Copper Verdigris Concerns

[jmhbutler]

Hi everyone,

I am brewing a sour beer today which will be aged for 6-9 months.

I haven't used my copper HERMS coil today and before storing it away a month ago I flushed it with some vinegar solution. Before starting today, I ran water through the coil to get rid of the slushy blue stuff (corrosion) that seems develop in the coil if left for extended periods.

After flushing till the water ran clear for a minute, I soon began my mash circulation (the opposite direction through the coil) to see a decent shot of the same blue slush go into my mash tun!!

Should I be concerned about this amount of copper, specificly verdigris poisoning?

 

[brewfun]

Probably not. In that form (copper oxide) is a yeast nutrient.

I suggest that you not use an acid to clean the copper coil. Just flush with hot (>170F) water and store it so it can drain. Use an acid sanitizer like Starsan before using it. Vinegar ( and many acids) accelerates oxidation. The longer stored, the deeper that patina is.

The only reason to use an acid rinse (phosphoric, rather than vinegar) is to remove beer stone and soften up some proteins before recirculating PBW or other soaps through it.

 

[jmhbutler]

Thanks so much for the detailed response. Couple more questions you may be able to shed insight on:

How is the creation of copper oxide different from that of copper verdigris?

Also, should I worry about the damage I've caused this one time? Could this have eaten through enough of the coil to damage it?

Finally, when rinsing after use, is my 5.4 pH sparge water sufficient or should I use more neutral water to prevent oxidization?

 

[brewfun]

How is the creation of copper oxide different from that of copper verdigris?

Fundamentally, it's not. Verdigris is just the name for the green patina. The use of Acetic acid can mean it's composed more of Copper Acetate than the Copper Chloride from just time and open air.

Also, should I worry about the damage I've caused this one time? Could this have eaten through enough of the coil to damage it?

Honestly, I can't say because there's a few variables to consider. If the patina was evenly distributed, probably no worry at all. However, if there was a pooling of it and the oxide surface area wasn't even, there may be thin spots.

Finally, when rinsing after use, is my 5.4 pH sparge water sufficient or should I use more neutral water to prevent oxidization?

That could be fine. After using a lot of copper in various mashtun designs, that pH leaves the copper shiny, but it simply dulls, rather than develops verdigris. However, the type of acid used changes how it oxidizes. I'd just use plain tap water to rinse it out while it's wet. If you can then blow air through it to clear excess water and store it so it drains, it should be just fine for the next use. You might see some darkening of the first bit of sanitizer before you use it, but this is expected as it strips that patina.

***In the scenario you presented, the oxide ended up in the mash. This presents an abundant number of opportunities for the oxide to bind with other wort and equipment constituents throughout the brewing process, thus reducing it to a safe form. This is a lot different than if it were introduced during or post fermentation. So, I'm comfortable with my advice to that extent.

HOWEVER! I'm not at your brewery and I can't taste or see the beer. If the batch tastes metallic or gives any off sensations, then the amount of oxide may exceed what can be reduced naturally and the batch should be dumped.