Silver Coloring On Bubble Caps

Stinky

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 :)

Stinky

photo's

grim

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.

Stinky

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

Smaug

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.

CothermanDistilling

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

jbierling

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.

Stinky

@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.

grim

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).

Smaug

@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.

grim

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.

SingleMaltYinzer

@Smaug and I talked about this a bit tonight. I'll let him talk about what he found. I thought it was tails. I don't know though. I have had this happen to me with copper scrubbies in a column.

But something curious that is one of those it's right in our face but we didn't think about it: The silver material is only found where there is no liquid flowing. If you zoom in the interior facing side of the downcomers are free of the material, that might be where most of the liquid comes out of the it. The outside facing is coated. it's not on the bottom of the downcomers either, where reflux would gather and linger. It's also not on the top of the bubble plate where the liquid boils, but it is on the bottom where there is no liquid. It is interesting that the material does not form or is dissolved by liquid. And that liquid is composed of the same material in vapor form. Any solvent action should remove it with just vapor as it's the same material. Maybe it's the physical action of the liquid that removes it. A small amount of reflux might not be able to do it so that why it is only showing in areas that aren't touched by liquid. And we might have the same thing with copper helmets and tubing but we don't notice as much as there is enough reflux to physically remove it. At the end of the run there's nothing left to see. If the material isn't adhesive or cohesive it should not require much physical effort to displace or remove.

Maybe may be more common than we think.

grim

Agree, it rinses or wipes away very freely. With more robust action in the column, it would probably not ever be seen. Especially so in enclosed columns with small sight glasses (we might be noticing this more readily just because of glass columns as well).

jbierling

I think I first mentioned this here about 9 years ago. It is hard to believe no one really knows what it is yet.

Copper chemical reactions?

Smaug

@jbierling said: I think I first mentioned this here about 9 years ago. It is hard to believe no one really knows what it is yet.

Copper chemical reactions?

Time flys.

I'm wondering if it's origin is created by over cooking lesser grains in the grain bill that are mixed in with corn? Basically breaking down proteins ( and the like) that would otherwise be cooked with less heat for less time were it not mixed in with corn?

Thoughts?

grim

Wasn't someone sending off a sample to a lab for analysis? I thought there was a big to-do about that, then nobody ever heard back.

My money is still on some kind of Zinc compound (yes, 9 years later). It's common enough in grain and rapidly taken up by yeast during fermentation (highly bioavailable/reactive). The formation on copper has got to mean it's a copper catalyzed reaction (as opposed to a precipitate being formed during distillation/condensation).

SingleMaltYinzer

@grim said: My money is still on some kind of Zinc compound (yes, 9 years later). It's common enough in grain and rapidly taken up by yeast during fermentation (highly bioavailable/reactive). The formation on copper has got to mean it's a copper catalyzed reaction (as opposed to a precipitate being formed during distillation/condensation).

Not catalyzed but after google searching this a bit yes, it looks like two different copper/zinc reactions might be the culprit. I wouldn't say case closed, but it's a good lead. Zinc is reactive to copper oxide and copper sulfate, both of which are present on the copper in a still.

Reacting zinc and copper(II) oxide @ RSC Education

Copper oxide and zinc metal react together in an exothermic reaction to produce zinc oxide and copper. ... the white powder (zinc oxide) is yellow when hot and white when cool

And also: Redox reaction from dissolving zinc in copper sulfate

https://www.youtube.com/watch?v=wVMe8ZmCZo0

SingleMaltYinzer

Zinc and compounds @ DCCEEW

Zinc sulfate is soluble in water, methanol and glycerol. It is insoluble in alcohol. Insoluble sulfates are formed when zinc sulfate is combined with lead, barium, strontium, and calcium salts.

This would explain why its so easy to clean.

jbierling

@grim said: Wasn't someone sending off a sample to a lab for analysis?

I think I said I was going to try to do that, but collecting a sample of the silvery stuff was impossible (at least for me). As soon as you touch it, it turns to black oily goo that is completely unlike what you wanted to sample.

And then the problem (for me) mostly went away. And was it even a problem? It didn't seem to affect the end result.

SingleMaltYinzer

@Smaug said: I'm wondering if it's origin is created by over cooking lesser grains in the grain bill that are mixed in with corn? Basically breaking down proteins ( and the like) that would otherwise be cooked with less heat for less time were it not mixed in with corn?

As you said on the phone this would lead to excess DMS - Dimethyl Sulfide. The thing here is that it's sulfide, not sulfate.

https://www.youtube.com/watch?v=FCILypZQP3k

I think @grim and @Smaug are on the right track. I'm just not sure how to link all these things together yet.

grim

My 100% rye mashes generate the most of it, compared to just about everything else we do, especially rums which generate nearly none of it. Never, ever, have I seen it form on a spirit run (I could be wrong, those are always really early mornings for us).

SingleMaltYinzer

@grim said: Never, ever, have I seen it form on a spirit run

The same here. That's weird though. If something is present in the vapor in a wash/stripping run, should it not be present in the spirit run? How could it not be present? If it is vaporized then it would also be present in the low wines.

Glenndog

I get it all the time and I only make rum. Only on the stripping run though. I use straight blackstrap molasses, no sugar.