Too much copper sulfate?

[keaner]

So I fell victim to hasty and impatient cider-making this weekend...

I had a 4gallon batch of unpasteurized juice fermenting for 3 weeks at 63-68f, no camden tabs, dry champagne yeast. Being so confident I never checked on it during ferm, I opened it up today to rack and got the Hs2 rotten egg smell.

Since it had been 3 weeks, instead of adding a nitrogen shot, I went to the gent at the LHBS, and he gave me a 1% solution of copper sulfate to add before racking to secondary to clear it up.

Here comes the impatience...instead of doing some research (which would have told me just to rack and wait) I added the scantest drop of the copper sulfate, stirred and took a sample. It tastes...weird, smells less like eggs and more like corn now.
So my question to you, gentle forum reader: How concerned should I be about a slight over-use of the copper sulfate? The squeeze bottle is small, and says .5-1ml per 6gallons, and I squeezed the smallest drop I could out.

 

[andrewmaixner]

So I fell victim to hasty and impatient cider-making this weekend...

I had a 4gallon batch of unpasteurized juice fermenting for 3 weeks at 63-68f, no camden tabs, dry champagne yeast. Being so confident I never checked on it during ferm, I opened it up today to rack and got the Hs2 rotten egg smell.

Since it had been 3 weeks, instead of adding a nitrogen shot, I went to the gent at the LHBS, and he gave me a 1% solution of copper sulfate to add before racking to secondary to clear it up.

Here comes the impatience...instead of doing some research (which would have told me just to rack and wait) I added the scantest drop of the copper sulfate, stirred and took a sample. It tastes...weird, smells less like eggs and more like corn now.
So my question to you, gentle forum reader: How concerned should I be about a slight over-use of the copper sulfate? The squeeze bottle is small, and says .5-1ml per 6gallons, and I squeezed the smallest drop I could out.

If I recall correctly from chemistry class, a standard water "drop" from a dropper is 0.1mL, so 10 drops were 1mL. I presume that this liquid solution of CuSO4 doesn't have some crazy weird surface tension that would change that approximation much, since it is almost certainly an aqueous (water) solution.
So you probably put in 0.1mL, and need to add more. Contact supplier/manufacturer if in doubt, but this is probably correct. You could also pick up a eyedropper bottle, i bought a 6-pack of brown glass 2oz food-grade dropper bottles on amazon for pretty cheap.

https://www.google.com/search?q=copper+sulfate+to+remove+sulfur+dioxide+from+solution

From http://www.thevintnervault.com/index.php?p=w_m_tips&id=5781 :

Professional winemakers prefer to use a 1- percent solution of copper sulfate pentahydrate to remove H2S because the amount to copper added can be accurately measured. A simple method of removing H2S is to add enough 1 percent copper sulfate solution to produce about 0.1 ppm of copper in the wine. Then the wine should be stirred thoroughly, and after a few hours, the wine should be carefully smelled. Table 1 can be used to determine how much of the 1 percent copper sulfate solution is needed for a 0.1 ppm treatment.
One treatment is often enough, but a second or even a third treatment may be necessary for difficult cases. The wine should be left undisturbed for several days after this treatment so the copper sulfide (a very fine black powder) can settle to the bottom of the container. Then the wine should be carefully racked off the copper sulfide residue.
The following rules may be helpful when using copper to remove hydrogen sulfide odors from wine. (1) Never add copper to active fermentations. Copper sulfate added during fermentation may cause more hydrogen sulfide to be formed. (2) Only small quantities of copper sulfate solution are required, so use a pipette and measure carefully. (3) Add the 1% copper sulfate solution in small (0.1 ppm) doses rather than a single large dose. Very little copper will remain in the wine when copper sulfate is used in this way. More copper can be added if needed, but excessive amounts of copper are difficult to remove from wine. (4) Avoid adding more than 0.5 ppm of copper

 

[keaner]

Thanks for the helpful reading, to be safe I added some yeast hull slurry, which seemed to help pull any potential excess out (quite a bit of red sediment when I racked!). Unfortunately, rubbery hose smell was prevalent, so the Hs2 had gone to disulfide I believe. Next time, I'll just check during fermentation and keep some nutrient on hand!