Copper bits in Potstill changed color.

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Copper bits in Potstill changed color.

Postby Winebibber » Sun Jul 16, 2017 8:13 am

Hi all,

I recently finished a 28 Lit. of Wineos plain ol sugar wash stripping run in my simple SS pot still with copper worm condenser (no reflux column right now). I used to put few pieces of thoroughly cleaned copper as boiling chips in the potstill. After successfully completing the run, I found that the copper chips were clean and shining as before, so I simply cleaned them with water and reused them for the spirit run. My low wines were also very clear.

After the spirit run, when I removed the copper bits, they were badly discolored. My final distillate started at 79% abv, I made the possibly proper cuts and collected up to 11% abv. The distillate is sparkingly clear with apparently no bad taste or smell.

I'm worried about the discoloration of boiling chips however. Is it normal or I am doing some mistake? I'll be thanklful for any guidance.
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Discolored copper bits
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Re: Copper bits in Potstill changed color.

Postby greggn » Sun Jul 16, 2017 10:36 am

What's the pH of the water used to dilute the low wines for your spirit run ? I'll bet it's slightly alkaline ( 7.4 - 7.8 ).
Last edited by greggn on Tue Jul 18, 2017 1:35 am, edited 1 time in total.
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Re: Copper bits in Potstill changed color.

Postby Winebibber » Sun Jul 16, 2017 8:39 pm

greggn wrote:What's the pH of the water used to dilute the low wines for your spirit run ? I'll bet it's slightly alkaline (7.4 - 7.8).


I did not use any water to dilute the low wines. I collected the low wines starting at 56% abv and ended at 13% abv. The average abv was 36%, so I used it straight for the spirit run.
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Re: Copper bits in Potstill changed color.

Postby NZChris » Sun Jul 16, 2017 10:30 pm

Make sure it is copper and not an alloy or plated. Does it bend and scratch like copper?
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Re: Copper bits in Potstill changed color.

Postby Winebibber » Mon Jul 17, 2017 3:09 am

NZChris wrote:Make sure it is copper and not an alloy or plated. Does it bend and scratch like copper?


Yes, I think it is pure copper. It bends and scratches easily, and is soft enough. It was a copper plate of around 2.5" diameter and 1.2 mm thick, cut into four pieces . Similar to another plate available with me posted below. I have now socked those bits in vinegar and I'll see if they can come clean after few hours.
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Another copper plate
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Re: Copper bits in Potstill changed color.

Postby Winebibber » Mon Jul 17, 2017 9:54 pm

I soaked the copper bits in vinegar for about 10 hours and cleaned them with water and a scrub. Now they are clean and sparkling. It is not clear to me why this discoloration happened. :? Any idea please?
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Bits after cleaning.
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Re: Copper bits in Potstill changed color.

Postby Saltbush Bill » Tue Jul 18, 2017 1:03 am

I have always run copper in my boiler , I have never seen it go that colour.
Did you drain the boiler and leave the copper in there for a while before removing it, oxidization could be one thing that might make it go that colour.
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Re: Copper bits in Potstill changed color.

Postby Winebibber » Tue Jul 18, 2017 7:33 am

Saltbush Bill wrote:I have always run copper in my boiler , I have never seen it go that colour.
Did you drain the boiler and leave the copper in there for a while before removing it, oxidization could be one thing that might make it go that colour.


Yes, after draining the boiler fully I let it cool down for an hour or two before picking up the bits. Does the oxidization process starts that fast? Should I worry about the quality of the distillate or continue using those copper bits in my next runs?
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Re: Copper bits in Potstill changed color.

Postby Saltbush Bill » Tue Jul 18, 2017 5:22 pm

Winebibber wrote:Yes, after draining the boiler fully I let it cool down for an hour or two before picking up the bits

I think that is your problem then, Ive seen copper go that colour when left wet and in a damp environment.

Winebibber wrote:Should I worry about the quality of the distillate or continue using those copper bits in my next runs?

Not in my opinion, looks like perfectly good copper to me.

greggn wrote:What's the pH of the water used to dilute the low wines for your spirit run ? I'll bet it's slightly alkaline ( 7.4 - 7.8 ).

Greggn would you like to explain to me why you think the PH was responsible for this issue and how it made the copper go that colour? I find it interesting that any thing and everything that cant be explained easily is blamed on PH.
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Re: Copper bits in Potstill changed color.

Postby Winebibber » Thu Jul 20, 2017 3:10 am

Saltbush Bill wrote:I think that is your problem then, Ive seen copper go that colour when left wet and in a damp environment.
Not in my opinion, looks like perfectly good copper to me.


Thanks Saltbush Bill, for the kind advise. I'll go ahead with my next batches with due care for this. :)
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Re: Copper bits in Potstill changed color.

Postby greggn » Thu Jul 20, 2017 3:59 am

>Greggn would you like to explain to me why you think the PH was responsible

>> After the spirit run, when I removed the copper bits, they were badly discolored.

Given the OP's statement above that suggested the discoloration occurred *during* the run ... not from sitting around some time afterward. Since it was a sugar wash I thought water chemistry was a reasonable culprit. I profusely apologize for my silly, uneducated assumption.
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Re: Copper bits in Potstill changed color.

Postby Winebibber » Thu Jul 20, 2017 12:14 pm

greggn wrote:>Greggn would you like to explain to me why you think the PH was responsible

>> After the spirit run, when I removed the copper bits, they were badly discolored.

Given the OP's statement above that suggested the discoloration occurred *during* the run ... not from sitting around some time afterward. Since it was a sugar wash I thought water chemistry was a reasonable culprit. I profusely apologize for my silly, uneducated assumption.


Oops! I am sorry Greggn, for your inconvenience. As a novice, I didn't recognize the importance of idle time element lapsed before taking out and examining the bits after the spirit run. I couldn't represent the whole incidence in proper words. My bad! :oops:

Thanks for all the thoughts, guys.
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