So, my floating thermometer broke while cooling off my wort and I didn't realize it until about an hour after I had pitched the yeast and fermentation had definitely already started.

At first I freaked out and thought I might have leaked mercury into my wort and almost threw out the batch, but then I figured out that the thermometer was lead. Alcohol based thermometers apparently have little lead beads at the bottom so the thermometer will float.

I was wary to go back into the fermenting wort and scoop out the lead pellets during fermentation so I've been letting it ferment for 5 days now. Fermentation has been strong (and it's still going) and there are no signs of any ill-effect yet. If anything fermentation seems a little more vigorous than usual.

That said, I'm not very interested in poisoning myself with lead when I drink this. When I rack this batch to secondary I'll be able to remove the lead pellets, but will that be enough? Is the alcohol enough to kill off any bad bacterias? Any other precautions I should take?

2 Answers 2


I don't know, but for the sake of peace of mind, I'd dump the batch if it was me.

The primary concern should be the ingestion of a heavy metal, not bacteria. Wort/beer is acidic, and a quick internet search reveals that lead may partially dissolve in carbonated water and other acids, and that contact with food should be avoided. The answer probably depends on how much lead you've been exposed to previously, how much you expect to be exposed to in the future, and what value you put on your health.

  • 2
    I agree, the worry is lead poisoning, not bacteria. I sort of doubt that the quantity and exposure time is enough to cause concern (as long as you rack off the yeast cake in a timely manner and ensure that no lead pellets end up in the final product), but I don't really have any basis for that assumption. You can buy home water quality kits that will measure lead concentration, if you're committed to saving the batch: amazon.com/WaterSafe-Water-Test-Kit-Lead/dp/B000Q6QWZA
    – Hank
    Commented Sep 12, 2012 at 3:34
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    A second vote for dumping the batch. Even if everything "should be ok", having a peace of mind is far more important when drinking beer than constantly convincing yourself you're not going to be lead posioned.
    – Edwin Buck
    Commented Sep 12, 2012 at 19:45

We had this same thing happen during wort chilling. I believe that most food-grade thermometers do not contain lead or mercury. We confirmed by rigging up some magnets and fishing out all of the pellets (lead is not magnetic). We also made sure to very carefully filter on transfer to remove any remaining glass. The batch turned out great!

The thermometer we broke was just like this one.

Definitely dump if you confirm that the pellets are lead.

  • Thanks. I did perform a lead test and it came out negative, which goes to back up your hypothesis that they do not contain lead or mercury. I carefully siphoned to secondary as well and plan on filtering through a .05 and .01 micron filter when I rack this to my keg.
    – Andy Baird
    Commented Oct 2, 2012 at 20:10

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