pressure you desire.
Winding the screw down (clockwise) will increase the vessel pressure
required to release the spring and winding it out (anti-clockwise) will
lower the vessel pressure required to release the spring.
To test any new setting the vessel will need to be pressurised
and the vessel pressure gauge read when the sound of gas
emitting from the VPRV is heard. This can be done at any time
by adding gas from the gas cylinder to the vessel. However it is
easiest and results in less loss of bottle gas if performed during
fermentation when the yeast is making excess CO
2
.
So for your first brew, set the VPRV at 2 ½ turns counter-
clockwise for fermentation. This is approximately the release
point of 1.5 bar. During the first day (for ales and 2
nd
day for
lagers) the pressure will build up and you can adjust the setting.
If the vessel pressure is below or above the set-point, the VPRV
needs to be adjusted. It is important the pressure be near the
target (e.g. 1.5 bar for first time users). You don’t need to be
100% accurate as we’re fermenting at a level slightly higher
than we actually need but get as close to this as possible.
Excess gas will be released manually during the clarification
phase. The yeast makes it for free and we are in fact keeping
about only 10% of what the produce, so it’s no issue to ferment
at a higher pressure and release later.
Therefore, during fermentation, if the pressure in the vessel is
too high above target, unscrew the VPRV slightly (anti-clockwise)
until gas is heard to be emitted at the desired set-point.
If the VPRV is releasing below target (as heard and smelt off the
VPRV and read on the vessel pressure gauge), then you need to
wind the VPRV down a bit (clockwise) and let the pressure build
up and then adjust further.
If you want to set it there and then without waiting, you’ll need to
add some gas from the gas cylinder to the fermenting brew in the
vessel by turning the 3-way valve to the vessel and adding e.g. 0.3
bar pressure above the target as read on the vessel pressure gauge
and then close the 3-way again. Then unscrew the VPRV anti-
clockwise until gas is heard to be emitted at the desired set-point.
After a few brews you will know where to set your VPRV for any
desired target but you’ll likely always need some fine-tuning in
the first few days of any fermentation.
THE VPRV DURING DISPENSE
When the vessel is being dispensed, it is best to have the VPRV
at maximum to keep its release point as far away from the gas
cylinder setting as possible. So set it at maximum pressure
during dispense by screwing it right down (clockwise). When
fully wound down it will release at 2.2 – 2.5 bar, depending on
the spring tension and ambient temperature. If the VPRV is set
too close to the gas cylinder pressure during dispense, a small
amount of gas from the gas cylinder may emit out the VPRV
which is a waste of good carbon dioxide.
