by Josh Pringle
If you're a brewer, whether you call it the “Magic Bullet” or the “Holy Grail” is your choice. We choose to refer to it as the “Unicorn” of brewing because nobody has ever seen one, but everybody wants it to exist.
What is the unicorn? It is a sensor you can put INTO beer to measure the CO2 concentration.
Several companies make devices/systems that measure the pressure differential in your beer to measuring the release of CO2. Zahm & Nagel, Anton Paar, and Mettler Toledo all have ways of measuring the CO2 in beer based on calculations. Another way to measure the CO2 is by using Henry’s Law, which states:
“The principle that at a constant temperature the concentration of a gas dissolved in a fluid with which it does not combine chemically is almost directly proportional to the partial pressure of the gas at the surface of the fluid.”
Using Henry’s Law, you can measure the CO2 level in a liquid by measuring the CO2 in the head space just above the liquid, and then use an equation to compute into liquid’s actual CO2 level.
But that isn’t fast or accurate enough, nor does it take into account the difference in CO2 within the liquid sample. Aquaculture tank owners know CO2 levels are different at the top and the bottom of the tank.
The concept of the “Unicorn” is one that brewers and sensor engineers have been dreaming of for years. All you’d need is a sensor that is both gas permeable and waterproof. It would be worth billions, literally.
The difficulty of designing this sensor comes down to simply physics – how do you create a waterproof filter/membrane that is gas permeable? The Nafion filters we use are state of the art, yet they can only remove water vapor, not liquid. You have to let the gas pass through to be measured but you can’t allow water ingress. This is tricky stuff that smarter men than I have tried to resolve.
So each year at the Craft Brewers Conference we get asked dozens of times per day about dissolved CO2 sensors. And each time we respond “Oh…You want a unicorn?”
While some visitors give us a quizzical look, most understand our sarcasm immediately. They’ve been waiting for the unicorn to magically appear too.
Believe me when I tell you that when the Unicorn finally becomes reality, everyone we will let everyone know we have it.