Carbonating

The step with the most equipment and the most immediate physical risk.

Cold first

Carbon dioxide dissolves far better in cold liquid than warm.

Chill to near zero before carbonating. Trying to carbonate a warm liquid wastes gas, takes far longer and produces a drink that foams uncontrollably when filled.

This is the single biggest factor in whether carbonating works, and it is the one small operations most often compromise on because chilling capacity is expensive.

Setting the level

Apply CO2 at the pressure corresponding to the volumes you want at the temperature you are working at, and give it time to equilibrate.

The pressure needed rises with temperature, and the pressure the bottle will see later also rises with temperature, which is why the specification has to name both the volumes and the reference temperature.

Agitation speeds it up and it is easy to overshoot that way; patience is more reproducible.

Counter-pressure filling

Filling carbonated liquid into an open bottle loses gas and foams, which gives you an under-carbonated product and an inaccurate fill.

A counter-pressure filler pressurizes the bottle first so the liquid enters without degassing.

Below that, the practical answers are to fill as cold as possible, as gently as possible, and to accept some loss in the specification.

Checking it

Measure carbonation rather than judging it, with a pressure and temperature reading on a sealed sample.

Check a bottle from the start, middle and end of a run, because carbonation drifts as a tank empties and warms.

And check a bottle after it has been warm, which is the pressure the package actually has to survive and the number the pressure rating has to be chosen against.

References