While racking my wine, it gave off a sulfur smell. Can I fix it?
Hydrogen sulfide (H2S) is the rotten egg odor you smell, and it usually forms at the end of fermentation. Most home winemakers won’t notice a smelly problem until the first racking. If you do smell rotten eggs, the quicker you can act, the better your chances of saving the wine. If your wine is not treated promptly, hydrogen sulfide will react with other carbon compounds in the wine to create mercaptans, and later into disulfides. These are extremely difficult to remove from your wine once they are present, so the faster you can detect and treat your wine for hydrogen sulfide, the better.
Many sources suggest that you add copper sulfate to your wine, but Midwest advises against this. While a very, very, VERY small amount of copper sulfate will take care of your H2S problem, it is poisonous. Big wineries use copper sulfate, but Midwest suggests a kinder, gentler approach, using chemicals that most winemakers already have on hand.
- First, measure the level of sulfites in your wine using the SO2 Test Kit (#40189). If the wine is deficient, treat the wine to 50 p.p.m. sulfites.
- Next, rack the wine two or three times, making sure to splash it around a lot as the wine is transferred between vessels. This aeration introduces oxygen to the wine, and will help counteract the hydrogen sulfide.
- Replace the airlock, and let it sit overnight. This should take care of the problem in most cases, but if it still stinks, perform these extra steps:
- Buy a piece of copper flashing from a home supply store.
- Hold the piece of copper in the neck of the carboy while the wine is being racked, so that the wine runs over the copper surface and into the carboy. Fine and/or filter the wine.
- By now, that stinkiness should be greatly reduced. If you STILL detect a smell, try Gelatin Finings (#8330x) in the amount stated on the package.
- Afterward, be sure to fine the wine with Bentonite (SKU 8310x) or Sparkolloid (SKU 40245) according to package instructions. Either of these will remove the copper sulfate. Then filter to remove the fining agent.
The other question to ask is why did this arise? Common causes are too much sulfites at the start, insufficient nutrients, and bacterial infection. So be sure to add Yeast Nutrients, add proper Sulfite at appropriate levels, and use a good sanitary process.