to break down zinc oxide

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bob syr - 06 Jul 2008 03:23 GMT

To sci.chem.analytical -

Originally this post was sent to my psoriasis group, but I didn't
receive anything from them about my question about ZnO breaking
down in my mixture.

I’ve been using zinc oxide (ZnO) as a sunscreen and it seems to work
well. But it’s hard to apply. I mixed in some commercial sunscreen
lotion with the ZnO and the mixture becomes runny, expelling several
drops of water every day. I hope the ingredients in the sunscreen
are
not breaking down the ZnO. I would hate to be using the mixture
thinking I’m getting the benefit of the ZnO when all the time I’m not
getting any good protection at all.

The ingredients in the sunscreen are: octinoxate and oxybenzone.
Would either of these break down the zinc oxide? OR, is there
another cream I could use to mix with the ZnO?

Incidentally, I’m still looking for aqueous cream. Does anyone know
how to get some.

Thanks so much for any help you would be able to give me,

Bob_Syr

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David Stone - 07 Jul 2008 13:14 GMT

In article
<8329bdfb-1ef2-4ab5-921b-9f8378919bc6@d1g2000hsg.googlegroups.com>,

> To sci.chem.analytical -
>
[quoted text clipped - 10 lines]
> thinking I¹m getting the benefit of the ZnO when all the time I¹m not
> getting any good protection at all.

I would think it more likely that the ZnO is causing the breakdown
of the organic ingredients; either way, it appears that the
formulation is unstable.

> The ingredients in the sunscreen are: octinoxate and oxybenzone.
> Would either of these break down the zinc oxide? OR, is there
> another cream I could use to mix with the ZnO?

Is there some reason you can't use magnesium stearate (used
for various cosmetics, at least) or Vaseline?

> Incidentally, I¹m still looking for aqueous cream. Does anyone know
> how to get some.

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Natural Science Forum / Chemistry / Analytical Chemistry / July 2008

to break down zinc oxide