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I've notice that after we wash & air dry our silicone nipples, frequently they will have a light whitish kind of film on the inside. This film survives boiling water sterilization too. I would then have to wash it again with a lot more soap to remove this.

Why does this happen? Is it from the milk fat?

enter image description here

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Wash/soak in vinegar and it should go away :) – Swati Feb 23 '12 at 3:16
If you wash after sterilizing, then it is no longer sterile. But you already know this, of course. – Torben Gundtofte-Bruun Feb 23 '12 at 15:17
@TorbenGundtofte-Bruun We only sterilize once in awhile...the other times we just wash with hot soapy water. – milesmeow Feb 24 '12 at 17:14

3 Answers 3

up vote 3 down vote accepted

The milk fat is easily washed away, so I would rule that out.

I think what you're seeing is the dried calcium of the tap water, especially if it seems powdery and can be rubbed off when dry. I think this is what user77907 means by scale. This is especially the case if your tap water is very hard.

You need not worry about these deposits: according to Wikipedia, the World Health Organization says that "there does not appear to be any convincing evidence that water hardness causes adverse health effects in humans."

I installed a water filter for drinking water (and for sterilization, coffee maker, etc.) in my kitchen, and all appliances as well as washed/sterilized items no longer have these deposits. If you're concerned about the purity of your tap water, I recommend this filter from APEC Water Systems; it's the best I could find, and many alternatives were much more expensive.

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It actually is no powerdery, but filmy...let me see if I can get a picture. – milesmeow Feb 22 '12 at 19:33

I think it's just scale. Nothing to worry about. Actually sterilization won't remove it but add some more...

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I'd concur with the scale idea. I live in a very hard water area and frequently see the same thing on bottles & teats. – Jamiec Feb 23 '12 at 11:40

If you are washing the bottle parts in a dishwasher it may also be any rinse aid. I've noticed a similar film after they come out of the washer. I simply give them a quick hand-wash with warm soapy water and it usually takes care of the film.

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