Ask Wine Wizard

Dealing With A Copper Problem

TroubleShooting

Roger Mattar Corona, California asks,
Q

I have Syrah with H2S that I tried to take care of with a copper sulfate addition. After doing bench trials I found a solution but when I went to treat the entire batch I was rushing and ended up with 11 mL of 1% copper sulfate in a 15-gallon (57-L) batch. In the middle of the night I realized it was way too much. I have a 1-micron filter, would that help?

A
That’s too bad that you added more copper sulfate than you intended to. Copper is an effective, legal, and ancient (the Romans knew about its curative powers in winemaking) tool for reducing (no pun intended) stinky rotten egg defects. Hydrogen sulfide is often the culprit and ionic copper, delivered in the form of copper sulfate (CuSO4), can often help the problem. We have to be very careful because though copper sulfate is about 25% ionic copper, residual ionic copper has a legal limit in commercial winemaking (0.50 ppm Cu) because too much copper is toxic. It also can markedly change the nose and finish of a wine so that’s why it’s important to do bench trials to find the minimum dose possible that will affect the change you desire. Luckily, working out the math, and keeping in mind that copper sulfate is only 25% ionic copper if you’ve added 11 mLs of a 1% solution to 15 gallons (57-L), you’re probably right around that legal limit. You may not have to throw the wine away due to it being toxic
Response by Alison Crowe.