I have a slightly preemie newborn baby, and when I sterilize her bottles and such in the Big, Boiling Pot of Bacterial Death, I notice a white film that appears on everything. From some web searches, it seems that this is calcium/lime deposits from hard water.

So, as much fun as it sounds to wash somewhere between 3 and 8 million tiny bottle pieces prior to sterilization, sterilize in a big pot, and then wash again to remove the calcium deposits, my strong suspicion is that there is no actual harm caused to my infant by the hard water clouding.

Are my instincts good here? Unless I know that I am right, I will still err on the side of caution and clean everything again. I just can't help but wonder if this is a total waste of time.

Edit: Any efforts taken to cite sources for claims would undoubtedly be appreciated, both by me, and by all of the space-visitors from the future!

  • 1
    Have you asked your health care provider if bottle sterilization is necessary or even preferable to careful washing alone? Commented Mar 25, 2018 at 3:46
  • 3
    @anongoodnurse Yes. Our child's pediatrician was quite insistent that we sterilize once a day. This wouldn't be my natural instinct, but I also try to be deferential to my medical practitioners if they are at least being reasonable, on the theory that allowing them to stay within their own norms also allows them to provide their best care. There are many doctors in my family, and it has been pointed out to me by some of them that medical errors become more likely as doctors get further outside of their own comfort zones. Thus, I try not to second guess my own doctors on every little thing.
    – Ben I.
    Commented Mar 25, 2018 at 3:59
  • Fair enough, and very likely much appreciated by your doctor. :) Commented Mar 25, 2018 at 4:35

1 Answer 1


The deposits from hard water are just calcium carbonate, aka chalk, and magnesium carbonate. They are completely harmless.

This report by the World Health Organisation gives a good overview of what is known on the subject. The main conclusions from studies are in section 3.3. Assuming you are getting enough calcium and magnesium from your diet (which you and your baby almost certainly are) then the effects of getting extra in hard water are pretty minimal. The extra magnesium may be correlated with lower risk of cardiovascular disease, but the effect is pretty small.

  • Thanks so much. Upvoted. Nice, helpful answer; hope you stay with us. :) Commented Mar 25, 2018 at 21:34

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .