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How long will a layer of argon or CO2 be effective in protecting the wine or must from oxygen?

TroubleShooting

Michael D. Randow — Los Alamos, New Mexico & Roger MacWilliamson — Hollister, California asks,
Q

Question #1: My carboys are 6 1⁄4 gallons (24 L). I am making mostly heavy reds and want to bulk age in glass carboys for up to twelve months before bottling. I don’t mind topping off with a small amount of similar wine every once in a while but what do you do when making an Amarone? I certainly don’t want to pour in several bottles of $65 Amarone! I have access to a cylinder of pure argon gas and want to backfill the headspace of the carboy. I would also be adding sulfite every 2–3 months to the carboy as well. How long does this technique last before you need to backfill again if you don’t open the airlock/stopper?

Question #2: How long will a layer of argon or CO2 be effective in protecting the wine or must from oxygen?

A
Since these two questions are related I will answer them together. Layering ones’ containers with argon or CO2 gas may seem like an easy, pat solution to un-topped containers. It’s heavier than air so one would assume that a nice layer of it over the wine would be just like having a completely topped container. Alas, like so much in winemaking, it is not that easy. Even if you slowly and carefully dispense the argon into the top of your container, you are still only mixing it with the oxygen, nitrogen, etc. (viz, air) that is already there. Ergo, you will never achieve a 100% inert gas blanket. Even with measuring and monitoring the dissolved oxygen content on top of the gas-layered wine, I have never found a gas layer to be able to out-perform a topped container. It may keep your wine sound for 1–4 months but beware of VA  (volatile acidity) creep, free SO2 disappearance, spoilage and oxidation thereafter. Reds fare better than whites and wines stored in cooler temperatures do better. Using argon is probably okay for
Response by Alison Crowe.