Saliva changes color of paper?

[rgo...@gmail.com]

Hey everyone,

I have an idea for a demonstration I'd like to do, but I don't have
any real chemistry background, so I'm appealing to your help.

Is there a chemical that I can put onto a small piece of paper, (say
some rolling papers) that, when someone's saliva is put onto it (via
the tongue), the paper would change color?

I mean a bright color such as red.

Also, is there ANOTHER chemical that would cause the paper to change
to a different (preferably contrasting) color?

The papers should appear completely untreated and indistinguishable at
the start.

And, as should be obvious, the chemicals should be completely non-
toxic and preferably tasteless.

Thoughts?

[N:dlzc D:aol T:com (dlzc)]

Dear rgould9:

<rgo...@gmail.com> wrote in message
news:56595360-23a2-4c41...@l17g2000pri.googlegroups.com...
...

> Is there a chemical that I can put onto a small
> piece of paper, (say some rolling papers) that,
> when someone's saliva is put onto it (via the
> tongue), the paper would change color?
>
> I mean a bright color such as red.

Bright colors might be difficult.

> Also, is there ANOTHER chemical that would
> cause the paper to change to a different
> (preferably contrasting) color?
>
> The papers should appear completely
> untreated and indistinguishable at the start.
>
> And, as should be obvious, the chemicals
> should be completely non-toxic and
> preferably tasteless.
>
> Thoughts?

Kool-aid is a nearly colorless powder, which changes to bright
color when wetted. But this has flavor.

http://www.sambal.co.uk/indicators.html
... but this is only one color...

David A. Smith

[Bill Penrose]

On May 11, 9:15 pm, rgou...@gmail.com wrote:
> Is there a chemical that I can put onto a small piece of paper, (say
> some rolling papers) that, when someone's saliva is put onto it (via
> the tongue), the paper would change color?

Spit contains amylase, which breaks down starch. If you use paper
impregnated with starch, saliva will break down the starch in a few
minutes. Then, if the paper is sprayed with an iodine/iodide solution,
the spit spot will show up as a white area in a dark blue field.

Some papers come with the starch already on them as a surface
treatment, or sizing.

Another possibility is to take advantage of the buffering power of the
protein in saliva. 'Universal pH Paper' may show a change just from
spitting on it, from yellow to green. Alternately, turn the paper blue-
green by waving it over a bottle of ammonia, then spit on it.

Dangerous Bill