Ongoing sulfide issues...

[Bliorg]

GREAT discussion! Exactly what I was hoping for! Thank you, everyone, for the open exchange of ideas!

@Cap Puncher says the daily limit of copper in drinking water is 10 ppm. @sour_grapes' chart suggests that any pH below about 6.5 would allow greater than 10 ppm of copper in solution. The trend obviously must level off, because a linear extrapolation would suggest 10 million ppm at pH 3.5, or 10 grams copper per gram of solvent. But at pH 5.5, the solubility is already 100 times the limit. So how much copper actually does dissolve from the copper tube you rack with, or the pennies you rack over (for non-Canadians, lol), or the copper pad you rack through? Who knows? If you have a very accurate scale, maybe you could weigh it. 0.03 g of coper in 23 L of wine would be 1.3 ppm. It wouldn't take many solids from the wine, or wine itself, left on the copper after the racking to widely skew those results. But what we do know, is that if you prescribe copper to a patient, or use a product like Reduless, then you are guaranteed a certain dose.

Regarding the above, I *think* the cited graph is in reference to copper oxides and hydroxides, not elemental copper. I found a source, that didn't cite references (though it was from a teaching document) that said elemental copper is second in inertness to weak acids only to noble metals. I'm trying to find a better source for that, but if so, the reaction between the acids in wine and the copper in a pipe or screen would be slow and minimal. That is, if I'm interpreting this correctly. Which is always suspect.

Also, there's this anecdotally: Does copper react with acids? - Quora. I was never good at REDOX reactions.

 

[sour_grapes]

OOOOOPS! "Damn it Jim," as Bones would say, I missed that "that," and didn't make the connection. I should have known better. So glad I didn't offend you. Thanks for the correction, I appreciate you keeping me honest, and I've edited my post. I actually almost didn't post that reply, and I pray I haven't offended anyone else.

Don't worry!! We are slow to take offense.

 

[stickman]

Wine is not a pure component, it contains all kinds of stuff. Malic and citric acid are reasonably aggressive to copper, not to mention all of the other components in wine including SO2 and various salts. The solubility of copper is the limit, but the amount of copper that dissolves will depend largely on the surface area and time of exposure. In industry we put various corrosion coupons in just about all of our processes, these would be weighed periodically and you'd be surprised how quickly they disappeared. My main concern with wine is taste, so even if you don't reach poisoning levels, too much copper will probably strip some of the flavor and aromatics.

 

[Cap Puncher]

KCCam said:
@Cap Puncher says the daily limit of copper in drinking water is 10 ppm. .

Just to keep thing straight, the EPA copper limit in drinking water is 1.3mg/mL. The upper limit if daily copper ingestion from all sources (food, multivitamin, water, wine lol, etc) is 10mg (from the NIH). Upper limit is definitely different than recommended daily dosage, which is 0.9mg (again from the NIH).

Also, I wouldn't go above these allowances in wine: There is a limit in the US of 0.5mg/L and in the EU of 1mg/L. To note this unbound residual copper. The below reference notes that >0.5mg/L puts at higher risk for copper haze.

Residual Copper in Wine | Vintessential Wine Laboratories.

One last fun fact: There are lots of people now taking high doses of zinc due to COVID (for immune health). High zinc dosage overtime can lead to copper deficiency. So a bottle of a homemade wine that has been treated with copper may be just what the doctor ordered!

(edited)

 

[Bliorg]

...even if you don't reach poisoning levels, too much copper will probably strip some of the flavor and aromatics.

+1 to this

 

[Cap Puncher]

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[Bliorg]

Well, fining with bentonite cleared the haze wonderfully. Have been experiencing off-and-on sulfide odors for a couple weeks - one day nothing, then next day, can smell a little sulfide. Comes and goes. Splash racked off the bentonite yesterday. The sample I pulled smelled and tasted great, but could smell a little sulfide in the racking. I hit it with about a half dose of metabisulfite, not wanting to overdo that after all these rackings. I guess now I just sit and wait, short of another round of Reduless. Otherwise, it's ready to stabilize and sweeten and bottle.

 

[NorCal]

Though I have gravitated to using Reduless in most instances (more so because it pulls the Cu Sulfide complex out of solution since it attaches to the inactivated yeast) but I am not afraid to use copper sulfate

Guess what the active ingredient in Redulees is? Copper, a small controlled dose of copper. I’m sure there are other things too. Prevention is the best solution.

 

[Bliorg]

Update: Have checked a few times since the last racking/sulfiting, and no detectable sulfide coming off (touch wood). In fact, it's quite a nice aroma, so I'm hoping we're on this good side of this now.

As a special bonus, my son is coming home next week for Easter. This batch is one I make every year with him during his winter break, though we've never been able to bottle it together. This time around, I've been dealing with the sulfide and haze issues, but we will be able to bottle together, assuming everything comes together correctly! Going to stabilize and sweeten it and get everything ready for when he's home, then get it bottled together. I'm very happy this is working out the way it is.