Silver Coloring On Bubble Caps

edited July 21 in General

Hi guys,

We recently did a few all-grain runs with our 150L bain-marie still (mashed, fermented & distilled in the same vessel) when we noticed a silver coloring appear on the bubble caps.

Does anyone have any idea what it is / causes it?

We have done many runs before but this is the first time fully on the grain, I suspect it may be fusel oils from the grains somehow reacting with the copper. CIP rinses most but not everything, after CIP there is a brown residue on the glass.

Flavor is amazing btw - all-grain bain-marie is the way to go for our whisky / old genever.

I'm curious how you guys normally do this:

Do you mash / ferment in another vessel and then transfer 100% (incl. solids) to the still?

Or do you filter first, or 50/50?

I feel having solids in the still definitely adds a lot to the end result. it is also a lot more work :)

Comments

  • edited July 21

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  • edited July 14

    Nobody really knows, but it’s occasionally seen.

    We get a ton of it with our locally grown rye.

    My bet is that it’s zinc-based substance that’s reacting with copper. Think of it as copper doing it’s job. It’s beautiful stuff, no?

    Not a big deal, it rinses off very easily. I haven’t dared to taste it.

    A few folks said they were going to send it off to a lab to test it, but I haven’t ever seen anyone provide the results.

  • Thanks Grim.. good to know. We did have an initial 'wtf' moment :)

  • edited July 21

    Jeff Van Horn reckons a low sulfur producing yeast and a diacetyl rest after fermentation helps reduce this phenomenon.

    Here are is comments to me the last time the sludge topic was being discussed:

    Hey Larry,

    Yes, a diacetyl rest is a temperature adjustment at final gravity. If you have the ability to control temperature, you will set the temperature at 56F for a 24 hour period. This will allow the yeast to release Diacityl and sulfur compounds lowering VDK’s (vicinal diketones) in solution. It appears that the silver stuff is sulfur buildup. After each beer strip we back flush the still to clean up some of that build up.
    Keep in mind the yeast you are using to ferment should be a low sulfur producer and producing a wash that is to high in sugars in order to get more alcohol is not a good strategy. I get that it’s real estate but an 8% wash at 500 gallons will produce a 53 gallon barrel of spirit. I have an article on VDK I will send it to you. Good to hear from you, I hope you are doing well.

    Cheers,

    Jeff Van Horn
    Moab Brewery

    Here is a link to his explanation.

    StillDragon North America - Your StillDragon® Distributor for North America

  • I get the silver all the time with grain. 56F diacetyl rest may be a step up for lagers, but not for 70F fermentations... the lower alcohol and sulfur producing yeast make sense...

    Wait until you get 'fur' in your kettle from hopped beers in an agitated kettle... that will give you a real WTF moment

  • There is at least one thread here and probably a couple on ADI regarding this. I used to get it all the time, but I can't remember the last time I saw it. As has been said, no one really knows what it is.

    It is only shiny when it is deposited, as soon as you touch it it turns to sort of black grease.

  • @jbierling said: There is at least one thread here and probably a couple on ADI regarding this. I used to get it all the time, but I can't remember the last time I saw it. As has been said, no one really knows what it is.

    It is only shiny when it is deposited, as soon as you touch it it turns to sort of black grease.

    Yep thats exactly what I saw. I've not gone into the realms of fur, and do hope not to see that :D

    We use M1 (which I'm a fan of), I rather not switch to another yeast. The diacetyl rest is a great tip, will try that.

    Thanks again guys.

  • edited July 18

    If you like your end result, don't change your process.

    Diacetyl is not a negative in whiskey, it's a critical part of flavors like butterscotch, caramel and toffee, and it has been suggested that it's oily, slick texture is a big part of the mouthfeel and finish of great whiskies. Great corn whiskies tend to be high in diacetyl as well, amping the hot buttered popcorn flavors. While diacetyl tends to be more prominent in American style whiskies, it's fairly common in European styles as well.

    Beer problems are not whiskey problems (though for me, I'd argue that if you get to the point of hot buttered popcorn, that's probably TOO much, at very high levels it starts to taste like fake cheap theater popcorn - which is literally coated in diacetyl (butter flavor) and oil).

  • edited July 18

    @grim said: If you like your end result, don't change your process.

    Diacetyl is not a negative in whiskey, it's a critical part of flavors like butterscotch, caramel and toffee, and it has been suggested that it's oily, slick texture is a big part of the mouthfeel and finish of great whiskies. Great corn whiskies tend to be high in diacetyl as well, amping the hot buttered popcorn flavors. While diacetyl tends to be more prominent in American style whiskies, it's fairly common in European styles as well.

    Beer problems are not whiskey problems (though for me, I'd argue that if you get to the point of hot buttered popcorn, that's probably TOO much, at very high levels it starts to taste like fake cheap theater popcorn - which is literally coated in diacetyl (butter flavor) and oil).

    I often use that the hot "buttered popcorn" descriptor. Maybe I need a new, better way to characterize the corny goodness that is the result of what I personally like to taste in a good corn whiskey?

    Me and Punkin drank some beer together in Shandong at one of the upstart breweries. One of the beers had some buttery notes. Punkin promptly informed me that Diacetyl was a flaw in beer. It was my favorite part lol.

    I spread butter like cream cheese frosting.

    StillDragon North America - Your StillDragon® Distributor for North America

  • edited July 18

    Diacetyl concentrations are typically higher in beer than distilled spirits, that likely has more to do with volatility during distillation. It has a boiling point of 190f, but also a pretty low flash point of 80f - that might suggest it existing predominantly in tails territory (or maybe heads), but either one would explain why diacetyl concentrations are typically lower in spirits than they would be in beer and wine, it's largely being cut away. However, it's impossible to know what the distillation profile looks like - I don't think I've ever seen anyone do a study on it.

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