Re: Positive Test for Platinotype

Bas van Velzen (eland@knoware.nl)
Mon, 29 Apr 1996 10:39:51 +0100

>Thanks to all who contributed experiences on the subject of kallitype
>(im)permanence. In return, here is a little piece of (free!) knowledge -
>but I take no responsibility for the consequences of anyone using it:
>
> A positive, non-destructive test for Platinotypes - by Mike Ware.
>
>Place a tiny drop of hydrogen peroxide solution on a dark region of the print.
>(The hydrogen peroxide should be the ordinary domestic variety, so-called
>'10-' or '20-volume', i.e. 3% to 6%.)
>If the print contains a significant amount of platinum, the clear drop will
>turn white within a few seconds with minute bubbles of gas (oxygen) and may
>even effervesce ('fizz'). The platinum is unaffected, because this is a
>catalytic decomposition of hydrogen peroxide:
>
> 2H2O2 -> O2 + 2H2O
>
>The only products are harmless to the print - oxygen and water. Mop up the
>liquid with a cotton bud, and there will be no trace. The test can be
>conducted on a very small scale if you use a lens.
>

conservation police again:

may I point out that hydrogen peroxide is a rather unstable chemical. In
order to stabilize it (prevent it from decomposing into H2O freely because
there is one O2 to much) a small amount of sulphuric acid is added to give
a fake extra of H to "bind" the extra O. So in H2O2 there is a strong acid
present. In conservation when H2O2 is used a small amount of ammonia is
added to neutralise the acid. Maybe this will hamper the above mentioned
reaction. The ammonia will decompose the H2O2 (bubbles) and changes the
pH. As we all know, or should know, acids will destroy cellulose and should
therefore be avoided at all cost. So maybe a chemist could look into this
test again and give some extra information if the ammonia will change the
outcome.

Bas van Velzen

Jonge Eland papierrestauratie
eland@knoware.nl
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