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Black deposit on inside of copper still

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While testing our still we boiled some water from the water softener.
Now there are black stains on the inside of the still. This did not happen earlier when using hard water.
Has anyone else experienced this and any tips on how to clean this off ?

still black stains.JPG

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Water softeners substitute salt (NaCl) for other minerals. That could result, in part, in the formation of copper chloride dihydrate, among other things. To remove copper salts, etch with hot dilute citric acid (normally part of refreshing a still). We never use softened water, we use RO water. If you need to demineralize, then use RO. Usually there is no problem using hard water, unless it has iron in it.

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Thanks. What concentration of citric acid should I try ?

On ‎11‎/‎17‎/‎2017 at 6:33 PM, bluestar said:

Water softeners substitute salt (NaCl) for other minerals. That could result, in part, in the formation of copper chloride dihydrate, among other things. To remove copper salts, etch with hot dilute citric acid (normally part of refreshing a still). We never use softened water, we use RO water. If you need to demineralize, then use RO. Usually there is no problem using hard water, unless it has iron in it.

 

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I am worried that this might be a remnant of the manufacturing process which might contaminate the product, so wanted to clean it beforehand.

15 hours ago, ViolentBlue said:

once you do your first run, the hot acidic wash will clean that right off

 

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the black build up would most likely be copper salts, nothing to be afraid of. not likely they are remnants of the manufacturing process, but if you are really concerned do a full cleaning regiment, start with a hot caustic (PBW) wash to remove any residual oils, rinse with clean water then a cold acid to break down the copper salts.

if you have a CIP recirculate it, if not, glove up and get scrubbing by hand.

if you heat the acid it becomes more effective,  but even a mild a acid solution can do a lot of damage to the skin when hot, so be very careful.

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@ViolentBlue Did find that some of the black stuff on the towel we were trying to scrub it with, turned bluish green. So I suspect it might be copper salts as you suggested. Will try the PBW followed by acid and again PBW as you suggested. Thanks so much for your help.

1 hour ago, ViolentBlue said:

the black build up would most likely be copper salts, nothing to be afraid of. not likely they are remnants of the manufacturing process, but if you are really concerned do a full cleaning regiment, start with a hot caustic (PBW) wash to remove any residual oils, rinse with clean water then a cold acid to break down the copper salts.

if you have a CIP recirculate it, if not, glove up and get scrubbing by hand.

if you heat the acid it becomes more effective,  but even a mild a acid solution can do a lot of damage to the skin when hot, so be very careful.

 

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