Any Ideas as to What This Is?

[Kyjd75]

Although this occurred with a bottle of 21 year old El Dorado rum, I am posting here because of increased exposure, and because the question is not about the rum itself, but what happened with the stainless steel stopper we were using to seal the bottle with.  Synopsis:  21 yr El Dorado rum, opened about 3 years ago and about half a bottle consumed at that time.  Then, cork broke and so we used a stainless steel bottle stopper to "seal" the bottle.  We put the bottle aside and never looked at it again until a couple of days ago.  Decided to use it to spike some egg nog and discovered this crap all over the stopper and the inside of the neck of the bottle.  We were spooked and not only did we not use the rum, we poured it out.  Here are some pictures of the stopper.  The white stuff is hard like barnacles on a hull.  Won't wash off.  What is it?

 

 

[flahute]

Could be calcites of some sort? This looks like galvanic action which is the result of dissimilar metals being next to each other. Not sure why that would happen of course since there was only one metal unless that rum was funky enough to have some metals come through distillation. Copper is the likely culprit but stainless and copper are generally compatible. May have been some other metal in there.

All theory here as I've never seen this before.

[smokinjoe]

Does it have a smell?  

[Kyjd75]

35 minutes ago, smokinjoe said:

Does it have a smell?  

No smell.

[RWBadley]

Not all 'stainless' is the same. Some will react more readily. Looks like some sort of galvanic action going on. 

I suspect the stopper wasn't designed for much more than temporary use in bottle. You were right to be wary of drinking the contents after seeing that in the bottle

 

 

[smokinjoe]

Rum, you say...?   Well, based on some of the descriptors I've heard about "good" Rum, I'm guessing that stuff is perfectly normal and desirable...  

[BigRich]

So let me get this straight...you got a bottle of "rum" from south of the border and as it evaporates is leaves a white powdery substance behind. Did you call Crockett and Tubbs?


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[Kane]

It's the embodiment of ancient rum deities' wrath for mixing El Dorado 21 with eggnog.

 

On a more serious note, the definition of "stainless steel" is quite loose already, and with cheap equipment like this that's produced who knows where under what quality control conditions, you can expect a lot of interesting metal reactions. Been there done that.

[Richnimrod]

48 minutes ago, Kane said:

On a more serious note, the definition of "stainless steel" is quite loose already, and with cheap equipment like this that's produced who knows where under what quality control conditions, you can expect a lot of interesting metal reactions. Been there done that.

I bet this has much more to do with the (supposedly) stainless than anything else.

I woulda tossed all of it, as well.   Not worth getting poisoned for the saving of a pint of hooch.   ...And don't discount the sparing of the hopefully-decent eggnog that you preserved by not adding this to it.

[tanstaafl2]

It does make a good advertisement for using cork, whether real or artificial, for closing bottles that have lost their cork!