Re: Streaking

John Rudiak (wizard@laplaza.org)
Fri, 13 Feb 1998 12:47:21 -0700 (MST)

On Tue, 10 Feb 1998, William Laven wrote:
> >this true and does the age of the H2O2 matter at all?
> >Stephen Harrison
>
>
> I had read long ago in Palladio's literature some stuff about Hydrogen
> Peroxide's aging properties, etc. Sincer their pre-coated paper comes in
> one "grade" the only control one has over changing contrast is through
> developers. One technique they use often is to add Hydrogen Peroxide as a
> restrainer/contrast control agent. They claimed that after extended use,
> the loosely bound molecules of Hydrogen Peroxide would make it turn into
> water to which a chemist friend of mine replied "Phoeey" (he actually
> wasn't so polite). My friend said that one need not worry about aging and
> the oxidation of Hydrogen Peroxide given the weakness of the solution and
> even suggested it might become stronger over time, though his explanations
> went over the head of me who failed high school chemistry (and it sounds
> like english, too). Perhaps someone else on the list can provide a
> chemist's explanation in lay terms.
>

The hydrogen peroxide solution we use for contrast/fog control is 3%, very
weak. It is usually stabilized with a tiny bit of sulphuric acid to
inhibit decomposition. They wouldn't do this if it didn't decompose.
Hydrogen peroxide's chemical formula is H2O2, or water with an extra
oxygen tacked onto it. I have noticed that when I put my daily ration of
H2O2 in a small dropper bottle to add to my sensitizer, when I return the
next day the rubber bulb of the dropper has swollen, Now, I haven't put a
lit match to the bottle when I opened it to test for oxygen but I'll bet
that is what it is. I also notice that if I use that peroxide it doesn't
give as much contrast boost as it did the day before. I keep my bottle of
peroxide in the 'fridge and pour out a small daily amount and then dump
what's left over. At 50 cents a pint we can afford this luxury if it's
only purpose is to make us feel better.

John