Dry ice can be a tremendous help for small-lot winemakers in the grape or must stage. Dry ice is really just frozen carbon dioxide gas and will cool the air (or liquid) where it’s placed whilst releasing carbon dioxide gas as it sublimates. Dry ice never melts; unlike frozen water it goes directly from the solid to the gaseous phase, releasing those white, wispy “mad scientist” bubbling mist effects. Trust me, the Wine Wizard is a fan!
I like to float dry ice pellets in a pie tin on top of my half-ton bins of must for an effective and simple CO2 blanket to help ward off bacterial infection during a cold soak. Sometimes I even put dry ice pellets (a few pounds/1 kg) in my half-ton picking bins if my grapes have a particularly long way to go from field to the winery. This cools down the bin slightly and the pooling carbon dioxide gas helps retard bacterial growth along the way. You could pop a couple of dry ice pellets into your carboys before filling them instead of gassing the headspace. However, I’d be sure to ask your supplier if their dry ice is food grade and that it smells okay. You want to be sure that any material you put into your wine is clean. Argon gas is heavier than carbon dioxide, so it is a better choice to blanket headspace with; however, it doesn’t have any of dry ice’s cooling effects and tends to be more expensive than carbon dioxide gas. All three materials have different applications and indications so I’ve been known to use all three during the course of a harvest.
Do be aware that if your wine is or gets cold enough, you may actually increase the amount of dissolved carbon dioxide gas in your wine, which may or may not be desirable to you at that stage in your wine’s life. Also, do be careful around dry ice. It can easily cause frostbite effects with prolonged skin exposure and does generate carbon dioxide gas, which can pool in enclosed and low-lying areas, presenting a hazard to pets, children and winery workers. Don’t forget that it can cause pressure buildup in closed containers; if you choose to use it in your carboys, attach a fermentation lock until you are sure that all air has been displaced and no more carbon dioxide is evolving. Otherwise, you’ll have a busted carboy, and that’s never fun, no matter how cool it looks while bubbling out all that 80s dance party fog!