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Copper chemical reactions?

edited February 2014 in Usage

Perplexing problem... would love an explanation.

There is a very paint like metallic silver coating on various copper bits. Its wipes off easily to the touch, floats on the surface in water, and may also be leaving a silverish hard coating on the plates. You can see this in the last picture. Scrubbing hard with a stainless brush seems to remove this coating, but Oxiclean doesn't do much.

This doesn't happen all the time. Only for "beer" mashes (malted grains) not for rum/sugars and oddly, apparently not for rye. Low wines of beer mashes are ok too.

The scrubbers are located in a glass column section after the dephlegmator and before the condenser.

Copper reacts to certain chemicals obviously, but not exactly like what I'm seeing here as far as I can tell.

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Comments

  • edited February 2014

    Saw this exact question discussed not long ago and may well of been on here. I drink to much to remember the outcome though sorry. :)]

    I do recall it was to do with tails though.

    StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

  • Did your grain supplier provide you with an analysis? Is your fermentation working off nicely?

    StillDragon North America - Your StillDragon® Distributor for North America

  • I get this when I run molasses. Wipes right off when wet. I don't let it dry before I clean it off.

  • edited February 2014

    My plates look like this after running molasses wash, must be something to do with the sulfur as its reacting with the copper not stainless.

    I clean my copper with a solution of citric acid.

    There is plenty of info about it...

    Google Search

    Wiley Online Library - The Impact of Copper in Different Parts of Malt Whisky Pot Stills on New Make Spirit Composition and Aroma (PDF)

    Maybe you have very high levels of sulfur in your mash?

  • My first reaction after seeing this the first time was that something in/on the stainless was breaking down and being deposited on the plates. But after not finding any of the substance on anything other than copper, I've mostly changed my mind on that.

    Definitely not the tails. My last run just as things started boiling I watched this silvery substance starting to cover the bottom plate.

    The grain supplier is the Country Malt Group. I don't have an analysis. The fermentation of all the different types of products is going slower than I'd like, but there are other factors at work here - temps for one.

    The thing is that the first malt mashes seem to have distilled just fine without this problem. Something is different now.

  • That looks like a Silver Nitrate reaction on Copper. That is the only thing I have ever seen that turns copper silver. The question would be how did silver get into your wash.

  • Are you sure those scrubbies are real stainless?

  • edited February 2014

    @RedDoorDistillery , I'm in the wrong business. I'm going to quit this alcohol thing and just collect silver out of my still. Seriously though, I'm not sold on sulfur being the culprit. It really does look like something different to me.

    @crystal_skull, the scrubber in that picture is a pure copper one believe or not. Looks silver doesn't it? I do have pure stainless ones too in the dephlegmator and condenser, but they look fine. But I have no proof that any of the metals in the still are or aren't what they say they are on the "label".

  • maybe its a copper plated scrubbie,

    What happens when you put the scrubbie into a citric acid solution?

  • edited February 2014

    Zinc will do this, it's a common grade school chemistry experiment. Funny I only remembered it because of the mentions of silver above - we talked about this in a section where we discussed Alchemists turning cheap metals into precious ones. Only in this case, it was just zinc plating on the copper.

    Probably not silver, but where did the zinc come from? Using any funky yeast nutrient? I'd also second the scrubber experiment above, I've seen plated scrubbers that were not advertised as such. Did you by chance test the pH of the wash?

  • edited February 2014

    @Law_Of_Ohms: I'll give it a try.

    @grim:

    Turn Copper Pennies into Silver and Gold [Chemistry Trick]

    Turning Copper Pennies Into Silver and Gold Pennies

    No yeast nutrients, just the "beer" as stated with US-05. I'll assume since no one else has seen this here, that the "zinc" or any other reactant isn't coming from the still itself. Its all standard SD stuff.

  • Have you checked the water you're using? If you're using public water sources you can usually find a water analysis. Some places have high sulfur content in the water.

  • edited February 2014

    It's not some metal coming from the unit or the scrubbies but a wash component. Although i can't remember where i saw the thread (might have been ADI?) i do remember it was explained down to wash chemistry. Lots of ways to get yeast to produce sulfur.

    StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

  • Can anyone find it ? I'm a member and have searched but nothing turned up.

    @Law_Of_Ohms: copper scrubby is looking like copper.

  • edited February 2014

    black chunks in distillate @ AD

    Couldn't find the thread i was thinking of with a quick look, but strange residues are not uncommon. I have seen the silver stuff you are talking about back in my copper pot still days. It's not coming from a metal, it's coming from the wash.

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    This is what copper packing looks like after 3 or 4 runs in an all copper VM column. You can see the all copper reflux concentrators are jet black too.

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    StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

  • If it's expected how do the big boyz keep the plates clean? Citric CIP?

    But the main questions are- affects the taste? Toxic?

  • Perhaps you could ask on Artisan Distiller if you don't get satisfaction here. There is a lot of technical minded people there.

    StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

  • edited February 2014

    Scrubber and scrubber compared to a fresh copper roll.

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  • I always blamed that silvery stuff on hops since the wash at the time was beer... will be interesting to find out what it really is...

  • It was a "beer" without hops.

    Some new info: I ran some of the leftover wash through an all copper column and... no evidence of silver.

  • Are you really trying to suggest that the stainless is somehow melting and being deposited on your plates? :-O

    StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

  • Stainless - no. Something else - I don't know. I'm out of ideas.

  • edited February 2014

    Harry gave some info on the silver deposit in this AD thread:

    As for the silver residue. It's on the tray bottoms. That tells me it's entrained (being carried) in the vapor. Could be organic (from the boiled yeast). Could be unused nutrients ...

    I had a quick look at different chemical reactions and was overwhelmed by the info. From the fermentation to heating & distilling of the wash to galvanic corrosion - all could play a part in the process.

    I'd love to hear the scientific explanation :D

  • One thing that I noticed about your pictures is that your coating seems to float on water. Is it only because of surface tension or do immersed bits come back to the surface? Any metal or metal oxide should have a density higher than 1 g/cm3and therefore not float. Is it waxy or even crumbly?

  • I'm pretty sure most of that just stayed on the surface when I immersed the plates. I don't think anything floated back up.

    Not waxy or crumbly. Maybe a bit slippery like graphite.

  • Do you have some left? Will it burn?

  • I just have one scrubby that I haven't cleaned off yet. I'll try.

  • edited February 2014

    Doesn't burn.

    Its happened again. This time with a 100% rye mash. Extremely frustrating.

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  • edited February 2014

    You've tried taking all the scrubbers out and running?

    StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

  • Yes, no scrubbers with the rye. And in any case, the scrubbers were located after the dephlegmator on the way downhill before the condenser. There couldn't have been any transfer from the scrubbers back to the plates.

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