John,
Karen will certainly have something more to say in the fullness of time,
but there a couple of things which may be useful to keep in mind.
 
The active ingredient in baking soda is sodium bicarbonate.  One of the
ingredients in Egyptian embalming formulas was natron, a naturally
occuring form of sodium bicarbonate.  A few decades ago there were some
people who attributed the remarkable state of preservation of the linen
mummy wrappings, in part, to the presence of natron.  Linen was used for
centuries to make paper.  Therefore, sodium bicarbonate could be used to
preserve paper.
 
Subsequent research demonstrated that calcium or magnesium bicarbonates
were far safer to use with paper, and the use of sodium bicarbonate in
paper conservation went quietly away.
 
Also, gelatin emulsions are slightly acid and are unstable in an alkaline
environment.  That is why photographs and negatives are not deacidified
and should not be stored in alkaline/buffered enclosures.  Neutral seems
to be OK.  Probably.  Time will tell.
 
My thought (guess?) is that the *pinch* of baking soda which you used was
not enough, or was not present long enough, to make much difference.
 
Back to Karen.
 
Jack C. Thompson
Thompson Conservation Lab
Portland, OR
[log in to unmask]
 
 
On Thu, 19 Jan 1995, John B. Bunch wrote:
 
> Karen,
>         In my "operating on sufficient knowledge to be
> dangerous" mode, I have soaked old photographs in a tray of
> water with a pinch of baking soda with subsequent rinse.  I
> have one etching and one photograph done that way just over ten
> years ago (they were previously mounted in highly acidic
> environments and I felt I had to do something).  Seems to be
> okay if you are very tender with the originals.
> Too,photographs can be gently wiped with a clean, soft rubber
> squegee and then laid face down on fiberglass screen to
> dry--this produces about as flat a result as you can get
> without using head dryers or blotters.
>         Question:  is there a better, readily availalbe
> chemical than baking soda to neutralize the ph?
>         Thanks,
>         John Bunch
>         University of Virginia
>         [log in to unmask]
>